This class is for elements that receive buffers in an undesired size.
While for example raw video contains one image per buffer, the same is not
true for a lot of other formats, especially those that come directly from
a file. So if you have undefined buffer sizes and require a specific size,
this object is for you.
An adapter is created with gst_adapter_new(). It can be freed again with
g_object_unref().
The theory of operation is like this: All buffers received are put
into the adapter using gst_adapter_push() and the data is then read back
in chunks of the desired size using gst_adapter_map()/gst_adapter_unmap()
and/or gst_adapter_copy(). After the data has been processed, it is freed
using gst_adapter_unmap().
Other methods such as gst_adapter_take() and gst_adapter_take_buffer()
combine gst_adapter_map() and gst_adapter_unmap() in one method and are
potentially more convenient for some use cases.
For example, a sink pad's chain function that needs to pass data to a library
in 512-byte chunks could be implemented like this:
|[
static GstFlowReturn
sink_pad_chain (GstPad *pad, GstObject *parent, GstBuffer *buffer)
{
MyElement *this;
GstAdapter *adapter;
GstFlowReturn ret = GST_FLOW_OK;
this = MY_ELEMENT (parent);
adapter = this->adapter;
// put buffer into adapter
gst_adapter_push (adapter, buffer);
// while we can read out 512 bytes, process them
while (gst_adapter_available (adapter) >= 512 && ret == GST_FLOW_OK) {
const guint8 *data = gst_adapter_map (adapter, 512);
// use flowreturn as an error value
ret = my_library_foo (data);
gst_adapter_unmap (adapter);
gst_adapter_flush (adapter, 512);
}
return ret;
}
]|
For another example, a simple element inside GStreamer that uses GstAdapter
is the libvisual element.
An element using GstAdapter in its sink pad chain function should ensure that
when the FLUSH_STOP event is received, that any queued data is cleared using
gst_adapter_clear(). Data should also be cleared or processed on EOS and
when changing state from #GST_STATE_PAUSED to #GST_STATE_READY.
Also check the GST_BUFFER_FLAG_DISCONT flag on the buffer. Some elements might
need to clear the adapter after a discontinuity.
The adapter will keep track of the timestamps of the buffers
that were pushed. The last seen timestamp before the current position
can be queried with gst_adapter_prev_timestamp(). This function can
optionally return the amount of bytes between the start of the buffer that
carried the timestamp and the current adapter position. The distance is
useful when dealing with, for example, raw audio samples because it allows
you to calculate the timestamp of the current adapter position by using the
last seen timestamp and the amount of bytes since.
A last thing to note is that while GstAdapter is pretty optimized,
merging buffers still might be an operation that requires a malloc() and
memcpy() operation, and these operations are not the fastest. Because of
this, some functions like gst_adapter_available_fast() are provided to help
speed up such cases should you want to. To avoid repeated memory allocations,
gst_adapter_copy() can be used to copy data into a (statically allocated)
user provided buffer.
GstAdapter is not MT safe. All operations on an adapter must be serialized by
the caller. This is not normally a problem, however, as the normal use case
of GstAdapter is inside one pad's chain function, in which case access is
serialized via the pad's STREAM_LOCK.
Note that gst_adapter_push() takes ownership of the buffer passed. Use
gst_buffer_ref() before pushing it into the adapter if you still want to
access the buffer later. The adapter will never modify the data in the
buffer pushed in it.
Last reviewed on 2009-05-13 (0.10.24).
Creates a new #GstAdapter. Free with g_object_unref().
a new #GstAdapter
Gets the maximum amount of bytes available, that is it returns the maximum
value that can be supplied to gst_adapter_map() without that function
returning NULL.
number of bytes available in @adapter
a #GstAdapter
Gets the maximum number of bytes that are immediately available without
requiring any expensive operations (like copying the data into a
temporary buffer).
number of bytes that are available in @adapter without expensive operations
a #GstAdapter
Removes all buffers from @adapter.
a #GstAdapter
Copies @size bytes of data starting at @offset out of the buffers
contained in @GstAdapter into an array @dest provided by the caller.
The array @dest should be large enough to contain @size bytes.
The user should check that the adapter has (@offset + @size) bytes
available before calling this function.
a #GstAdapter
the memory to copy into
the bytes offset in the adapter to start from
the number of bytes to copy
Flushes the first @flush bytes in the @adapter. The caller must ensure that
at least this many bytes are available.
See also: gst_adapter_map(), gst_adapter_unmap()
a #GstAdapter
the number of bytes to flush
Gets the first @size bytes stored in the @adapter. The returned pointer is
valid until the next function is called on the adapter.
Note that setting the returned pointer as the data of a #GstBuffer is
incorrect for general-purpose plugins. The reason is that if a downstream
element stores the buffer so that it has access to it outside of the bounds
of its chain function, the buffer will have an invalid data pointer after
your element flushes the bytes. In that case you should use
gst_adapter_take(), which returns a freshly-allocated buffer that you can set
as #GstBuffer memory or the potentially more performant
gst_adapter_take_buffer().
Returns #NULL if @size bytes are not available.
a pointer to the first @size bytes of data, or NULL
a #GstAdapter
the number of bytes to map/peek
Scan for pattern @pattern with applied mask @mask in the adapter data,
starting from offset @offset.
The bytes in @pattern and @mask are interpreted left-to-right, regardless
of endianness. All four bytes of the pattern must be present in the
adapter for it to match, even if the first or last bytes are masked out.
It is an error to call this function without making sure that there is
enough data (offset+size bytes) in the adapter.
This function calls gst_adapter_masked_scan_uint32_peek() passing NULL
for value.
offset of the first match, or -1 if no match was found. Example: <programlisting> // Assume the adapter contains 0x00 0x01 0x02 ... 0xfe 0xff gst_adapter_masked_scan_uint32 (adapter, 0xffffffff, 0x00010203, 0, 256); // -> returns 0 gst_adapter_masked_scan_uint32 (adapter, 0xffffffff, 0x00010203, 1, 255); // -> returns -1 gst_adapter_masked_scan_uint32 (adapter, 0xffffffff, 0x01020304, 1, 255); // -> returns 1 gst_adapter_masked_scan_uint32 (adapter, 0xffff, 0x0001, 0, 256); // -> returns -1 gst_adapter_masked_scan_uint32 (adapter, 0xffff, 0x0203, 0, 256); // -> returns 0 gst_adapter_masked_scan_uint32 (adapter, 0xffff0000, 0x02030000, 0, 256); // -> returns 2 gst_adapter_masked_scan_uint32 (adapter, 0xffff0000, 0x02030000, 0, 4); // -> returns -1 </programlisting>
a #GstAdapter
mask to apply to data before matching against @pattern
pattern to match (after mask is applied)
offset into the adapter data from which to start scanning, returns the last scanned position.
number of bytes to scan from offset
Scan for pattern @pattern with applied mask @mask in the adapter data,
starting from offset @offset. If a match is found, the value that matched
is returned through @value, otherwise @value is left untouched.
The bytes in @pattern and @mask are interpreted left-to-right, regardless
of endianness. All four bytes of the pattern must be present in the
adapter for it to match, even if the first or last bytes are masked out.
It is an error to call this function without making sure that there is
enough data (offset+size bytes) in the adapter.
offset of the first match, or -1 if no match was found.
a #GstAdapter
mask to apply to data before matching against @pattern
pattern to match (after mask is applied)
offset into the adapter data from which to start scanning, returns the last scanned position.
number of bytes to scan from offset
pointer to uint32 to return matching data
Get the dts that was before the current byte in the adapter. When
@distance is given, the amount of bytes between the dts and the current
position is returned.
The dts is reset to GST_CLOCK_TIME_NONE and the distance is set to 0 when
the adapter is first created or when it is cleared. This also means that before
the first byte with a dts is removed from the adapter, the dts
and distance returned are GST_CLOCK_TIME_NONE and 0 respectively.
The previously seen dts.
a #GstAdapter
pointer to location for distance, or NULL
Get the pts that was before the current byte in the adapter. When
@distance is given, the amount of bytes between the pts and the current
position is returned.
The pts is reset to GST_CLOCK_TIME_NONE and the distance is set to 0 when
the adapter is first created or when it is cleared. This also means that before
the first byte with a pts is removed from the adapter, the pts
and distance returned are GST_CLOCK_TIME_NONE and 0 respectively.
The previously seen pts.
a #GstAdapter
pointer to location for distance, or NULL
Adds the data from @buf to the data stored inside @adapter and takes
ownership of the buffer.
a #GstAdapter
a #GstBuffer to add to queue in the adapter
Returns a freshly allocated buffer containing the first @nbytes bytes of the
@adapter. The returned bytes will be flushed from the adapter.
Caller owns returned value. g_free after usage.
Free-function: g_free
oven-fresh hot data, or #NULL if @nbytes bytes are not available
a #GstAdapter
the number of bytes to take
Returns a #GstBuffer containing the first @nbytes bytes of the
@adapter. The returned bytes will be flushed from the adapter.
This function is potentially more performant than gst_adapter_take()
since it can reuse the memory in pushed buffers by subbuffering
or merging.
Note that no assumptions should be made as to whether certain buffer
flags such as the DISCONT flag are set on the returned buffer, or not.
The caller needs to explicitly set or unset flags that should be set or
unset.
Caller owns a reference to the returned buffer. gst_buffer_unref() after
usage.
Free-function: gst_buffer_unref
a #GstBuffer containing the first @nbytes of the adapter, or #NULL if @nbytes bytes are not available. gst_buffer_unref() when no longer needed.
a #GstAdapter
the number of bytes to take
Returns a #GList of buffers containing the first @nbytes bytes of the
@adapter. The returned bytes will be flushed from the adapter.
When the caller can deal with individual buffers, this function is more
performant because no memory should be copied.
Caller owns returned list and contained buffers. gst_buffer_unref() each
buffer in the list before freeing the list after usage.
a #GList of buffers containing the first @nbytes of the adapter, or #NULL if @nbytes bytes are not available
a #GstAdapter
the number of bytes to take
Releases the memory obtained with the last gst_adapter_map().
a #GstAdapter
The name of the templates for the sink pad.
The name of the templates for the source pad.
This base class is for parser elements that process data and splits it
into separate audio/video/whatever frames.
