Opened 4 years ago

Last modified 2 years ago

#1182 open defect

[ac3] frame sync error

Reported by: carlrosmann Owned by:
Priority: minor Component: undetermined
Version: git-master Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: yes
Analyzed by developer: no

Description (last modified by cehoyos)

seeking in ffplay causes $subject.
Also seeking in another player that uses libav* also causes frame sync error.

I have uploaded file powderblue to

Anything else i can do to help?

Change History (5)

comment:1 Changed 4 years ago by cehoyos

  • Description modified (diff)
  • Priority changed from normal to minor
  • Reproduced by developer set
  • Status changed from new to open
  • Version changed from unspecified to git-master

Not reproducible with ffmpeg.

$ ffplay powderblue.avi
ffplay version N-39664-g6bfb304 Copyright (c) 2003-2012 the FFmpeg developers
  built on Apr 10 2012 01:24:40 with gcc 4.5.3
  configuration: --cc=/usr/local/gcc-4.5.3/bin/gcc --enable-gpl --enable-libtheora --enable-libopenjpeg
  libavutil      51. 46.100 / 51. 46.100
  libavcodec     54. 14.101 / 54. 14.101
  libavformat    54.  3.100 / 54.  3.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 67.101 /  2. 67.101
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0. 10.100 /  0. 10.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, avi, from 'powderblue.avi':
    encoder         : MEncoder version 3.8.5 building on 20100625
  Duration: 01:46:05.10, start: 0.000000, bitrate: 13 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 692x388 [SAR 1:1 DAR 173:97], SAR 794624:794589 DAR 8192:4593, 23.98 tbr, 23.98 tbn, 23.98 tbc
    Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), s16, 448 kb/s
[ac3 @ 0x14f3a00] frame sync error86KB vq=   27KB sq=    0B f=0/0   0/0
  19.82 A-V: -0.325 fd=   0 aq=   95KB vq=    2KB sq=    0B f=0/0

comment:2 follow-up: Changed 2 years ago by gjdfgh

This also happens when seeking in the raw mpeg stream of commercial DVDs (or at least one DVD). After printing this error, the decoder returns an error. This is pretty bad for me, because I think this causes a slight desync.

Looking at the code, I guess it simply fails with AAC_AC3_PARSE_ERROR_SYNC internally. This error also happens when seeking with libdvdread or libdvdnav (in which case seeking with libavformat is not involved at all). This means it fails with the same error in both cases. I'm not sure what to make out of it.

I uploaded a sample named "dvdsample" using, but I'm not really sure where the upload form put it. (Maybe failed?)

comment:3 Changed 2 years ago by gjdfgh

  • Cc added

comment:4 in reply to: ↑ 2 Changed 2 years ago by cehoyos

Replying to gjdfgh:

I uploaded a sample named "dvdsample" using

No such sample was uploaded today, consider reading or upload to

comment:5 Changed 2 years ago by gjdfgh

Retried with a real FTP client. Now it's actually there.

By the way, if you use ffprobe and look at the packet and frame timestamps after a seek, the first audio PTS is different, which implies ffprobe implicitly drops the "bad" first audio packet too. (-read_interval, -show_packets, and -show_frames options.)

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