[FFmpeg-trac] #7447(undetermined:new): Decoding ogg (vorbis) appends extra samples to output

FFmpeg trac at avcodec.org
Wed Sep 19 21:32:17 EEST 2018

#7447: Decoding ogg (vorbis) appends extra samples to output
             Reporter:  evesira      |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Summary of the bug:

 ffmpeg incorrectly decodes ogg (vorbis) files, appending extra samples at
 the end of the audio output. The amount of samples added doesn't seem to
 be correlated to file size or anything else. The added samples seem to
 always be digital silence.

 This ticket stemmed from this issue reported in the Chrome browser:

 This issue causes the inability to seamlessly and correctly loop layered
 and synced ogg tracks of the same exact length after they have been
 decoded by ffmpeg.

 Vorbis was designed to be capable of sample-perfect looping, so being able
 to reconstruct the file exactly is possible and necessary.

 How to reproduce:

 % ffmpeg -i test.ogg test.wav
 ffmpeg version: ffmpeg-20180919-e33b28c-win64-static (Zeranoe)

 Test ogg file:
 input file is exactly 6.00 seconds long, or 264,600 samples at 44.1 kHz
 output file is 265,536 samples long, 936 samples added

 Other softwares that support loading of oggs, such as Audacity, Wavosaur,
 Ocen, etc (which presumably use libvorbis and not ffmpeg), correctly
 decode the test file as 264,600 samples long.

Ticket URL: <https://trac.ffmpeg.org/ticket/7447>
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