[FFmpeg-user] Offlist, Is mixing of audio channels happening by default in ffmpeg?

[Nathan Lewis]

On Thu, Aug 1, 2013 at 10:06 AM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> Do you mean the output files are binary identical
> no matter if you use the original line or
> avio_wb24(pb, 0xF);
> ?
>

Sorry, I didn't.  I meant that no matter what line I used the resultant
output files had the same audio configuration with only channel one
enabled.  Channels 2-4 were disabled.  As for the files being binary
identical md5 returns different checksums.


> Alternatively, you could test (unchanged) 454c5d1


 This too results in a file with only channel 1 (QT player "Sound Track 1")
enabled.  Channels 2-4 are disabled.

# ./ffmpeg -i A.mov -c:v copy -c:a copy -map 0:1 -map 0:2 -map 0:3 -map 0:4
-map 0:5 -ss 120 -t 60 -r 30000/1001 C_4545cd1.mov
ffmpeg version 1.1.git-454c5d1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Aug  1 2013 11:30:46 with llvm-gcc 4.2.1 (LLVM build 2336.1.00)
  configuration: --enable-libopenjpeg --enable-nonfree --enable-gpl
--enable-libfaac --enable-libmp3lame --enable-libvpx --enable-pthreads
--enable-libx264 --enable-version3
  libavutil      52. 17.103 / 52. 17.103
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.102 / 54. 63.102
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 41.100 /  3. 41.100
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
Guessed Channel Layout for  Input Stream #0.2 : mono
Guessed Channel Layout for  Input Stream #0.3 : mono
Guessed Channel Layout for  Input Stream #0.4 : mono
Guessed Channel Layout for  Input Stream #0.5 : mono
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'A.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537134592
    compatible_brands: qt
    creation_time   : 2012-10-18 09:59:25
  Duration: 00:25:20.72, start: 0.000000, bitrate: 45253 kb/s
    Stream #0:0(eng): Data: none (tmcd / 0x64636D74)
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:1(eng): Video: prores (apcn / 0x6E637061), yuv422p10le,
720x486, 42159 kb/s, SAR 8:9 DAR 320:243, 29.97 fps, 29.97 tbr, 30k tbn,
30k tbc
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:2(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
s16, 768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:3(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
s16, 768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:4(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
s16, 768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:5(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
s16, 768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:6(eng): Subtitle: eia_608 (c608 / 0x38303663)
Output #0, mov, to 'C_4545cd1.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 537134592
    compatible_brands: qt
    encoder         : Lavf54.63.102
    Stream #0:0(eng): Video: prores (apcn / 0x6E637061), yuv422p10le,
720x486 [SAR 8:9 DAR 320:243], q=2-31, 42159 kb/s, 29.97 fps, 30k tbn,
29.97 tbc
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:1(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:2(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:3(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
768 kb/s
    Metadata:
      timecode        : 01:25:05;00
    Stream #0:4(eng): Audio: pcm_s16be (twos / 0x736F7774), 48000 Hz, mono,
768 kb/s
    Metadata:
      timecode        : 01:25:05;00
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
  Stream #0:2 -> #0:1 (copy)
  Stream #0:3 -> #0:2 (copy)
  Stream #0:4 -> #0:3 (copy)
  Stream #0:5 -> #0:4 (copy)
Press [q] to stop, [?] for help
frame= 1798 fps= 50 q=-1.0 Lsize=  334449kB time=00:01:00.01
bitrate=45653.5kbits/s
video:311882kB audio:22498kB subtitle:0 global headers:0kB muxing overhead
0.020677%