[FFmpeg-trac] #6983(avcodec:new): AAC encoder breaking 5.1 channels

FFmpeg trac at avcodec.org
Thu Jan 25 17:53:55 EET 2018


#6983: AAC encoder breaking 5.1 channels
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             Reporter:  elsiko   |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  avcodec  |                  Version:  git-master
             Keywords:           |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
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 Summary of the bug:
 For a long time now, I've been doing some encodings into x265/aac using
 ffmpeg.
 Recently I started noticing a problem with the audio channels that get - I
 think - mixed up.

 The original file media info would show:
 `Front: L C R, Side: L R, LFE`

 But the encoded file will show:
 `Front: L C R, Side: C, Back: L R`

 I'm no expert, but I think the LFE channel is either dropped or converted.
 I think this behaviour started around December 2017.

 To be certain that something indeed changed, I encoded a file twice, used
 two static builds (from here: https://johnvansickle.com/ffmpeg/), once
 using a build from 2017-09-02, and one from 2018-01-24.

 I attached to the tickets the logs of both encodings, the media info (+
 the original).
 You can download the original mkv file, as well as encoded files from
 there: http://176.9.126.245/encoding-results/

 You can clearly see in the mediainfo of 2017 that the channels were
 correct (with LFE), but that's not the case in the 2018 encoding.

 One last thing, I think this problem might be related to this ticket:
 https://trac.ffmpeg.org/ticket/6965

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Ticket URL: <https://trac.ffmpeg.org/ticket/6983>
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