It provides for:
<itemizedlist>
<listitem><para>provides one sink pad and one source pad</para></listitem>
<listitem><para>handles state changes</para></listitem>
<listitem><para>can operate in pull mode or push mode</para></listitem>
<listitem><para>handles seeking in both modes</para></listitem>
<listitem><para>handles events (SEGMENT/EOS/FLUSH)</para></listitem>
<listitem><para>
handles queries (POSITION/DURATION/SEEKING/FORMAT/CONVERT)
</para></listitem>
<listitem><para>handles flushing</para></listitem>
</itemizedlist>
The purpose of this base class is to provide the basic functionality of
a parser and share a lot of rather complex code.
Description of the parsing mechanism:
<orderedlist>
<listitem>
<itemizedlist><title>Set-up phase</title>
<listitem><para>
GstBaseParse calls @start to inform subclass that data processing is
about to start now.
</para></listitem>
<listitem><para>
GstBaseParse class calls @set_sink_caps to inform the subclass about
incoming sinkpad caps. Subclass could already set the srcpad caps
accordingly, but this might be delayed until calling
gst_base_parse_finish_frame() with a non-queued frame.
</para></listitem>
<listitem><para>
At least at this point subclass needs to tell the GstBaseParse class
how big data chunks it wants to receive (min_frame_size). It can do
this with gst_base_parse_set_min_frame_size().
</para></listitem>
<listitem><para>
GstBaseParse class sets up appropriate data passing mode (pull/push)
and starts to process the data.
</para></listitem>
</itemizedlist>
</listitem>
<listitem>
<itemizedlist>
<title>Parsing phase</title>
<listitem><para>
GstBaseParse gathers at least min_frame_size bytes of data either
by pulling it from upstream or collecting buffers in an internal
#GstAdapter.
</para></listitem>
<listitem><para>
A buffer of (at least) min_frame_size bytes is passed to subclass with
@handle_frame. Subclass checks the contents and can optionally
return GST_FLOW_OK along with an amount of data to be skipped to find
a valid frame (which will result in a subsequent DISCONT).
If, otherwise, the buffer does not hold a complete frame,
@handle_frame can merely return and will be called again when additional
data is available. In push mode this amounts to an
additional input buffer (thus minimal additional latency), in pull mode
this amounts to some arbitrary reasonable buffer size increase.
Of course, gst_base_parse_set_min_frame_size() could also be used if a
very specific known amount of additional data is required.
If, however, the buffer holds a complete valid frame, it can pass
the size of this frame to gst_base_parse_finish_frame().
If acting as a converter, it can also merely indicate consumed input data
while simultaneously providing custom output data.
Note that baseclass performs some processing (such as tracking
overall consumed data rate versus duration) for each finished frame,
but other state is only updated upon each call to @handle_frame
(such as tracking upstream input timestamp).
</para><para>
Subclass is also responsible for setting the buffer metadata
(e.g. buffer timestamp and duration, or keyframe if applicable).
(although the latter can also be done by GstBaseParse if it is
appropriately configured, see below). Frame is provided with
timestamp derived from upstream (as much as generally possible),
duration obtained from configuration (see below), and offset
if meaningful (in pull mode).
</para><para>
Note that @check_valid_frame might receive any small
amount of input data when leftover data is being drained (e.g. at EOS).
</para></listitem>
<listitem><para>
As part of finish frame processing,
just prior to actually pushing the buffer in question,
it is passed to @pre_push_frame which gives subclass yet one
last chance to examine buffer metadata, or to send some custom (tag)
events, or to perform custom (segment) filtering.
</para></listitem>
<listitem><para>
During the parsing process GstBaseParseClass will handle both srcpad
and sinkpad events. They will be passed to subclass if @event or
@src_event callbacks have been provided.
</para></listitem>
</itemizedlist>
</listitem>
<listitem>
<itemizedlist><title>Shutdown phase</title>
<listitem><para>
GstBaseParse class calls @stop to inform the subclass that data
parsing will be stopped.
</para></listitem>
</itemizedlist>
</listitem>
</orderedlist>
Subclass is responsible for providing pad template caps for
source and sink pads. The pads need to be named "sink" and "src". It also
needs to set the fixed caps on srcpad, when the format is ensured (e.g.
when base class calls subclass' @set_sink_caps function).
This base class uses #GST_FORMAT_DEFAULT as a meaning of frames. So,
subclass conversion routine needs to know that conversion from
#GST_FORMAT_TIME to #GST_FORMAT_DEFAULT must return the
frame number that can be found from the given byte position.
GstBaseParse uses subclasses conversion methods also for seeking (or
otherwise uses its own default one, see also below).
Subclass @start and @stop functions will be called to inform the beginning
and end of data processing.
Things that subclass need to take care of:
<itemizedlist>
<listitem><para>Provide pad templates</para></listitem>
<listitem><para>
Fixate the source pad caps when appropriate
</para></listitem>
<listitem><para>
Inform base class how big data chunks should be retrieved. This is
done with gst_base_parse_set_min_frame_size() function.
</para></listitem>
<listitem><para>
Examine data chunks passed to subclass with @handle_frame and pass
proper frame(s) to gst_base_parse_finish_frame(), and setting src pad
caps and timestamps on frame.
</para></listitem>
<listitem><para>Provide conversion functions</para></listitem>
<listitem><para>
Update the duration information with gst_base_parse_set_duration()
</para></listitem>
<listitem><para>
Optionally passthrough using gst_base_parse_set_passthrough()
</para></listitem>
<listitem><para>
Configure various baseparse parameters using
gst_base_parse_set_average_bitrate(), gst_base_parse_set_syncable()
and gst_base_parse_set_frame_rate().
</para></listitem>
<listitem><para>
In particular, if subclass is unable to determine a duration, but
parsing (or specs) yields a frames per seconds rate, then this can be
provided to GstBaseParse to enable it to cater for
buffer time metadata (which will be taken from upstream as much as
possible). Internally keeping track of frame durations and respective
sizes that have been pushed provides GstBaseParse with an estimated
bitrate. A default @convert (used if not overriden) will then use these
rates to perform obvious conversions. These rates are also used to
update (estimated) duration at regular frame intervals.
</para></listitem>
</itemizedlist>
Adds an entry to the index associating @offset to @ts. It is recommended
to only add keyframe entries. @force allows to bypass checks, such as
whether the stream is (upstream) seekable, another entry is already "close"
to the new entry, etc.
#gboolean indicating whether entry was added
#GstBaseParse.
offset of entry
timestamp associated with offset
whether entry refers to keyframe
add entry disregarding sanity checks
Default implementation of "convert" vmethod in #GstBaseParse class.
TRUE if conversion was successful.
#GstBaseParse.
#GstFormat describing the source format.
Source value to be converted.
#GstFormat defining the converted format.
Pointer where the conversion result will be put.
Collects parsed data and pushes this downstream.
Source pad caps must be set when this is called.
If @frame's out_buffer is set, that will be used as subsequent frame data.
Otherwise, @size samples will be taken from the input and used for output,
and the output's metadata (timestamps etc) will be taken as (optionally)
set by the subclass on @frame's (input) buffer (which is otherwise
ignored for any but the above purpose/information).
Note that the latter buffer is invalidated by this call, whereas the
caller retains ownership of @frame.
a #GstFlowReturn that should be escalated to caller (of caller)
a #GstBaseParse
a #GstBaseParseFrame
consumed input data represented by frame
Pushes the frame's buffer downstream, sends any pending events and
does some timestamp and segment handling. Takes ownership of
frame's buffer, though caller retains ownership of @frame.
This must be called with sinkpad STREAM_LOCK held.
#GstFlowReturn
#GstBaseParse.
a #GstBaseParseFrame
Optionally sets the average bitrate detected in media (if non-zero),
e.g. based on metadata, as it will be posted to the application.
By default, announced average bitrate is estimated. The average bitrate
is used to estimate the total duration of the stream and to estimate
a seek position, if there's no index and the format is syncable
(see gst_base_parse_set_syncable()).
#GstBaseParse.
average bitrate in bits/second
Sets the duration of the currently playing media. Subclass can use this
when it is able to determine duration and/or notices a change in the media
duration. Alternatively, if @interval is non-zero (default), then stream
duration is determined based on estimated bitrate, and updated every @interval
frames.
#GstBaseParse.
#GstFormat.
duration value.
how often to update the duration estimate based on bitrate, or 0.
If frames per second is configured, parser can take care of buffer duration
and timestamping. When performing segment clipping, or seeking to a specific
location, a corresponding decoder might need an initial @lead_in and a
following @lead_out number of frames to ensure the desired segment is
entirely filled upon decoding.
the #GstBaseParse to set
frames per second (numerator).
frames per second (denominator).
frames needed before a segment for subsequent decode
frames needed after a segment
Set if frames carry timing information which the subclass can (generally)
parse and provide. In particular, intrinsic (rather than estimated) time
can be obtained following a seek.
a #GstBaseParse
whether frames carry timing information
Sets the minimum and maximum (which may likely be equal) latency introduced
by the parsing process. If there is such a latency, which depends on the
particular parsing of the format, it typically corresponds to 1 frame duration.
a #GstBaseParse
minimum parse latency
maximum parse latency
Subclass can use this function to tell the base class that it needs to
give at least #min_size buffers.
#GstBaseParse.
Minimum size of the data that this base class should give to subclass.
Set if the nature of the format or configuration does not allow (much)
parsing, and the parser should operate in passthrough mode (which only
applies when operating in push mode). That is, incoming buffers are
pushed through unmodified, i.e. no @check_valid_frame or @parse_frame
callbacks will be invoked, but @pre_push_frame will still be invoked,
so subclass can perform as much or as little is appropriate for
passthrough semantics in @pre_push_frame.
a #GstBaseParse
%TRUE if parser should run in passthrough mode
By default, the base class will guess PTS timestamps using a simple
interpolation (previous timestamp + duration), which is incorrect for
data streams with reordering, where PTS can go backward. Sub-classes
implementing such formats should disable PTS interpolation.
a #GstBaseParse
%TRUE if parser should interpolate PTS timestamps
Set if frame starts can be identified. This is set by default and
determines whether seeking based on bitrate averages
is possible for a format/stream.
a #GstBaseParse
set if frame starts can be identified
Subclasses can override any of the available virtual methods or not, as
needed. At minimum @check_valid_frame and @parse_frame needs to be
overridden.
