[FFmpeg-trac] #9057(undetermined:new): AAC 7.1 channels mixed up in decoding

FFmpeg trac at avcodec.org
Wed Jan 6 17:20:00 EET 2021


#9057: AAC 7.1 channels mixed up in decoding
-------------------------------------+-------------------------------------
             Reporter:  kmamal       |                     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:

 I have an 8 channel audio file that I'm encoding as AAC. When inspecting
 the channels of the created aac file using ffmpeg, they appear to be in
 the wrong order or even added together.

 This appears to be a problem in decoding, as inspecting the aac file with
 other software (I used Audacity) shows the channels in the correct order.

 This problem appeared in ffmpeg 4.3. In ffmpeg 4.2.4 the channels are ok.

 How to reproduce:

 I'm using the 8_Channel_ID.wav file attached to this ticket.
 I'm encoding to AAC using:

 {{{ffmpeg -i 8_Channel_ID.wav out.aac}}}

 First I inspect the channels using:

 {{{ffmpeg -i out.aac -filter_complex
 "showwavespic=s=1280x480:split_channels=1" -frames:v 1 -f image2 - |
 display}}}

 The result looks like the first two channels have been swapped with the
 last two.

 Then I inspect the channels using:

 {{{ffmpeg -i out.aac -filter_complex
 "channelsplit=channel_layout=7.1,join=inputs=8:channel_layout=7.1,showwavespic=s=1280x480:split_channels=1"
 -frames:v 1 -f image2 - | display}}}

 The result looks like the last two channels have been added to the first
 two.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/9057>
FFmpeg <https://ffmpeg.org>
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