mp3_file.rb in mp3file-1.2.0

- old
+ new

@@ -123,12 +123,29 @@
       # Some files have more than one ID3v2 tag. If we can't find an
       # MP3 header in the next 4k, try reading another ID3v2 tag and
       # repeat.
       @extra_id3v2_tags = []
       begin
-        # Try to find the first MP3 header.
-        @first_header_offset, @first_header = get_next_header(@file)
+        # Try to find the first two MP3 headers.
+        loop do
+          @first_header_offset, @first_header = get_next_header(@file)
+          @file.seek(@first_header_offset + @first_header.frame_size, IO::SEEK_SET)
+          second_header_offset = @file.tell - 4
+          second_header =
+            begin
+              MP3Header.new(@file)
+            rescue InvalidMP3HeaderError
+              nil
+            end
+
+          # Pretend we didn't read the second header.
+          @file.seek(@first_header_offset + 4)
+
+          if second_header && @first_header.same_header?(second_header)
+            break
+          end
+        end
       rescue InvalidMP3FileError
         if @id3v2_tag
           end_of_tags = @id3v2_tag.size + @extra_id3v2_tags.map(&:last).map(&:size).reduce(:+).to_i
           @file.seek(end_of_tags, IO::SEEK_SET)
 
@@ -204,35 +221,45 @@
         # / CBR call. Assume that Xing headers, when present in a CBR
         # file, are called "Info".
         @vbr = !@xing_header.nil? && @xing_header.name == "Xing"
       end
 
-      # puts "@num_frames = #{@num_frames.inspect}"
-      # puts "@xing_header = #{@xing_header.inspect}"
+      # puts "@num_frames (1) = #{@num_frames.inspect}"
+      # puts "@bitrate (1) = #{@bitrate.inspect}"
+      # puts "@vbr = #{@vbr.inspect}"
+      # puts "@xing_header.frames = #{@xing_header && @xing_header.frames.inspect}"
+      # puts "@xing_header.bytes = #{@xing_header && @xing_header.bytes.inspect}"
       # puts "@audio_size = #{@audio_size.inspect}"
       # puts "@first_header size = #{@first_header.frame_size.inspect}"
 
-      # Find the number of frames. Prefer the actual frame count we
-      # did (if we scanned all the frames) over the Xing
-      # header. Prefer the Xing header over file size math.
-      @num_frames = @num_frames ||
-        (@xing_header && (@xing_header.frames + 1)) ||
+      # Find the number of frames, in this order:
+      # 1. The frame count from the Xing (or Info) header.
+      # 2. The number of frames we actually counted by scanning the
+      #    whole file, which we might not have done.
+      # 3. Assume it's CBR and divide the file size by the frame size.
+      @num_frames = 
+        (@xing_header && @xing_header.frames) ||
+        @num_frames ||
         (@audio_size / @first_header.frame_size)
 
+      # puts "@num_frames (2) = #{@num_frames.inspect}"
+
       # Figure out the total samples and the time duration.
       @total_samples = @num_frames * @first_header.samples
       @length = @total_samples.to_f / @samplerate.to_f
 
+      # puts "@total_samples = #{@total_samples.inspect}"
+      # puts "@length = #{@length.inspect}"
+
       # If the file looks like it's a VBR file, do an averate bitrate
       # calculation, either using the Xing header's idea of the file
       # size or the one we found.
       if @vbr
         @bitrate = ((@xing_header && @xing_header.bytes) || @audio_size) / @length.to_f * 8 / 1000
       end
 
-      # puts "@vbr = #{@vbr.inspect}"
-      # puts "@bitrate = #{@bitrate.inspect}"
+      # puts "@bitrate (2) = #{@bitrate.inspect}"
 
       @file.close
     end
 
     def get_next_header(file, offset = nil)
@@ -245,10 +272,10 @@
       header_offset = file.tell
 
       while header.nil?
         begin
           header = MP3Header.new(file)
-          header_offset = file.tell - 4
+          header_offset = file.tell - 4          
         rescue InvalidMP3HeaderError
           header_offset += 1
           if header_offset - initial_header_offset > 4096
             raise InvalidMP3FileError, "Could not find a valid MP3 header in the first 4096 bytes."
           else