Slow counter / incorrect duration for aac-in-flv

[Carl Eugen Hoyos]

(videolan ticket 8195)
I will upload an audio-only flv sample that can be decoded but the shown duration is wrong, both the duration shown before decoding and the duration shown after decoding.
The time counter is wrong for both ffplay and MPlayer, seeking works fine with MPlayer, fails with ffplay.

$ ffmpeg -i sky_the80s_aacplus.flv out.wav
ffmpeg version N-50086-gd41efc1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Feb 19 2013 09:36:55 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --disable-indev=jack
  libavutil      52. 17.102 / 52. 17.102
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.100 / 54. 63.100
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 38.103 /  3. 38.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[flv @ 0x32bdfc0] max_analyze_duration 5000000 reached at 5014000 microseconds
Input #0, flv, from 'sky_the80s_aacplus.flv':
  Duration: 00:01:08.77, start: 0.000000, bitrate: 74 kb/s
    Stream #0:0: Audio: aac, 44100 Hz, stereo, fltp
Output #0, wav, to 'out.wav':
  Metadata:
    ISFT            : Lavf54.63.100
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (aac -> pcm_s16le)
Press [q] to stop, [?] for help
[flv @ 0x32bdfc0] Stream discovered after head already parsed
[flv @ 0x32bdfc0] New data stream 0:1 at pos:254270 and DTS:27.274s
size=   21168kB time=00:01:08.81 bitrate=2519.9kbits/s
video:0kB audio:21168kB subtitle:0 global headers:0kB muxing overhead 0.000369%

Duration and time claim that the sample is ~68 seconds, but it actually is over two minutes long:

$ ffmpeg -i out.wav -f null -
ffmpeg version N-50086-gd41efc1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Feb 19 2013 09:36:55 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --disable-indev=jack
  libavutil      52. 17.102 / 52. 17.102
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.100 / 54. 63.100
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 38.103 /  3. 38.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[wav @ 0x1c49fc0] max_analyze_duration 5000000 reached at 5015510 microseconds
Guessed Channel Layout for  Input Stream #0.0 : stereo
Input #0, wav, from 'out.wav':
  Metadata:
    encoder         : Lavf54.63.100
  Duration: 00:02:02.88, bitrate: 1411 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf54.63.100
    Stream #0:0: Audio: pcm_s16le, 44100 Hz, stereo, s16, 1411 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le -> pcm_s16le)
Press [q] to stop, [?] for help
size=N/A time=00:02:02.88 bitrate=N/A
video:0kB audio:21168kB subtitle:0 global headers:0kB muxing overhead -100.000101%

The same can be shown with ffplay:

$ time ffplay sky_the80s_aacplus.flv
ffplay version N-50086-gd41efc1 Copyright (c) 2003-2013 the FFmpeg developers
  built on Feb 19 2013 09:36:55 with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl --disable-indev=jack
  libavutil      52. 17.102 / 52. 17.102
  libavcodec     54. 92.100 / 54. 92.100
  libavformat    54. 63.100 / 54. 63.100
  libavdevice    54.  3.103 / 54.  3.103
  libavfilter     3. 38.103 /  3. 38.103
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
[flv @ 0x7f7d6c0008c0] max_analyze_duration 5000000 reached at 5014000 microseconds
Input #0, flv, from 'sky_the80s_aacplus.flv':
  Duration: 00:01:08.77, start: 0.000000, bitrate: 74 kb/s
    Stream #0:0: Audio: aac, 44100 Hz, stereo, fltp
  23.20 A-V:  0.000 fd=   0 aq=    1KB vq=    0KB sq=    0B f=0/0

real    0m43.481s
user    0m0.937s
sys     0m0.474s

[Michael Niedermayer]

Is it known what generated this file ?
Iam asking as it does not look like a valid flv file

[Carl Eugen Hoyos]

jb opened the original ticket, maybe he knows the answer.

[Carl Eugen Hoyos]

He doesn't know:
​http://trac.videolan.org/vlc/ticket/8195#comment:3