Frame (context) data passed to each frame parsing virtual methods. In
addition to providing the data to be checked for a valid frame or an already
identified frame, it conveys additional metadata or control information
from and to the subclass w.r.t. the particular frame in question (rather
than global parameters). Some of these may apply to each parsing stage, others
only to some a particular one. These parameters are effectively zeroed at start
of each frame's processing, i.e. parsing virtual method invocation sequence.
Allocates a new #GstBaseParseFrame. This function is mainly for bindings,
elements written in C should usually allocate the frame on the stack and
then use gst_base_parse_frame_init() to initialise it.
a newly-allocated #GstBaseParseFrame. Free with gst_base_parse_frame_free() when no longer needed.
a #GstBuffer
the flags
number of bytes in this frame which should be counted as metadata overhead, ie. not used to calculate the average bitrate. Set to -1 to mark the entire frame as metadata. If in doubt, set to 0.
Sets a #GstBaseParseFrame to initial state. Currently this means
all public fields are zero-ed and a private flag is set to make
sure gst_base_parse_frame_free() only frees the contents but not
the actual frame. Use this function to initialise a #GstBaseParseFrame
allocated on the stack.
#GstBaseParseFrame.
Flags to be used in a #GstBaseParseFrame.
no flag
set by baseclass if current frame is passed for processing to the subclass for the first time (and not set on subsequent calls with same data).
set to indicate this buffer should not be counted as frame, e.g. if this frame is dependent on a previous one. As it is not counted as a frame, bitrate increases but frame to time conversions are maintained.
@pre_push_frame can set this to indicate that regular segment clipping can still be performed (as opposed to any custom one having been done).
indicates to @finish_frame that the the frame should be dropped (and might be handled internall by subclass)
indicates to @finish_frame that the the frame should be queued for now and processed fully later when the first non-queued frame is finished
#GstBaseSink is the base class for sink elements in GStreamer, such as
xvimagesink or filesink. It is a layer on top of #GstElement that provides a
simplified interface to plugin writers. #GstBaseSink handles many details
for you, for example: preroll, clock synchronization, state changes,
activation in push or pull mode, and queries.
In most cases, when writing sink elements, there is no need to implement
class methods from #GstElement or to set functions on pads, because the
#GstBaseSink infrastructure should be sufficient.
#GstBaseSink provides support for exactly one sink pad, which should be
named "sink". A sink implementation (subclass of #GstBaseSink) should
install a pad template in its class_init function, like so:
|[
static void
my_element_class_init (GstMyElementClass *klass)
{
GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
// sinktemplate should be a #GstStaticPadTemplate with direction
// #GST_PAD_SINK and name "sink"
gst_element_class_add_pad_template (gstelement_class,
gst_static_pad_template_get (&sinktemplate));
gst_element_class_set_static_metadata (gstelement_class,
"Sink name",
"Sink",
"My Sink element",
"The author <my.sink@my.email>");
}
]|
#GstBaseSink will handle the prerolling correctly. This means that it will
return #GST_STATE_CHANGE_ASYNC from a state change to PAUSED until the first
buffer arrives in this element. The base class will call the
#GstBaseSinkClass.preroll() vmethod with this preroll buffer and will then
commit the state change to the next asynchronously pending state.
When the element is set to PLAYING, #GstBaseSink will synchronise on the
clock using the times returned from #GstBaseSinkClass.get_times(). If this
function returns #GST_CLOCK_TIME_NONE for the start time, no synchronisation
will be done. Synchronisation can be disabled entirely by setting the object
#GstBaseSink:sync property to %FALSE.
After synchronisation the virtual method #GstBaseSinkClass.render() will be
called. Subclasses should minimally implement this method.
Subclasses that synchronise on the clock in the #GstBaseSinkClass.render()
method are supported as well. These classes typically receive a buffer in
the render method and can then potentially block on the clock while
rendering. A typical example is an audiosink.
These subclasses can use gst_base_sink_wait_preroll() to perform the
blocking wait.
Upon receiving the EOS event in the PLAYING state, #GstBaseSink will wait
for the clock to reach the time indicated by the stop time of the last
#GstBaseSinkClass.get_times() call before posting an EOS message. When the
element receives EOS in PAUSED, preroll completes, the event is queued and an
EOS message is posted when going to PLAYING.
#GstBaseSink will internally use the #GST_EVENT_SEGMENT events to schedule
synchronisation and clipping of buffers. Buffers that fall completely outside
of the current segment are dropped. Buffers that fall partially in the
segment are rendered (and prerolled). Subclasses should do any subbuffer
clipping themselves when needed.
#GstBaseSink will by default report the current playback position in
#GST_FORMAT_TIME based on the current clock time and segment information.
If no clock has been set on the element, the query will be forwarded
upstream.
The #GstBaseSinkClass.set_caps() function will be called when the subclass
should configure itself to process a specific media type.
The #GstBaseSinkClass.start() and #GstBaseSinkClass.stop() virtual methods
will be called when resources should be allocated. Any
#GstBaseSinkClass.preroll(), #GstBaseSinkClass.render() and
#GstBaseSinkClass.set_caps() function will be called between the
#GstBaseSinkClass.start() and #GstBaseSinkClass.stop() calls.
The #GstBaseSinkClass.event() virtual method will be called when an event is
received by #GstBaseSink. Normally this method should only be overriden by
very specific elements (such as file sinks) which need to handle the
newsegment event specially.
The #GstBaseSinkClass.unlock() method is called when the elements should
unblock any blocking operations they perform in the
#GstBaseSinkClass.render() method. This is mostly useful when the
#GstBaseSinkClass.render() method performs a blocking write on a file
descriptor, for example.
The #GstBaseSink:max-lateness property affects how the sink deals with
buffers that arrive too late in the sink. A buffer arrives too late in the
sink when the presentation time (as a combination of the last segment, buffer
timestamp and element base_time) plus the duration is before the current
time of the clock.
If the frame is later than max-lateness, the sink will drop the buffer
without calling the render method.
This feature is disabled if sync is disabled, the
#GstBaseSinkClass.get_times() method does not return a valid start time or
max-lateness is set to -1 (the default).
Subclasses can use gst_base_sink_set_max_lateness() to configure the
max-lateness value.
The #GstBaseSink:qos property will enable the quality-of-service features of
the basesink which gather statistics about the real-time performance of the
clock synchronisation. For each buffer received in the sink, statistics are
gathered and a QOS event is sent upstream with these numbers. This
information can then be used by upstream elements to reduce their processing
rate, for example.
The #GstBaseSink:async property can be used to instruct the sink to never
perform an ASYNC state change. This feature is mostly usable when dealing
with non-synchronized streams or sparse streams.
Last reviewed on 2007-08-29 (0.10.15)
If the @sink spawns its own thread for pulling buffers from upstream it
should call this method after it has pulled a buffer. If the element needed
to preroll, this function will perform the preroll and will then block
until the element state is changed.
This function should be called with the PREROLL_LOCK held.
#GST_FLOW_OK if the preroll completed and processing can continue. Any other return value should be returned from the render vmethod.
the sink
the mini object that caused the preroll
Get the number of bytes that the sink will pull when it is operating in pull
mode.
the number of bytes @sink will pull in pull mode.
a #GstBaseSink
Get the last sample that arrived in the sink and was used for preroll or for
rendering. This property can be used to generate thumbnails.
The #GstCaps on the sample can be used to determine the type of the buffer.
Free-function: gst_sample_unref
a #GstSample. gst_sample_unref() after usage. This function returns NULL when no buffer has arrived in the sink yet or when the sink is not in PAUSED or PLAYING.
the sink
Get the currently configured latency.
The configured latency.
the sink
Gets the max lateness value. See gst_base_sink_set_max_lateness for
more details.
The maximum time in nanoseconds that a buffer can be late before it is dropped and not rendered. A value of -1 means an unlimited time.
the sink
Get the render delay of @sink. see gst_base_sink_set_render_delay() for more
information about the render delay.
the render delay of @sink.
a #GstBaseSink
Checks if @sink is currently configured to synchronize against the
clock.
TRUE if the sink is configured to synchronize against the clock.
the sink
Get the time that will be inserted between frames to control the
maximum buffers per second.
the number of nanoseconds @sink will put between frames.
a #GstBaseSink
Get the synchronisation offset of @sink.
The synchronisation offset.
the sink
Checks if @sink is currently configured to perform asynchronous state
changes to PAUSED.
TRUE if the sink is configured to perform asynchronous state changes.
the sink
Checks if @sink is currently configured to store the last received sample in
the last-sample property.
TRUE if the sink is configured to store the last received sample.
the sink
Checks if @sink is currently configured to send Quality-of-Service events
upstream.
TRUE if the sink is configured to perform Quality-of-Service.
the sink
Query the sink for the latency parameters. The latency will be queried from
the upstream elements. @live will be TRUE if @sink is configured to
synchronize against the clock. @upstream_live will be TRUE if an upstream
element is live.
If both @live and @upstream_live are TRUE, the sink will want to compensate
for the latency introduced by the upstream elements by setting the
@min_latency to a strictly possitive value.
This function is mostly used by subclasses.
TRUE if the query succeeded.
the sink
if the sink is live
if an upstream element is live
the min latency of the upstream elements
the max latency of the upstream elements
Configures @sink to perform all state changes asynchronusly. When async is
disabled, the sink will immediately go to PAUSED instead of waiting for a
preroll buffer. This feature is useful if the sink does not synchronize
against the clock or when it is dealing with sparse streams.
the sink
the new async value.
Set the number of bytes that the sink will pull when it is operating in pull
mode.
a #GstBaseSink
the blocksize in bytes
Configures @sink to store the last received sample in the last-sample
property.
the sink
the new enable-last-sample value.
Sets the new max lateness value to @max_lateness. This value is
used to decide if a buffer should be dropped or not based on the
buffer timestamp and the current clock time. A value of -1 means
an unlimited time.
the sink
the new max lateness value.
Configures @sink to send Quality-of-Service events upstream.
the sink
the new qos value.
