wav muxer does not force single stream

[burek]

Summary of the bug:
Trying to extract each channel of the input audio (in 5.1 channel format) into a separate stream of 1 output file, produces invalid output (at least invalid when played with ffplay or vlc).

How to reproduce:

ffmpeg -i 6_Channel_ID.wav -map 0:0 -c:a copy -map 0:0 -c:a copy -map 0:0 -c:a copy -map 0:0 -c:a copy -map 0:0 -c:a copy -map 0:0 -c:a copy -map_channel 0.0.0:0.0 -map_channel 0.0.1:0.1 -map_channel 0.0.2:0.2 -map_channel 0.0.3:0.3 -map_channel 0.0.4:0.4 -map_channel 0.0.5:0.5 out.wav

ffmpeg version N-57781-g0610d6e Copyright (c) 2000-2013 the FFmpeg developers
  built on Nov  1 2013 18:01:35 with gcc 4.8.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfi
g --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopenco
re-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
eex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-li
bvorbis --enable-libvpx --enable-libwavpack --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  libavutil      52. 49.100 / 52. 49.100
  libavcodec     55. 40.101 / 55. 40.101
  libavformat    55. 20.105 / 55. 20.105
  libavdevice    55.  5.100 / 55.  5.100
  libavfilter     3. 90.100 /  3. 90.100
  libswscale      2.  5.101 /  2.  5.101
  libswresample   0. 17.104 /  0. 17.104
  libpostproc    52.  3.100 / 52.  3.100
Input #0, wav, from '6_Channel_ID.wav':
  Duration: 00:00:05.84, bitrate: 4233 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, s16, 4233 kb/s
File 'out.wav' already exists. Overwrite ? [y/N] y
Output #0, wav, to 'out.wav':
  Metadata:
    ISFT            : Lavf55.20.105
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, 4233 kb/s
    Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, 4233 kb/s
    Stream #0:2: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, 4233 kb/s
    Stream #0:3: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, 4233 kb/s
    Stream #0:4: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, 4233 kb/s
    Stream #0:5: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 5.1, 4233 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:0 -> #0:1 (copy)
  Stream #0:0 -> #0:2 (copy)
  Stream #0:0 -> #0:3 (copy)
  Stream #0:0 -> #0:4 (copy)
  Stream #0:0 -> #0:5 (copy)
Press [q] to stop, [?] for help
size=   18099kB time=00:00:05.83 bitrate=25401.7kbits/s
video:0kB audio:18099kB subtitle:0 global headers:0kB muxing overhead 0.000550%

The output file out.wav plays very choppy in ffplay and vlc.

The ​input source file "6_Channel_ID.wav" can be obtained freely from: ​http://www-mmsp.ece.mcgill.ca/Documents../AudioFormats/WAVE/Samples.html

[Cigaes]

WAV files do not support multiple channels. ffmpeg should warn you about it and fail immediately. Instead it merges packets from the additional streams with the first one; patch to fix that sent to the mailing-list.

[burek]

Indeed, you're right. Using out.mkv works perfectly. Thanks!

[Carl Eugen Hoyos]

Reproducible with the following commands:

$ ffmpeg -f s16le -i /dev/zero -t 1 -map 0:0 -map 0:0 out1.wav
$ ffmpeg -i fate-suite/svq3/Vertical400kbit.sorenson3.mov -map 0:1 -map 0:1 out2.wav

[Carl Eugen Hoyos]

Fixed by Nicolas in eeb975f5