Incorrect duration when decoding raw G.729

[Carl Eugen Hoyos]

$ ffmpeg -i fate-suite/act/REC03.act -acodec copy -map 0:0 -f rawvideo out.g729

$ ffmpeg -i out.g729 out.wav
ffmpeg version N-80026-g936751b Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 42.100 / 57. 42.100
  libavformat    57. 37.100 / 57. 37.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 45.100 /  6. 45.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[g729 @ 0x2dc93a0] Estimating duration from bitrate, this may be inaccurate
Guessed Channel Layout for  Input Stream #0.0 : mono
Input #0, g729, from 'out.g729':
  Duration: 00:01:05.79, start: 0.000000, bitrate: 8 kb/s
    Stream #0:0: Audio: g729, 8000 Hz, 1 channels, s16
[wav @ 0x2dcbf40] Using AVStream.codec to pass codec parameters to muxers is deprecated, use AVStream.codecpar instead.
Output #0, wav, to 'out.wav':
  Metadata:
    ISFT            : Lavf57.37.100
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 8000 Hz, mono, s16, 128 kb/s
    Metadata:
      encoder         : Lavc57.42.100 pcm_s16le
Stream mapping:
  Stream #0:0 -> #0:0 (g729 (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
size=    1028kB time=00:00:00.83 bitrate=10119.2kbits/s speed=6.01x
video:0kB audio:1028kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.007410%

Both input and output file have a duration of 65 seconds.

[Carl Eugen Hoyos]

Fixed by Paul in 35a12d2071efa5c408e6dd4a4a6d0cf930fb3eb3