Set the render delay in @sink to @delay. The render delay is the time
between actual rendering of a buffer and its synchronisation time. Some
devices might delay media rendering which can be compensated for with this
function.
After calling this function, this sink will report additional latency and
other sinks will adjust their latency to delay the rendering of their media.
This function is usually called by subclasses.
a #GstBaseSink
the new delay
Configures @sink to synchronize on the clock or not. When
@sync is FALSE, incoming samples will be played as fast as
possible. If @sync is TRUE, the timestamps of the incomming
buffers will be used to schedule the exact render time of its
contents.
the sink
the new sync value.
Set the time that will be inserted between rendered buffers. This
can be used to control the maximum buffers per second that the sink
will render.
a #GstBaseSink
the throttle time in nanoseconds
Adjust the synchronisation of @sink with @offset. A negative value will
render buffers earlier than their timestamp. A positive value will delay
rendering. This function can be used to fix playback of badly timestamped
buffers.
the sink
the new offset
This function will wait for preroll to complete and will then block until @time
is reached. It is usually called by subclasses that use their own internal
synchronisation but want to let some synchronization (like EOS) be handled
by the base class.
This function should only be called with the PREROLL_LOCK held (like when
receiving an EOS event in the ::event vmethod or when handling buffers in
::render).
The @time argument should be the running_time of when the timeout should happen
and will be adjusted with any latency and offset configured in the sink.
#GstFlowReturn
the sink
the running_time to be reached
the jitter to be filled with time diff, or NULL
This function will block until @time is reached. It is usually called by
subclasses that use their own internal synchronisation.
If @time is not valid, no sycnhronisation is done and #GST_CLOCK_BADTIME is
returned. Likewise, if synchronisation is disabled in the element or there
is no clock, no synchronisation is done and #GST_CLOCK_BADTIME is returned.
This function should only be called with the PREROLL_LOCK held, like when
receiving an EOS event in the #GstBaseSinkClass.event() vmethod or when
receiving a buffer in
the #GstBaseSinkClass.render() vmethod.
The @time argument should be the running_time of when this method should
return and is not adjusted with any latency or offset configured in the
sink.
#GstClockReturn
the sink
the running_time to be reached
the jitter to be filled with time diff, or NULL
If the #GstBaseSinkClass.render() method performs its own synchronisation
against the clock it must unblock when going from PLAYING to the PAUSED state
and call this method before continuing to render the remaining data.
This function will block until a state change to PLAYING happens (in which
case this function returns #GST_FLOW_OK) or the processing must be stopped due
to a state change to READY or a FLUSH event (in which case this function
returns #GST_FLOW_FLUSHING).
This function should only be called with the PREROLL_LOCK held, like in the
render function.
#GST_FLOW_OK if the preroll completed and processing can continue. Any other return value should be returned from the render vmethod.
the sink
If set to #TRUE, the basesink will perform asynchronous state changes.
When set to #FALSE, the sink will not signal the parent when it prerolls.
Use this option when dealing with sparse streams or when synchronisation is
not required.
The amount of bytes to pull when operating in pull mode.
Enable the last-sample property. If FALSE, basesink doesn't keep a
reference to the last buffer arrived and the last-sample property is always
set to NULL. This can be useful if you need buffers to be released as soon
as possible, eg. if you're using a buffer pool.
The last buffer that arrived in the sink and was used for preroll or for
rendering. This property can be used to generate thumbnails. This property
can be NULL when the sink has not yet received a bufer.
The additional delay between synchronisation and actual rendering of the
media. This property will add additional latency to the device in order to
make other sinks compensate for the delay.
The time to insert between buffers. This property can be used to control
the maximum amount of buffers per second to render. Setting this property
to a value bigger than 0 will make the sink create THROTTLE QoS events.
Controls the final synchronisation, a negative value will render the buffer
earlier while a positive value delays playback. This property can be
used to fix synchronisation in bad files.
Subclasses can override any of the available virtual methods or not, as
needed. At the minimum, the @render method should be overridden to
output/present buffers.
This is a generice base class for source elements. The following
types of sources are supported:
<itemizedlist>
<listitem><para>random access sources like files</para></listitem>
<listitem><para>seekable sources</para></listitem>
<listitem><para>live sources</para></listitem>
</itemizedlist>
The source can be configured to operate in any #GstFormat with the
gst_base_src_set_format() method. The currently set format determines
the format of the internal #GstSegment and any #GST_EVENT_SEGMENT
events. The default format for #GstBaseSrc is #GST_FORMAT_BYTES.
#GstBaseSrc always supports push mode scheduling. If the following
conditions are met, it also supports pull mode scheduling:
<itemizedlist>
<listitem><para>The format is set to #GST_FORMAT_BYTES (default).</para>
</listitem>
<listitem><para>#GstBaseSrcClass.is_seekable() returns %TRUE.</para>
</listitem>
</itemizedlist>
If all the conditions are met for operating in pull mode, #GstBaseSrc is
automatically seekable in push mode as well. The following conditions must
be met to make the element seekable in push mode when the format is not
#GST_FORMAT_BYTES:
<itemizedlist>
<listitem><para>
#GstBaseSrcClass.is_seekable() returns %TRUE.
</para></listitem>
<listitem><para>
#GstBaseSrcClass.query() can convert all supported seek formats to the
internal format as set with gst_base_src_set_format().
</para></listitem>
<listitem><para>
#GstBaseSrcClass.do_seek() is implemented, performs the seek and returns
%TRUE.
</para></listitem>
</itemizedlist>
When the element does not meet the requirements to operate in pull mode, the
offset and length in the #GstBaseSrcClass.create() method should be ignored.
It is recommended to subclass #GstPushSrc instead, in this situation. If the
element can operate in pull mode but only with specific offsets and
lengths, it is allowed to generate an error when the wrong values are passed
to the #GstBaseSrcClass.create() function.
#GstBaseSrc has support for live sources. Live sources are sources that when
paused discard data, such as audio or video capture devices. A typical live
source also produces data at a fixed rate and thus provides a clock to publish
this rate.
Use gst_base_src_set_live() to activate the live source mode.
A live source does not produce data in the PAUSED state. This means that the
#GstBaseSrcClass.create() method will not be called in PAUSED but only in
PLAYING. To signal the pipeline that the element will not produce data, the
return value from the READY to PAUSED state will be
#GST_STATE_CHANGE_NO_PREROLL.
A typical live source will timestamp the buffers it creates with the
current running time of the pipeline. This is one reason why a live source
can only produce data in the PLAYING state, when the clock is actually
distributed and running.
Live sources that synchronize and block on the clock (an audio source, for
example) can use gst_base_src_wait_playing() when the
#GstBaseSrcClass.create() function was interrupted by a state change to
PAUSED.
The #GstBaseSrcClass.get_times() method can be used to implement pseudo-live
sources. It only makes sense to implement the #GstBaseSrcClass.get_times()
function if the source is a live source. The #GstBaseSrcClass.get_times()
function should return timestamps starting from 0, as if it were a non-live
source. The base class will make sure that the timestamps are transformed
into the current running_time. The base source will then wait for the
calculated running_time before pushing out the buffer.
For live sources, the base class will by default report a latency of 0.
For pseudo live sources, the base class will by default measure the difference
between the first buffer timestamp and the start time of get_times and will
report this value as the latency.
Subclasses should override the query function when this behaviour is not
acceptable.
There is only support in #GstBaseSrc for exactly one source pad, which
should be named "src". A source implementation (subclass of #GstBaseSrc)
should install a pad template in its class_init function, like so:
|[
static void
my_element_class_init (GstMyElementClass *klass)
{
GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
// srctemplate should be a #GstStaticPadTemplate with direction
// #GST_PAD_SRC and name "src"
gst_element_class_add_pad_template (gstelement_class,
gst_static_pad_template_get (&srctemplate));
gst_element_class_set_static_metadata (gstelement_class,
"Source name",
"Source",
"My Source element",
"The author <my.sink@my.email>");
}
]|
<refsect2>
<title>Controlled shutdown of live sources in applications</title>
<para>
Applications that record from a live source may want to stop recording
in a controlled way, so that the recording is stopped, but the data
already in the pipeline is processed to the end (remember that many live
sources would go on recording forever otherwise). For that to happen the
application needs to make the source stop recording and send an EOS
event down the pipeline. The application would then wait for an
EOS message posted on the pipeline's bus to know when all data has
been processed and the pipeline can safely be stopped.
An application may send an EOS event to a source element to make it
perform the EOS logic (send EOS event downstream or post a
#GST_MESSAGE_SEGMENT_DONE on the bus). This can typically be done
with the gst_element_send_event() function on the element or its parent bin.
After the EOS has been sent to the element, the application should wait for
an EOS message to be posted on the pipeline's bus. Once this EOS message is
received, it may safely shut down the entire pipeline.
Last reviewed on 2007-12-19 (0.10.16)
</para>
</refsect2>
Set new caps on the basesrc source pad.
%TRUE if the caps could be set
a #GstCaps
Lets #GstBaseSrc sub-classes to know the memory @allocator
used by the base class and its @params.
Unref the @allocator after use it.
a #GstBaseSrc
the #GstAllocator used
the #GstAllocatorParams of @allocator
Get the number of bytes that @src will push out with each buffer.
the number of bytes pushed with each buffer.
the source
the instance of the #GstBufferPool used by the src; free it after use it
a #GstBaseSrc
Query if @src timestamps outgoing buffers based on the current running_time.
%TRUE if the base class will automatically timestamp outgoing buffers.
the source
Get the current async behaviour of @src. See also gst_base_src_set_async().
%TRUE if @src is operating in async mode.
base source instance
Check if an element is in live mode.
%TRUE if element is in live mode.
base source instance
Prepare a new seamless segment for emission downstream. This function must
only be called by derived sub-classes, and only from the create() function,
as the stream-lock needs to be held.
The format for the new segment will be the current format of the source, as
configured with gst_base_src_set_format()
%TRUE if preparation of the seamless segment succeeded.
The source
The new start value for the segment
Stop value for the new segment
The new time value for the start of the new segent
Query the source for the latency parameters. @live will be TRUE when @src is
configured as a live source. @min_latency will be set to the difference
between the running time and the timestamp of the first buffer.
@max_latency is always the undefined value of -1.
