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Old 5th April 2011, 09:58   #1  |  Link
AlanJames1987
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FFMPEG 5.1 Sound Misplaced

When converting video on Linux from an 5.1 source to an AAC 5.1 source my channels get mapped incorrectly. The most noticeable problem is the sound from the center speaker comes out of the front right speaker. I am using the latest Git version on Ubuntu 10.04. Can anyone help me figure out why this is happening?

Here is an example of a video I converted.
http://www.alanjames1987.com/develop...hannelTest.zip
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Last edited by AlanJames1987; 5th April 2011 at 10:09. Reason: Added Example
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Old 5th April 2011, 14:23   #2  |  Link
MickJT
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ffmpeg revision and command line options? Also, ffprobe output of the source material.
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Old 5th April 2011, 14:55   #3  |  Link
poisondeathray
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channel mapping convention is different for AC3 and AAC

see remark 1:
http://avisynth.org/mediawiki/GetChannel
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Old 5th April 2011, 16:26   #4  |  Link
AlanJames1987
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FFMPEG Command
Code:
ffmpeg -i $originalsVideosDir/$1.* \
  -vcodec libx264 -vf 'scale=1920:-1' -b 1920k \
  -acodec aac -strict experimental $outputAudioChannels -ab 192k \
  -vpre $renderSpeed -threads 0 -map_metadata -1 -y $tempDir/$1_hd.mp4
qt-faststart $tempDir/$1_hd.mp4 $finalsVideosDir/$1.mp4
FFPROBE
Code:
FFprobe version git-N-28456-g1c31b26, Copyright (c) 2007-2011 the FFmpeg developers
  built on Mar 17 2011 12:49:56 with gcc 4.4.3
  configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libfaac --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-x11grab
  libavutil    50. 39. 0 / 50. 39. 0
  libavcodec   52.114. 0 / 52.114. 0
  libavformat  52.103. 0 / 52.103. 0
  libavdevice  52.  3. 0 / 52.  3. 0
  libavfilter   1. 76. 0 /  1. 76. 0
  libswscale    0. 12. 0 /  0. 12. 0
  libpostproc  51.  2. 0 / 51.  2. 0
[matroska,webm @ 0x20770d0] Estimating duration from bitrate, this may be inaccurate
Input #0, matroska,webm, from '11.mkv':
  Duration: 00:01:04.39, start: 0.000000, bitrate: 1536 kb/s
    Stream #0.0(eng): Video: h264 (High), yuv420p, 1920x816 [PAR 1:1 DAR 40:17], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc
    Metadata:
      title           : Tron.Legacy.2010.BluRay.1080p.x264.DTS-MySiLU
    Stream #0.1(eng): Audio: dca (DTS), 48000 Hz, 5.1, s16, 1536 kb/s (default)
I am using the aac codec within FFMPEG because it is creating a better sounding file. However, using libfaac produces the same incorrectly mapped channels.

poisondeathray that link seems to be not working right now.
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Last edited by AlanJames1987; 5th April 2011 at 17:56.
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Old 5th April 2011, 16:35   #5  |  Link
poisondeathray
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Quote:
Originally Posted by AlanJames1987 View Post
poisondeathray that link seems to be not working right now.
you can use googlecache to view it
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Old 5th April 2011, 18:02   #6  |  Link
AlanJames1987
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Quote:
you can use googlecache to view it
Thanks. I viewed it that way and understand the different formats now. My next question is, how can I use that knowledge to correct the problem?
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Old 5th April 2011, 18:07   #7  |  Link
poisondeathray
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you can remap the channels

not sure how you would do that in linux

you could remap in avisynth, or use eac3to , wavewizard, or any audio editor on pc
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Old 6th April 2011, 21:47   #8  |  Link
AlanJames1987
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I found a Linux program called SOX that might be able to fix my problem. Has anyone ever used SOX?
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Old 7th April 2011, 08:15   #9  |  Link
kypec
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You better start new thread specific to SOX in Audio encoding section, there are lots of helpful members over there, moderator tebasuna is awesome
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