Answers.Body: <p>AC3 doesn't support 7.1.  Only took like 25 hours of messing with the filter chain to figure it out.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-06-27T23:18:40.103Z
Answers.LastActivityDate: 2023-06-27T23:18:40.103Z
Answers.UserDisplayName: Bryan Austin
Body: <p>I am trying to reconstruct a 7.1 channel output after processing, and ffmpeg keeps outputting a <code>5.0(side)</code>. (trimmed for readability)</p>
  <pre><code>ffmpeg -i &quot;intermediate/refined.mka&quot; -i &quot;intermediate/extracted.data&quot; -filter_complex &quot;\
  ...
  [ml9][mr9][mc2][ms1][mm2][mt2][mw2][me2]amerge=inputs=8,aformat=channel_layouts=7.1[out]&quot; -map &quot;[out]&quot; &quot;intermediate/mixed.mka&quot;
  </code></pre>
  <p>Output:</p>
  <pre><code>...
  Input #0, matroska,webm, from 'intermediate/refined.mka':
      Stream #0:0: Audio: wavpack, 44100 Hz, stereo, fltp
  ...
  Input #1, dts, from 'intermediate/extracted.data':
      Stream #1:0: Audio: dts (DTS-HD MA), 48000 Hz, 7.1, s32p (24 bit)
  ...
  Output #0, matroska, to 'intermediate/mixed.mka':
      Stream #0:0: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.0(side), fltp, 448 kb/s
  </code></pre>
  <p>I am feeding 8 mono channels into <code>amerge</code> and adding the 7.1 <code>aformat</code> constraint, and it gives me a 5.0 without warning or error. By everything I've read in the docs <code>amerge</code> should only add channels, never discarding them. Any idea what's going on here?</p>
  
Tags: <ffmpeg>
Title: ffmpeg amerge ignoring channel layout
UserDisplayName: Bryan Austin
ThreadText: # ffmpeg amerge ignoring channel layout
  
  (Asked by: username_0 on 2023-06-18)
  
  I am trying to reconstruct a 7.1 channel output after processing, and ffmpeg keeps outputting a `5.0(side)`. (trimmed for readability)
  
  ```
  ffmpeg -i "intermediate/refined.mka" -i "intermediate/extracted.data" -filter_complex "\
  ...
  [ml9][mr9][mc2][ms1][mm2][mt2][mw2][me2]amerge=inputs=8,aformat=channel_layouts=7.1[out]" -map "[out]" "intermediate/mixed.mka"
  
  ```
  
  Output:
  
  ```
  ...
  Input #0, matroska,webm, from 'intermediate/refined.mka':
      Stream #0:0: Audio: wavpack, 44100 Hz, stereo, fltp
  ...
  Input #1, dts, from 'intermediate/extracted.data':
      Stream #1:0: Audio: dts (DTS-HD MA), 48000 Hz, 7.1, s32p (24 bit)
  ...
  Output #0, matroska, to 'intermediate/mixed.mka':
      Stream #0:0: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.0(side), fltp, 448 kb/s
  
  ```
  
  I am feeding 8 mono channels into `amerge` and adding the 7.1 `aformat` constraint, and it gives me a 5.0 without warning or error. By everything I've read in the docs `amerge` should only add channels, never discarding them. Any idea what's going on here?
  
  **Tags:** ffmpeg
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_0 on 2023-06-27. Score: 0 | Accepted answer
  
  AC3 doesn't support 7.1. Only took like 25 hours of messing with the filter chain to figure it out.
  
  
  ---
  
  