This function is mostly used by subclasses.
TRUE if the query succeeded.
the source
if the source is live
the min latency of the source
the max latency of the source
Configure async behaviour in @src, no state change will block. The open,
close, start, stop, play and pause virtual methods will be executed in a
different thread and are thus allowed to perform blocking operations. Any
blocking operation should be unblocked with the unlock vmethod.
base source instance
new async mode
Set the number of bytes that @src will push out with each buffer. When
@blocksize is set to -1, a default length will be used.
the source
the new blocksize in bytes
Set new caps on the basesrc source pad.
%TRUE if the caps could be set
a #GstBaseSrc
a #GstCaps
Configure @src to automatically timestamp outgoing buffers based on the
current running_time of the pipeline. This property is mostly useful for live
sources.
the source
enable or disable timestamping
If not @dynamic, size is only updated when needed, such as when trying to
read past current tracked size. Otherwise, size is checked for upon each
read.
base source instance
new dynamic size mode
Sets the default format of the source. This will be the format used
for sending SEGMENT events and for performing seeks.
If a format of GST_FORMAT_BYTES is set, the element will be able to
operate in pull mode if the #GstBaseSrcClass.is_seekable() returns TRUE.
This function must only be called in states < %GST_STATE_PAUSED.
base source instance
the format to use
If the element listens to a live source, @live should
be set to %TRUE.
A live source will not produce data in the PAUSED state and
will therefore not be able to participate in the PREROLL phase
of a pipeline. To signal this fact to the application and the
pipeline, the state change return value of the live source will
be GST_STATE_CHANGE_NO_PREROLL.
base source instance
new live-mode
Complete an asynchronous start operation. When the subclass overrides the
start method, it should call gst_base_src_start_complete() when the start
operation completes either from the same thread or from an asynchronous
helper thread.
base source instance
a #GstFlowReturn
Wait until the start operation completes.
a #GstFlowReturn.
base source instance
If the #GstBaseSrcClass.create() method performs its own synchronisation
against the clock it must unblock when going from PLAYING to the PAUSED state
and call this method before continuing to produce the remaining data.
This function will block until a state change to PLAYING happens (in which
case this function returns #GST_FLOW_OK) or the processing must be stopped due
to a state change to READY or a FLUSH event (in which case this function
returns #GST_FLOW_FLUSHING).
#GST_FLOW_OK if @src is PLAYING and processing can continue. Any other return value should be returned from the create vmethod.
the src
Subclasses can override any of the available virtual methods or not, as
needed. At the minimum, the @create method should be overridden to produce
buffers.
%TRUE if the caps could be set
a #GstCaps
The #GstElement flags that a basesrc element may have.
has source is starting
has source been started
offset to define more flags
This base class is for filter elements that process data.
It provides for:
<itemizedlist>
<listitem><para>one sinkpad and one srcpad</para></listitem>
<listitem><para>
Possible formats on sink and source pad implemented
with custom transform_caps function. By default uses
same format on sink and source.
</para></listitem>
<listitem><para>Handles state changes</para></listitem>
<listitem><para>Does flushing</para></listitem>
<listitem><para>Push mode</para></listitem>
<listitem><para>
Pull mode if the sub-class transform can operate on arbitrary data
</para></listitem>
</itemizedlist>
<refsect2>
<title>Use Cases</title>
<para>
<orderedlist>
<listitem>
<itemizedlist><title>Passthrough mode</title>
<listitem><para>
Element has no interest in modifying the buffer. It may want to inspect it,
in which case the element should have a transform_ip function. If there
is no transform_ip function in passthrough mode, the buffer is pushed
intact.
</para></listitem>
<listitem><para>
On the GstBaseTransformClass is the passthrough_on_same_caps variable
which will automatically set/unset passthrough based on whether the
element negotiates the same caps on both pads.
</para></listitem>
<listitem><para>
passthrough_on_same_caps on an element that doesn't implement a
transform_caps function is useful for elements that only inspect data
(such as level)
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Example elements</title>
<listitem>Level</listitem>
<listitem>Videoscale, audioconvert, videoconvert, audioresample in
certain modes.</listitem>
</itemizedlist>
</listitem>
<listitem>
<itemizedlist>
<title>Modifications in-place - input buffer and output buffer are the
same thing.</title>
<listitem><para>
The element must implement a transform_ip function.
</para></listitem>
<listitem><para>
Output buffer size must <= input buffer size
</para></listitem>
<listitem><para>
If the always_in_place flag is set, non-writable buffers will be copied
and passed to the transform_ip function, otherwise a new buffer will be
created and the transform function called.
</para></listitem>
<listitem><para>
Incoming writable buffers will be passed to the transform_ip function
immediately. </para></listitem>
<listitem><para>
only implementing transform_ip and not transform implies always_in_place
= TRUE
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Example elements</title>
<listitem>Volume</listitem>
<listitem>Audioconvert in certain modes (signed/unsigned
conversion)</listitem>
<listitem>videoconvert in certain modes (endianness
swapping)</listitem>
</itemizedlist>
</listitem>
<listitem>
<itemizedlist>
<title>Modifications only to the caps/metadata of a buffer</title>
<listitem><para>
The element does not require writable data, but non-writable buffers
should be subbuffered so that the meta-information can be replaced.
</para></listitem>
<listitem><para>
Elements wishing to operate in this mode should replace the
prepare_output_buffer method to create subbuffers of the input buffer
and set always_in_place to TRUE
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Example elements</title>
<listitem>Capsfilter when setting caps on outgoing buffers that have
none.</listitem>
<listitem>identity when it is going to re-timestamp buffers by
datarate.</listitem>
</itemizedlist>
</listitem>
<listitem>
<itemizedlist><title>Normal mode</title>
<listitem><para>
always_in_place flag is not set, or there is no transform_ip function
</para></listitem>
<listitem><para>
Element will receive an input buffer and output buffer to operate on.
</para></listitem>
<listitem><para>
Output buffer is allocated by calling the prepare_output_buffer function.
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Example elements</title>
<listitem>Videoscale, videoconvert, audioconvert when doing
scaling/conversions</listitem>
</itemizedlist>
</listitem>
<listitem>
<itemizedlist><title>Special output buffer allocations</title>
<listitem><para>
Elements which need to do special allocation of their output buffers
other than what gst_buffer_pad_alloc allows should implement a
prepare_output_buffer method, which calls the parent implementation and
passes the newly allocated buffer.
</para></listitem>
</itemizedlist>
<itemizedlist>
<title>Example elements</title>
<listitem>efence</listitem>
</itemizedlist>
</listitem>
</orderedlist>
</para>
</refsect2>
<refsect2>
<title>Sub-class settable flags on GstBaseTransform</title>
<para>
<itemizedlist>
<listitem><para>
<itemizedlist><title>passthrough</title>
<listitem><para>
Implies that in the current configuration, the sub-class is not
interested in modifying the buffers.
</para></listitem>
<listitem><para>
Elements which are always in passthrough mode whenever the same caps
has been negotiated on both pads can set the class variable
passthrough_on_same_caps to have this behaviour automatically.
</para></listitem>
</itemizedlist>
</para></listitem>
<listitem><para>
<itemizedlist><title>always_in_place</title>
<listitem><para>
Determines whether a non-writable buffer will be copied before passing
to the transform_ip function.
</para></listitem>
<listitem><para>
Implied TRUE if no transform function is implemented.
</para></listitem>
<listitem><para>
Implied FALSE if ONLY transform function is implemented.
</para></listitem>
</itemizedlist>
</para></listitem>
</itemizedlist>
</para>
</refsect2>
Lets #GstBaseTransform sub-classes to know the memory @allocator
used by the base class and its @params.
Unref the @allocator after use it.
a #GstBaseTransform
the #GstAllocator used
the #GstAllocatorParams of @allocator
the instance of the #GstBufferPool used by @trans; free it after use it
a #GstBaseTransform
See if @trans is configured as a in_place transform.
TRUE is the transform is configured in in_place mode. MT safe.
the #GstBaseTransform to query
See if @trans is configured as a passthrough transform.
TRUE is the transform is configured in passthrough mode. MT safe.
the #GstBaseTransform to query
Queries if the transform will handle QoS.
TRUE if QoS is enabled. MT safe.
a #GstBaseTransform
Instructs @trans to request renegotiation upstream. This function is
typically called after properties on the transform were set that
influence the input format.
a #GstBaseTransform
Instructs @trans to renegotiate a new downstream transform on the next
buffer. This function is typically called after properties on the transform
were set that influence the output format.
a #GstBaseTransform
If @gap_aware is %FALSE (the default), output buffers will have the
%GST_BUFFER_FLAG_GAP flag unset.
If set to %TRUE, the element must handle output buffers with this flag set
correctly, i.e. it can assume that the buffer contains neutral data but must
unset the flag if the output is no neutral data.
MT safe.
a #GstBaseTransform
New state
Determines whether a non-writable buffer will be copied before passing
to the transform_ip function.
<itemizedlist>
<listitem>Always TRUE if no transform function is implemented.</listitem>
<listitem>Always FALSE if ONLY transform function is implemented.</listitem>
</itemizedlist>
MT safe.
the #GstBaseTransform to modify
Boolean value indicating that we would like to operate on in_place buffers.
Set passthrough mode for this filter by default. This is mostly
useful for filters that do not care about negotiation.
Always TRUE for filters which don't implement either a transform
or transform_ip method.
MT safe.
the #GstBaseTransform to set
boolean indicating passthrough mode.
If @prefer_passthrough is %TRUE (the default), @trans will check and
prefer passthrough caps from the list of caps returned by the
transform_caps vmethod.
If set to %FALSE, the element must order the caps returned from the
transform_caps function in such a way that the prefered format is
first in the list. This can be interesting for transforms that can do
passthrough transforms but prefer to do something else, like a
capsfilter.
MT safe.
a #GstBaseTransform
New state
Enable or disable QoS handling in the transform.
MT safe.
a #GstBaseTransform
new state
Set the QoS parameters in the transform. This function is called internally
when a QOS event is received but subclasses can provide custom information
when needed.
MT safe.
a #GstBaseTransform
the proportion
the diff against the clock
the timestamp of the buffer generating the QoS expressed in running_time.
