Support G.729 stereo files

[Carl Eugen Hoyos]

​http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/193145
A user uploaded a stereo G.729 file that is currently unsupported.

$ ffmpeg -i g729stereo.wav
ffmpeg version N-72081-gec38a1b Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl
  libavutil      54. 23.101 / 54. 23.101
  libavcodec     56. 38.101 / 56. 38.101
  libavformat    56. 33.101 / 56. 33.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 16.101 /  5. 16.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[g729 @ 0x2897e80] Only mono sound is supported (requested channels: 2).
[wav @ 0x2897460] Failed to open codec in av_find_stream_info
[g729 @ 0x2897e80] Only mono sound is supported (requested channels: 2).
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, wav, from 'g729stereo.wav':
  Duration: 00:00:14.14, bitrate: 8 kb/s
    Stream #0:0: Audio: g729 ([131][0][0][0] / 0x0083), 8000 Hz, 2 channels, 16 kb/s
At least one output file must be specified

[compn]

this file decodes now in mplayer r37400
​http://samples.ffmpeg.org/drivers32/new/G729DecoderDMO.dll

audiocodec g729dmo

info "verint g729"
status working
format 0x83
format 0xA104 ;untested
driver dmo
dll "G729DecoderDMO.dll"
guid 0xe1d97f0c, 0x47d0, 0x416b, 0x97, 0xc6, 0xcd, 0xf5, 0xdc, 0x30, 0xd6, 0xf4

[Carl Eugen Hoyos]

​http://ffmpeg.org/pipermail/ffmpeg-user/2018-August/040972.html
A user provided an additional sample.

[Carl Eugen Hoyos]

Should be fixed in 641d52152f6a6825f2b77b1b4c4cd6621a8fa236