module AviGlitch
# Base is the object that provides interfaces mainly used.
# To glitch, and save file. The instance is returned through AviGlitch#open.
#
class Base
# AviGlitch::Frames object generated from the +file+.
attr_reader :frames
# The input file (copied tempfile).
attr_reader :file
##
# Creates a new instance of AviGlitch::Base, open the file and
# make it ready to manipulate.
# It requires +path+ as Pathname.
def initialize path
File.open(path, 'rb') do |f|
# copy as tempfile
@file = Tempfile.open 'aviglitch'
f.rewind
while d = f.read(1024) do
@file.print d
end
end
unless AviGlitch::Base.surely_formatted? @file
raise 'Unsupported file passed.'
end
@frames = Frames.new @file
# I believe Ruby's GC to close and remove the Tempfile..
end
##
# Outputs the glitched file to +path+, and close the file.
def output path, do_file_close = true
FileUtils.cp @file.path, path
close if do_file_close
self
end
##
# An explicit file close.
def close
@file.close!
end
##
# Glitches each frame data.
# It is a convenient method to iterate each frame.
#
# The argument +target+ takes symbols listed below:
# [:keyframe or :iframe] select video key frames (aka I-frame)
# [:deltaframe or :pframe] select video delta frames (difference frames)
# [:videoframe] select both of keyframe and deltaframe
# [:audioframe] select audio frames
# [:all] select all frames
#
# It also requires a block. In the block, you take the frame data
# as a String parameter.
# To modify the data, simply return a modified data.
# It returns +self+
def glitch target = :all, &block # :yield: data
@frames.each do |frame|
if valid_target? target, frame
frame.data = yield frame.data
end
end
self
end
##
# Do glitch with index.
def glitch_with_index target = :all, &block # :yield: data, index
i = 0
@frames.each do |frame|
if valid_target? target, frame
frame.data = yield(frame.data, i)
i += 1
end
end
self
end
##
# Clears all (or in +range+) keyframes to deltaframes.
# It's an alias for Frames#clear_keyframes!
def clear_keyframes! range = nil
self.frames.clear_keyframes! range
self
end
##
# Swaps the frames with other Frames data.
def frames= other
raise TypeError unless other.kind_of?(Frames)
@frames.clear
@frames.concat other
end
alias_method :write, :output
def valid_target? target, frame #:nodoc:
return true if target == :all
begin
frame.send "is_#{target.to_s.sub(/frames$/, 'frame')}?"
rescue
false
end
end
private :valid_target?
class << self
##
# Checks if the +file+ is a correctly formetted AVI file.
# +file+ can be String or Pathname or IO.
def surely_formatted? file, debug = false
answer = true
is_io = file.respond_to?(:seek) # Probably IO.
file = File.open(file, 'rb') unless is_io
begin
file.seek 0, IO::SEEK_END
eof = file.pos
file.rewind
unless file.read(4) == 'RIFF'
answer = false
warn 'RIFF sign is not found' if debug
end
len = file.read(4).unpack('V').first
unless file.read(4) == 'AVI '
answer = false
warn 'AVI sign is not found' if debug
end
while file.read(4) =~ /^(?:LIST|JUNK)$/ do
s = file.read(4).unpack('V').first
file.pos += s
end
file.pos -= 4
# we require idx1
unless file.read(4) == 'idx1'
answer = false
warn 'idx1 is not found' if debug
end
s = file.read(4).unpack('V').first
file.pos += s
rescue => err
warn err.message if debug
answer = false
ensure
file.close unless is_io
end
answer
end
end
end
end