Subclasses can override any of the available virtual methods or not, as
needed. At minimum either @transform or @transform_ip need to be overridden.
If the element can overwrite the input data with the results (data is of the
same type and quantity) it should provide @transform_ip.
#GstBitReader provides a bit reader that can read any number of bits
from a memory buffer. It provides functions for reading any number of bits
into 8, 16, 32 and 64 bit variables.
Frees a #GstBitReader instance, which was previously allocated by
gst_bit_reader_new().
a #GstBitReader instance
Read @nbits bits into @val and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint16 to store the result
number of bits to read
Read @nbits bits into @val and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint32 to store the result
number of bits to read
Read @nbits bits into @val and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint64 to store the result
number of bits to read
Read @nbits bits into @val and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint8 to store the result
number of bits to read
Returns the current position of a #GstBitReader instance in bits.
The current position of @reader in bits.
a #GstBitReader instance
Returns the remaining number of bits of a #GstBitReader instance.
The remaining number of bits of @reader instance.
a #GstBitReader instance
Returns the total number of bits of a #GstBitReader instance.
The total number of bits of @reader instance.
a #GstBitReader instance
Initializes a #GstBitReader instance to read from @data. This function
can be called on already initialized instances.
a #GstBitReader instance
data from which the bit reader should read
Size of @data in bytes
Read @nbits bits into @val but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint16 to store the result
number of bits to read
Read @nbits bits into @val but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint32 to store the result
number of bits to read
Read @nbits bits into @val but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint64 to store the result
number of bits to read
Read @nbits bits into @val but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Pointer to a #guint8 to store the result
number of bits to read
Sets the new position of a #GstBitReader instance to @pos in bits.
%TRUE if the position could be set successfully, %FALSE otherwise.
a #GstBitReader instance
The new position in bits
Skips @nbits bits of the #GstBitReader instance.
%TRUE if @nbits bits could be skipped, %FALSE otherwise.
a #GstBitReader instance
the number of bits to skip
Skips until the next byte.
%TRUE if successful, %FALSE otherwise.
a #GstBitReader instance
Create a new #GstBitReader instance, which will read from @data.
Free-function: gst_bit_reader_free
a new #GstBitReader instance
Data from which the #GstBitReader should read
Size of @data in bytes
#GstByteReader provides a byte reader that can read different integer and
floating point types from a memory buffer. It provides functions for reading
signed/unsigned, little/big endian integers of 8, 16, 24, 32 and 64 bits
and functions for reading little/big endian floating points numbers of
32 and 64 bits. It also provides functions to read NUL-terminated strings
in various character encodings.
Free-function: g_free
Returns a newly-allocated copy of the current data
position if at least @size bytes are left and
updates the current position. Free with g_free() when no longer needed.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Size in bytes
address of a #guint8 pointer variable in which to store the result
Free-function: g_free
Returns a newly-allocated copy of the current data position if there is
a NUL-terminated UTF-16 string in the data (this could be an empty string
as well), and advances the current position.
No input checking for valid UTF-16 is done. This function is endianness
agnostic - you should not assume the UTF-16 characters are in host
endianness.
This function will fail if no NUL-terminator was found in in the data.
Note: there is no peek or get variant of this function to ensure correct
byte alignment of the UTF-16 string.
%TRUE if a string could be read, %FALSE otherwise. The string put into @str must be freed with g_free() when no longer needed.
a #GstByteReader instance
address of a #guint16 pointer varieble in which to store the result
Free-function: g_free
Returns a newly-allocated copy of the current data position if there is
a NUL-terminated UTF-32 string in the data (this could be an empty string
as well), and advances the current position.
No input checking for valid UTF-32 is done. This function is endianness
agnostic - you should not assume the UTF-32 characters are in host
endianness.
This function will fail if no NUL-terminator was found in in the data.
Note: there is no peek or get variant of this function to ensure correct
byte alignment of the UTF-32 string.
%TRUE if a string could be read, %FALSE otherwise. The string put into @str must be freed with g_free() when no longer needed.
a #GstByteReader instance
address of a #guint32 pointer varieble in which to store the result
Free-function: g_free
FIXME:Reads (copies) a NUL-terminated string in the #GstByteReader instance,
advancing the current position to the byte after the string. This will work
for any NUL-terminated string with a character width of 8 bits, so ASCII,
UTF-8, ISO-8859-N etc. No input checking for valid UTF-8 is done.
This function will fail if no NUL-terminator was found in in the data.
%TRUE if a string could be read into @str, %FALSE otherwise. The string put into @str must be freed with g_free() when no longer needed.
a #GstByteReader instance
address of a #gchar pointer varieble in which to store the result
Frees a #GstByteReader instance, which was previously allocated by
gst_byte_reader_new().
a #GstByteReader instance
Returns a constant pointer to the current data
position if at least @size bytes are left and
updates the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Size in bytes
address of a #guint8 pointer variable in which to store the result
Read a 32 bit big endian floating point value into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gfloat to store the result
Read a 32 bit little endian floating point value into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gfloat to store the result
Read a 64 bit big endian floating point value into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gdouble to store the result
Read a 64 bit little endian floating point value into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gdouble to store the result
Read a signed 16 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint16 to store the result
Read a signed 16 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint16 to store the result
Read a signed 24 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 24 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 32 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 32 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 64 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint64 to store the result
Read a signed 64 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint64 to store the result
Read a signed 8 bit integer into @val and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint8 to store the result
Returns the current position of a #GstByteReader instance in bytes.
The current position of @reader in bytes.
a #GstByteReader instance
Returns the remaining number of bytes of a #GstByteReader instance.
The remaining number of bytes of @reader instance.
a #GstByteReader instance
Returns the total number of bytes of a #GstByteReader instance.
The total number of bytes of @reader instance.
a #GstByteReader instance
Returns a constant pointer to the current data position if there is
a NUL-terminated string in the data (this could be just a NUL terminator),
advancing the current position to the byte after the string. This will work
for any NUL-terminated string with a character width of 8 bits, so ASCII,
UTF-8, ISO-8859-N etc.
No input checking for valid UTF-8 is done.
This function will fail if no NUL-terminator was found in in the data.
%TRUE if a string could be found, %FALSE otherwise.
a #GstByteReader instance
address of a #gchar pointer varieble in which to store the result
Read an unsigned 16 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint16 to store the result
Read an unsigned 16 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint16 to store the result
Read an unsigned 24 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 24 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 32 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 32 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 64 bit big endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint64 to store the result
Read an unsigned 64 bit little endian integer into @val
and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint64 to store the result
Read an unsigned 8 bit integer into @val and update the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint8 to store the result
Initializes a #GstByteReader instance to read from @data. This function
can be called on already initialized instances.
a #GstByteReader instance
data from which the #GstByteReader should read
Size of @data in bytes
Scan for pattern @pattern with applied mask @mask in the byte reader data,
starting from offset @offset relative to the current position.
The bytes in @pattern and @mask are interpreted left-to-right, regardless
of endianness. All four bytes of the pattern must be present in the
byte reader data for it to match, even if the first or last bytes are masked
out.
It is an error to call this function without making sure that there is
enough data (offset+size bytes) in the byte reader.
offset of the first match, or -1 if no match was found. Example: <programlisting> // Assume the reader contains 0x00 0x01 0x02 ... 0xfe 0xff gst_byte_reader_masked_scan_uint32 (reader, 0xffffffff, 0x00010203, 0, 256); // -> returns 0 gst_byte_reader_masked_scan_uint32 (reader, 0xffffffff, 0x00010203, 1, 255); // -> returns -1 gst_byte_reader_masked_scan_uint32 (reader, 0xffffffff, 0x01020304, 1, 255); // -> returns 1 gst_byte_reader_masked_scan_uint32 (reader, 0xffff, 0x0001, 0, 256); // -> returns -1 gst_byte_reader_masked_scan_uint32 (reader, 0xffff, 0x0203, 0, 256); // -> returns 0 gst_byte_reader_masked_scan_uint32 (reader, 0xffff0000, 0x02030000, 0, 256); // -> returns 2 gst_byte_reader_masked_scan_uint32 (reader, 0xffff0000, 0x02030000, 0, 4); // -> returns -1 </programlisting>
a #GstByteReader
mask to apply to data before matching against @pattern
pattern to match (after mask is applied)
offset from which to start scanning, relative to the current position
number of bytes to scan from offset
Returns a constant pointer to the current data
position if at least @size bytes are left and
keeps the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Size in bytes
address of a #guint8 pointer variable in which to store the result
Read a 32 bit big endian floating point value into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gfloat to store the result
Read a 32 bit little endian floating point value into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gfloat to store the result
Read a 64 bit big endian floating point value into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gdouble to store the result
Read a 64 bit little endian floating point value into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gdouble to store the result
Read a signed 16 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint16 to store the result
Read a signed 16 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint16 to store the result
Read a signed 24 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 24 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 32 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 32 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint32 to store the result
Read a signed 64 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint64 to store the result
Read a signed 64 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint64 to store the result
Read a signed 8 bit integer into @val but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #gint8 to store the result
Returns a constant pointer to the current data position if there is
a NUL-terminated string in the data (this could be just a NUL terminator).
The current position will be maintained. This will work for any
NUL-terminated string with a character width of 8 bits, so ASCII,
UTF-8, ISO-8859-N etc.
No input checking for valid UTF-8 is done.
This function will fail if no NUL-terminator was found in in the data.
%TRUE if a string could be skipped, %FALSE otherwise.
a #GstByteReader instance
address of a #gchar pointer varieble in which to store the result
Read an unsigned 16 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint16 to store the result
Read an unsigned 16 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint16 to store the result
Read an unsigned 24 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 24 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 32 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 32 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint32 to store the result
Read an unsigned 64 bit big endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint64 to store the result
Read an unsigned 64 bit little endian integer into @val
but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint64 to store the result
Read an unsigned 8 bit integer into @val but keep the current position.
%TRUE if successful, %FALSE otherwise.
a #GstByteReader instance
Pointer to a #guint8 to store the result
Sets the new position of a #GstByteReader instance to @pos in bytes.
%TRUE if the position could be set successfully, %FALSE otherwise.
a #GstByteReader instance
The new position in bytes
Skips @nbytes bytes of the #GstByteReader instance.
