MPEG4 ASP does not seek to keyframe

[Carl Eugen Hoyos]

(issue 2686)

out.png shows artefacts, also reproducible with ffplay.

$ ffmpeg -ss 1 -i q_cut.mp4 -vframes 1 out.png
ffmpeg version N-40924-g349c624 Copyright (c) 2000-2012 the FFmpeg developers
  built on May 21 2012 07:59:42 with gcc 4.3.2
  configuration: --cc=/usr/local/gcc-4.3.2/bin/gcc --enable-gpl --enable-libopenjpeg --enable-libvorbis --enable-libspeex --enable-libmp3lame --enable-libtheora --extra-ldflags=-lm
  libavutil      51. 53.100 / 51. 53.100
  libavcodec     54. 21.101 / 54. 21.101
  libavformat    54.  5.101 / 54.  5.101
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 75.100 /  2. 75.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0. 15.100 /  0. 15.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'q_cut.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf53.0.3
  Duration: 00:00:40.00, start: 0.000000, bitrate: 512 kb/s
    Stream #0:0(und): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p, 1024x1024 [SAR 1:1 DAR 1:1], 1142 kb/s, 5 fps, 5 tbr, 5 tbn, 5 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    : VideoHandler
[buffer @ 0x8f0bbe0] w:1024 h:1024 pixfmt:yuv420p tb:1/5 sar:1/1 sws_param:flags=2
[buffersink @ 0x8f0bec0] No opaque field provided
[format @ 0x8f0c0c0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'format'
[scale @ 0x8f06ec0] w:1024 h:1024 fmt:yuv420p sar:1/1 -> w:1024 h:1024 fmt:rgb24 sar:1/1 flags:0x4
Output #0, image2, to 'out.png':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    creation_time   : 1970-01-01 00:00:00
    encoder         : Lavf54.5.101
    Stream #0:0(und): Video: png, rgb24, 1024x1024 [SAR 1:1 DAR 1:1], q=2-31, 200 kb/s, 90k tbn, 5 tbc
    Metadata:
      creation_time   : 1970-01-01 00:00:00
      handler_name    : VideoHandler
Stream mapping:
  Stream #0:0 -> #0:0 (mpeg4 -> png)
Press [q] to stop, [?] for help
[mpeg4 @ 0x8f12d00] warning: first frame is no keyframe
frame=    1 fps=0.0 q=0.0 Lsize=       0kB time=00:00:00.20 bitrate=   0.0kbits/s
video:262kB audio:0kB global headers:0kB muxing overhead -100.000000%

[Michael Niedermayer]

Is there something that is able to seek reliably to keyframes with this file ? (QT ?)

[Carl Eugen Hoyos]

Seeking seems to work fine in QT with the attached sample - this is not different from ffplay that also seeks fine (only the initial seek is able to produce broken frames and I don't think that can be reproduced with QT).