Auto-detection of Sonic Foundry Soft Encode AC3 files with a 16-byte header fails

[cehoyos]

(issue 2647)
Attached sample can be decoded with a52dec -o wav6 (shows many lines of "skip"), but auto-detection fails completely with FFmpeg, MPlayer, xine and vlc.

It was produced with Sonic Foundry Soft Encode and every frame starts with a 16-byte header (possibly with timestamps).

$ ffmpeg -i sonic.ac3
FFmpeg version git-N-27832-g424ffee, Copyright (c) 2000-2011 the FFmpeg developers

built on Mar 7 2011 23:17:15 with gcc 4.5.2
configuration: --cc=/usr/local/gcc-4.5.2/bin/gcc --enable-gpl
libavutil 50. 39. 0 / 50. 39. 0
libavcodec 52.113. 2 / 52.113. 2
libavformat 52.102. 0 / 52.102. 0
libavdevice 52. 2. 3 / 52. 2. 3
libavfilter 1. 76. 0 / 1. 76. 0
libswscale 0. 12. 0 / 0. 12. 0

sonic.ac3: Invalid data found when processing input

$ ffmpeg -f ac3 -i sonic.ac3 out.wav
FFmpeg version git-N-27832-g424ffee, Copyright (c) 2000-2011 the FFmpeg developers

built on Mar 7 2011 23:17:15 with gcc 4.5.2
configuration: --cc=/usr/local/gcc-4.5.2/bin/gcc --enable-gpl
libavutil 50. 39. 0 / 50. 39. 0
libavcodec 52.113. 2 / 52.113. 2
libavformat 52.102. 0 / 52.102. 0
libavdevice 52. 2. 3 / 52. 2. 3
libavfilter 1. 76. 0 / 1. 76. 0
libswscale 0. 12. 0 / 0. 12. 0

[ac3 @ 0x11e4650] max_analyze_duration reached
[ac3 @ 0x11e4650] Estimating duration from bitrate, this may be inaccurate
Input #0, ac3, from 'sonic.ac3':

Duration: 00:00:37.44, bitrate: 447 kb/s

Stream #0.0: Audio: ac3, 48000 Hz, 5.1, s16, 448 kb/s

Output #0, wav, to 'out.wav':

Metadata:

encoder : Lavf52.102.0
Stream #0.0: Audio: pcm_s16le, 48000 Hz, 5.1, s16, 4608 kb/s

Stream mapping:

Stream #0.0 -> #0.0

Press [q] to stop encoding
[ac3 @ 0x11ef090] frame sync error
Error while decoding stream #0.0
Error while decoding stream #0.0

...

Error while decoding stream #0.0imes
Error while decoding stream #0.0imes

Last message repeated 1159 times

[ac3 @ 0x11ef090] incomplete frame
size= 20880kB time=37.12 bitrate=4608.0kbits/s
video:0kB audio:20880kB global headers:0kB muxing overhead 0.000318%

out.wav plays fine.

[michael]

without looking at the file this sounds like a small demuxer should be added that removes these 16byte headers

[michael]

ac3 probe changed to detect this.