%TRUE if @nbytes bytes could be skipped, %FALSE otherwise.
a #GstByteReader instance
the number of bytes to skip
Skips a NUL-terminated UTF-16 string in the #GstByteReader instance,
advancing the current position to the byte after the string.
No input checking for valid UTF-16 is done.
This function will fail if no NUL-terminator was found in in the data.
%TRUE if a string could be skipped, %FALSE otherwise.
a #GstByteReader instance
Skips a NUL-terminated UTF-32 string in the #GstByteReader instance,
advancing the current position to the byte after the string.
No input checking for valid UTF-32 is done.
This function will fail if no NUL-terminator was found in in the data.
%TRUE if a string could be skipped, %FALSE otherwise.
a #GstByteReader instance
Skips a NUL-terminated string in the #GstByteReader instance, advancing
the current position to the byte after the string. This will work for
any NUL-terminated string with a character width of 8 bits, so ASCII,
UTF-8, ISO-8859-N etc. No input checking for valid UTF-8 is done.
This function will fail if no NUL-terminator was found in in the data.
%TRUE if a string could be skipped, %FALSE otherwise.
a #GstByteReader instance
Create a new #GstByteReader instance, which will read from @data.
Free-function: gst_byte_reader_free
a new #GstByteReader instance
data from which the #GstByteReader should read
Size of @data in bytes
#GstByteWriter provides a byte writer and reader that can write/read different
integer and floating point types to/from a memory buffer. It provides functions
for writing/reading signed/unsigned, little/big endian integers of 8, 16, 24,
32 and 64 bits and functions for reading little/big endian floating points numbers of
32 and 64 bits. It also provides functions to write/read NUL-terminated strings
in various character encodings.
Checks if enough free space from the current write cursor is
available and reallocates if necessary.
%TRUE if at least @size bytes are still available
#GstByteWriter instance
Number of bytes that should be available
Writes @size bytes containing @value to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to be writen
Number of bytes to be writen
Frees @writer and all memory allocated by it.
#GstByteWriter instance
Frees @writer and all memory allocated by it except
the current data, which is returned as #GstBuffer.
Free-function: gst_buffer_unref
the current data as buffer. gst_buffer_unref() after usage.
#GstByteWriter instance
Frees @writer and all memory allocated by it except
the current data, which is returned.
Free-function: g_free
the current data. g_free() after usage.
#GstByteWriter instance
Returns the remaining size of data that can still be written. If
-1 is returned the remaining size is only limited by system resources.
the remaining size of data that can still be written
#GstByteWriter instance
Initializes @writer to an empty instance
#GstByteWriter instance
Initializes @writer with the given
memory area. If @initialized is %TRUE it is possible to
read @size bytes from the #GstByteWriter from the beginning.
#GstByteWriter instance
Memory area for writing
Size of @data in bytes
If %TRUE the complete data can be read from the beginning
Initializes @writer with the given initial data size.
#GstByteWriter instance
Initial size of data
If %TRUE the data can't be reallocated
Writes @size bytes of @data to @writer.
%TRUE if the data could be written
#GstByteWriter instance
source #GstBuffer
offset to copy from
total size to copy. If -1, all data is copied
Writes @size bytes of @data to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Data to write
Size of @data in bytes
Writes a big endian 32 bit float to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a little endian 32 bit float to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a big endian 64 bit float to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a little endian 64 bit float to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed big endian 16 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed little endian 16 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed big endian 24 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed little endian 24 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed big endian 32 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed little endian 32 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed big endian 64 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed little endian 64 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a signed 8 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a NUL-terminated UTF16 string to @writer (including the terminator).
%TRUE if the value could be written
#GstByteWriter instance
UTF16 string to write
Writes a NUL-terminated UTF32 string to @writer (including the terminator).
%TRUE if the value could be written
#GstByteWriter instance
UTF32 string to write
Writes a NUL-terminated UTF8 string to @writer (including the terminator).
%TRUE if the value could be written
#GstByteWriter instance
UTF8 string to write
Writes a unsigned big endian 16 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned little endian 16 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned big endian 24 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned little endian 24 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned big endian 32 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned little endian 32 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned big endian 64 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned little endian 64 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Writes a unsigned 8 bit integer to @writer.
%TRUE if the value could be written
#GstByteWriter instance
Value to write
Resets @writer and frees the data if it's
owned by @writer.
#GstByteWriter instance
Resets @writer and returns the current data as buffer.
Free-function: gst_buffer_unref
the current data as buffer. gst_buffer_unref() after usage.
#GstByteWriter instance
Resets @writer and returns the current data.
Free-function: g_free
the current data. g_free() after usage.
#GstByteWriter instance
Creates a new, empty #GstByteWriter instance
Free-function: gst_byte_writer_free
a new, empty #GstByteWriter instance
Creates a new #GstByteWriter instance with the given
memory area. If @initialized is %TRUE it is possible to
read @size bytes from the #GstByteWriter from the beginning.
Free-function: gst_byte_writer_free
a new #GstByteWriter instance
Memory area for writing
Size of @data in bytes
If %TRUE the complete data can be read from the beginning
Creates a new #GstByteWriter instance with the given
initial data size.
Free-function: gst_byte_writer_free
a new #GstByteWriter instance
Initial size of data
If %TRUE the data can't be reallocated
Structure used by the collect_pads.
A function that will be called when the #GstCollectData will be freed.
It is passed the pointer to the structure and should free any custom
memory and resources allocated for it.
the #GstCollectData that will be freed
Manages a set of pads that operate in collect mode. This means that control
is given to the manager of this object when all pads have data.
<itemizedlist>
<listitem><para>
Collectpads are created with gst_collect_pads_new(). A callback should then
be installed with gst_collect_pads_set_function ().
</para></listitem>
<listitem><para>
Pads are added to the collection with gst_collect_pads_add_pad()/
gst_collect_pads_remove_pad(). The pad
has to be a sinkpad. The chain and event functions of the pad are
overridden. The element_private of the pad is used to store
private information for the collectpads.
</para></listitem>
<listitem><para>
For each pad, data is queued in the _chain function or by
performing a pull_range.
</para></listitem>
<listitem><para>
When data is queued on all pads in waiting mode, the callback function is called.
</para></listitem>
<listitem><para>
Data can be dequeued from the pad with the gst_collect_pads_pop() method.
One can peek at the data with the gst_collect_pads_peek() function.
These functions will return NULL if the pad received an EOS event. When all
pads return NULL from a gst_collect_pads_peek(), the element can emit an EOS
event itself.
</para></listitem>
<listitem><para>
Data can also be dequeued in byte units using the gst_collect_pads_available(),
gst_collect_pads_read() and gst_collect_pads_flush() calls.
</para></listitem>
<listitem><para>
Elements should call gst_collect_pads_start() and gst_collect_pads_stop() in
their state change functions to start and stop the processing of the collectpads.
The gst_collect_pads_stop() call should be called before calling the parent
element state change function in the PAUSED_TO_READY state change to ensure
no pad is blocked and the element can finish streaming.
</para></listitem>
<listitem><para>
gst_collect_pads_collect() and gst_collect_pads_collect_range() can be used by
elements that start a #GstTask to drive the collect_pads. This feature is however
not yet implemented.
</para></listitem>
<listitem><para>
gst_collect_pads_set_waiting() sets a pad to waiting or non-waiting mode.
CollectPads element is not waiting for data to be collected on non-waiting pads.
Thus these pads may but need not have data when the callback is called.
All pads are in waiting mode by default.
</para></listitem>
</itemizedlist>
Last reviewed on 2011-10-28 (0.10.36)
Create a new instance of #GstCollectPads.
MT safe.
a new #GstCollectPads, or NULL in case of an error.
Add a pad to the collection of collect pads. The pad has to be
a sinkpad. The refcount of the pad is incremented. Use
gst_collect_pads_remove_pad() to remove the pad from the collection
again.
You specify a size for the returned #GstCollectData structure
so that you can use it to store additional information.
You can also specify a #GstCollectDataDestroyNotify that will be called
just before the #GstCollectData structure is freed. It is passed the
pointer to the structure and should free any custom memory and resources
allocated for it.
Keeping a pad locked in waiting state is only relevant when using
the default collection algorithm (providing the oldest buffer).
It ensures a buffer must be available on this pad for a collection
to take place. This is of typical use to a muxer element where
non-subtitle streams should always be in waiting state,
e.g. to assure that caps information is available on all these streams
when initial headers have to be written.
The pad will be automatically activated in push mode when @pads is
started.
MT safe.
a new #GstCollectData to identify the new pad. Or NULL if wrong parameters are supplied.
the collectpads to use
the pad to add
the size of the returned #GstCollectData structure
function to be called before the returned #GstCollectData structure is freed
whether to lock this pad in usual waiting state
Query how much bytes can be read from each queued buffer. This means
that the result of this call is the maximum number of bytes that can
be read from each of the pads.
This function should be called with @pads STREAM_LOCK held, such as
in the callback.
MT safe.
The maximum number of bytes queued on all pads. This function returns 0 if a pad has no queued buffer.
the collectpads to query
Convenience clipping function that converts incoming buffer's timestamp
to running time, or clips the buffer if outside configured segment.
the collectpads to use
collect data of corresponding pad
buffer being clipped
output buffer with running time, or NULL if clipped
user data (unused)
Default GstCollectPads event handling that elements should always
chain up to to ensure proper operation. Element might however indicate
event should not be forwarded downstream.
the collectpads to use
collect data of corresponding pad
event being processed
process but do not send event downstream
Flush @size bytes from the pad @data.
This function should be called with @pads STREAM_LOCK held, such as
in the callback.
MT safe.
The number of bytes flushed This can be less than @size and is 0 if the pad was end-of-stream.
the collectpads to query
the data to use
the number of bytes to flush
Peek at the buffer currently queued in @data. This function
should be called with the @pads STREAM_LOCK held, such as in the callback
handler.
MT safe.
The buffer in @data or NULL if no buffer is queued. should unref the buffer after usage.
the collectpads to peek
the data to use
Pop the buffer currently queued in @data. This function
should be called with the @pads STREAM_LOCK held, such as in the callback
handler.
MT safe.
