[FFmpeg-user] ac3 regression since - ac3dec: fix bugs in direct buffer use

[Andy Furniss]

1 meg sample - from a dvd.

http://www.andyqos.ukfsn.org/expoor.ac3

Audio glitches and errors when decoded with current ffmpeg.

First noticed with mplayer, needs -request_channels 2 with ffmpeg.

A different dvd ac3 I happen to have on hd currently is not affected.

bisected to -

7aabeea9ba0e557e834c886de5ea4db8e9a5193d is the first bad commit
commit 7aabeea9ba0e557e834c886de5ea4db8e9a5193d
Author: Michael Niedermayer <michaelni at gmx.at>
Date:   Mon Dec 10 03:11:16 2012 +0100

     ac3dec: fix bugs in direct buffer use.

     This fixes potentially exploitable out of array writes.

     Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

bash-3.2$ /mnt/sdb1/Src/ffmpeg/ffmpeg/ffmpeg -request_channels 2 -i 
expoor.ac3 test.wav
ffmpeg version N-47873-g2b64385 Copyright (c) 2000-2012 the FFmpeg 
developers
   built on Dec 15 2012 20:36:31 with gcc 4.5.1 (GCC)
   configuration: --prefix=/usr --enable-gpl --enable-libx264
   libavutil      52. 12.100 / 52. 12.100
   libavcodec     54. 80.100 / 54. 80.100
   libavformat    54. 49.102 / 54. 49.102
   libavdevice    54.  3.102 / 54.  3.102
   libavfilter     3. 27.101 /  3. 27.101
   libswscale      2.  1.103 /  2.  1.103
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  2.100 / 52.  2.100
[ac3 @ 0xa4fe600] max_analyze_duration 5000000 reached at 5024000
[ac3 @ 0xa4fe600] Estimating duration from bitrate, this may be inaccurate
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, ac3, from 'expoor.ac3':
   Duration: 00:00:18.72, start: 0.000000, bitrate: 448 kb/s
     Stream #0:0: Audio: ac3, 48000 Hz, stereo, fltp, 448 kb/s
Output #0, wav, to 'test.wav':
   Metadata:
     ISFT            : Lavf54.49.102
     Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 
stereo, s16, 1536 kb/s
Stream mapping:
   Stream #0:0 -> #0:0 (ac3 -> pcm_s16le)
Press [q] to stop, [?] for help
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] invalid coupling range (13 >= 3)
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] exponent out-of-range
[ac3 @ 0xa504880] error decoding the audio block
[ac3 @ 0xa504880] incomplete frame
size=    3516kB time=00:00:18.75 bitrate=1536.0kbits/s
video:0kB audio:3516kB subtitle:0 global headers:0kB muxing overhead 
0.002222%