The buffer in @data or NULL if no buffer was queued. You should unref the buffer after usage.
the collectpads to pop
the data to use
Default GstCollectPads query handling that elements should always
chain up to to ensure proper operation. Element might however indicate
query should not be forwarded downstream.
the collectpads to use
collect data of corresponding pad
query being processed
process but do not send event downstream
Get a subbuffer of @size bytes from the given pad @data.
This function should be called with @pads STREAM_LOCK held, such as in the
callback.
MT safe.
A sub buffer. The size of the buffer can be less that requested. A return of NULL signals that the pad is end-of-stream. Unref the buffer after use.
the collectpads to query
the data to use
the number of bytes to read
Remove a pad from the collection of collect pads. This function will also
free the #GstCollectData and all the resources that were allocated with
gst_collect_pads_add_pad().
The pad will be deactivated automatically when @pads is stopped.
MT safe.
%TRUE if the pad could be removed.
the collectpads to use
the pad to remove
Set the callback function and user data that will be called with
the oldest buffer when all pads have been collected, or NULL on EOS.
If a buffer is passed, the callback owns a reference and must unref
it.
MT safe.
the collectpads to use
the function to set
user data passed to the function
Install a clipping function that is called right after a buffer is received
on a pad managed by @pads. See #GstCollectPadsClipFunction for more info.
the collectpads to use
clip function to install
user data to pass to @clip_func
Set the timestamp comparison function.
MT safe.
the pads to use
the function to set
user data passed to the function
Set the event callback function and user data that will be called when
collectpads has received an event originating from one of the collected
pads. If the event being processed is a serialized one, this callback is
called with @pads STREAM_LOCK held, otherwise not. As this lock should be
held when calling a number of CollectPads functions, it should be acquired
if so (unusually) needed.
MT safe.
the collectpads to use
the function to set
user data passed to the function
Change the flushing state of all the pads in the collection. No pad
is able to accept anymore data when @flushing is %TRUE. Calling this
function with @flushing %FALSE makes @pads accept data again.
Caller must ensure that downstream streaming (thread) is not blocked,
e.g. by sending a FLUSH_START downstream.
MT safe.
the collectpads to use
desired state of the pads
CollectPads provides a default collection algorithm that will determine
the oldest buffer available on all of its pads, and then delegate
to a configured callback.
However, if circumstances are more complicated and/or more control
is desired, this sets a callback that will be invoked instead when
all the pads added to the collection have buffers queued.
Evidently, this callback is not compatible with
gst_collect_pads_set_buffer_function() callback.
If this callback is set, the former will be unset.
MT safe.
the collectpads to use
the function to set
user data passed to the function
Set the query callback function and user data that will be called after
collectpads has received a query originating from one of the collected
pads. If the query being processed is a serialized one, this callback is
called with @pads STREAM_LOCK held, otherwise not. As this lock should be
held when calling a number of CollectPads functions, it should be acquired
if so (unusually) needed.
MT safe.
the collectpads to use
the function to set
user data passed to the function
Sets a pad to waiting or non-waiting mode, if at least this pad
has not been created with locked waiting state,
in which case nothing happens.
This function should be called with @pads STREAM_LOCK held, such as
in the callback.
MT safe.
the collectpads
the data to use
boolean indicating whether this pad should operate in waiting or non-waiting mode
Starts the processing of data in the collect_pads.
MT safe.
the collectpads to use
Stops the processing of data in the collect_pads. this function
will also unblock any blocking operations.
MT safe.
the collectpads to use
Get a subbuffer of @size bytes from the given pad @data. Flushes the amount
of read bytes.
This function should be called with @pads STREAM_LOCK held, such as in the
callback.
MT safe.
A sub buffer. The size of the buffer can be less that requested. A return of NULL signals that the pad is end-of-stream. Unref the buffer after use.
the collectpads to query
the data to use
the number of bytes to read
A function that will be called when a (considered oldest) buffer can be muxed.
If all pads have reached EOS, this function is called with NULL @buffer
and NULL @data.
#GST_FLOW_OK for success
the #GstCollectPads that trigered the callback
the #GstCollectData of pad that has received the buffer
the #GstBuffer
user data passed to gst_collect_pads_set_buffer_function()
A function that will be called when @inbuffer is received on the pad managed
by @data in the collecpad object @pads.
The function should use the segment of @data and the negotiated media type on
the pad to perform clipping of @inbuffer.
This function takes ownership of @inbuffer and should output a buffer in
@outbuffer or return %NULL in @outbuffer if the buffer should be dropped.
a #GstFlowReturn that corresponds to the result of clipping.
a #GstCollectPads
a #GstCollectData
the input #GstBuffer
the output #GstBuffer
user data
A function for comparing two timestamps of buffers or newsegments collected on one pad.
Integer less than zero when first timestamp is deemed older than the second one. Zero if the timestamps are deemed equally old. Integer greate than zero when second timestamp is deemed older than the first one.
the #GstCollectPads that is comparing the timestamps
the first #GstCollectData
the first timestamp
the second #GstCollectData
the second timestamp
user data passed to gst_collect_pads_set_compare_function()
A function that will be called while processing an event. It takes
ownership of the event and is responsible for chaining up (to
gst_collect_pads_event_default()) or dropping events (such typical cases
being handled by the default handler).
%TRUE if the pad could handle the event
the #GstCollectPads that trigered the callback
the #GstPad that received an event
the #GstEvent received
user data passed to gst_collect_pads_set_event_function()
A function that will be called when all pads have received data.
#GST_FLOW_OK for success
the #GstCollectPads that trigered the callback
user data passed to gst_collect_pads_set_function()
A function that will be called while processing a query. It takes
ownership of the query and is responsible for chaining up (to
events downstream (with gst_pad_event_default()).
%TRUE if the pad could handle the event
the #GstCollectPads that trigered the callback
the #GstPad that received an event
the #GstEvent received
user data passed to gst_collect_pads_set_query_function()
Set if collectdata's pad is EOS.
Set if collectdata's pad is flushing.
Set if collectdata's pad received a new_segment event.
Set if collectdata's pad must be waited for when collecting.
Set collectdata's pad WAITING state must not be changed. #GstCollectPadsStateFlags indicate private state of a collectdata('s pad).
This class is mostly useful for elements that cannot do
random access, or at least very slowly. The source usually
prefers to push out a fixed size buffer.
Subclasses usually operate in a format that is different from the
default GST_FORMAT_BYTES format of #GstBaseSrc.
Classes extending this base class will usually be scheduled
in a push based mode. If the peer accepts to operate without
offsets and within the limits of the allowed block size, this
class can operate in getrange based mode automatically. To make
this possible, the subclass should implement and override the
SCHEDULING query.
The subclass should extend the methods from the baseclass in
addition to the ::create method.
Seeking, flushing, scheduling and sync is all handled by this
base class.
Last reviewed on 2006-07-04 (0.10.9)
This function will be called by gst_type_find_helper_get_range() when
typefinding functions request to peek at the data of a stream at certain
offsets. If this function returns GST_FLOW_OK, the result buffer will be
stored in @buffer. The contents of @buffer is invalid for any other
return value.
This function is supposed to behave exactly like a #GstPadGetRangeFunction.
GST_FLOW_OK for success
a #GstObject that will handle the getrange request
the parent of @obj or NULL
the offset of the range
the length of the range
a memory location to hold the result buffer
Tries to find what type of data is flowing from the given source #GstPad.
Free-function: gst_caps_unref
the #GstCaps corresponding to the data stream. Returns #NULL if no #GstCaps matches the data stream.
A source #GstPad
The length in bytes
Tries to find what type of data is contained in the given #GstBuffer, the
assumption being that the buffer represents the beginning of the stream or
file.
All available typefinders will be called on the data in order of rank. If
a typefinding function returns a probability of #GST_TYPE_FIND_MAXIMUM,
typefinding is stopped immediately and the found caps will be returned
right away. Otherwise, all available typefind functions will the tried,
and the caps with the highest probability will be returned, or #NULL if
the content of the buffer could not be identified.
Free-function: gst_caps_unref
the #GstCaps corresponding to the data, or #NULL if no type could be found. The caller should free the caps returned with gst_caps_unref().
object doing the typefinding, or NULL (used for logging)
a #GstBuffer with data to typefind
location to store the probability of the found caps, or #NULL
Tries to find what type of data is contained in the given @data, the
assumption being that the data represents the beginning of the stream or
file.
All available typefinders will be called on the data in order of rank. If
a typefinding function returns a probability of #GST_TYPE_FIND_MAXIMUM,
typefinding is stopped immediately and the found caps will be returned
right away. Otherwise, all available typefind functions will the tried,
and the caps with the highest probability will be returned, or #NULL if
the content of @data could not be identified.
Free-function: gst_caps_unref
the #GstCaps corresponding to the data, or #NULL if no type could be found. The caller should free the caps returned with gst_caps_unref().
object doing the typefinding, or NULL (used for logging)
a pointer with data to typefind
the size of @data
location to store the probability of the found caps, or #NULL
Tries to find the best #GstCaps associated with @extension.
All available typefinders will be checked against the extension in order
of rank. The caps of the first typefinder that can handle @extension will be
returned.
Free-function: gst_caps_unref
the #GstCaps corresponding to @extension, or #NULL if no type could be found. The caller should free the caps returned with gst_caps_unref().
object doing the typefinding, or NULL (used for logging)
an extension
Utility function to do pull-based typefinding. Unlike gst_type_find_helper()
however, this function will use the specified function @func to obtain the
data needed by the typefind functions, rather than operating on a given
source pad. This is useful mostly for elements like tag demuxers which
strip off data at the beginning and/or end of a file and want to typefind
the stripped data stream before adding their own source pad (the specified
callback can then call the upstream peer pad with offsets adjusted for the
tag size, for example).
When @extension is not NULL, this function will first try the typefind
functions for the given extension, which might speed up the typefinding
in many cases.
Free-function: gst_caps_unref
the #GstCaps corresponding to the data stream. Returns #NULL if no #GstCaps matches the data stream.
A #GstObject that will be passed as first argument to @func
the parent of @obj or NULL
A generic #GstTypeFindHelperGetRangeFunction that will be used to access data at random offsets when doing the typefinding
The length in bytes
extension of the media
location to store the probability of the found caps, or #NULL