ffmpeg silently ignores first 50 frames when decoding h264

[Alex Zhukov]

Summary of the bug:

ffmpeg skips first 50 frames in my sample file silent_ignore_44vs94.mp4

expected number of frames 94
actual number of frames 44

it plays as expected (no frames ignored) in all players including vlc, mplayer, quicktime, firefox/safari browser builtin video player, but NOT chrome

Same behavior in ffmpeg 3.2.4, 3.3, and git master

How to reproduce:

% ffmpeg -report -i silent_ignore_44vs94.mp4 -f image2 -y image%04d.jpg
... decode ok ...
Input file #0 (silent_ignore_44vs94.mp4):
  Input stream #0:0 (video): 94 packets read (293495 bytes); 44 frames decoded; 
  Total: 94 packets (293495 bytes) demuxed
...

% ls *.jpg | wc -l
44

I am also attaching the report file and input file

[Alex Zhukov]

input file

[Alex Zhukov]

report log

[Alex Zhukov]

quicktime player plays ok

[Alex Zhukov]

vlc plays ok

[Alex Zhukov]

firefox ok

[Alex Zhukov]

safari ok

[Carl Eugen Hoyos]

How was the input file created?

[Alex Zhukov]

Original stream was encoded with Telestream encoder
Then extracted frames with ffmpeg segmenter

[Carl Eugen Hoyos]

Please provide (the first few MBs of) the Telestream-encoded file.

[Alex Zhukov]

first 2mb of original telestream encoded file

[Alex Zhukov]

Replying to cehoyos:

Please provide (the first few MBs of) the Telestream-encoded file.

attached telestream_first2mb_ticket6335.mp4

[Carl Eugen Hoyos]

Am I correct that for the Telestream file, no frames are missing?

I don't know what you are trying to do but you cannot generally cut files with -vcodec copy and for the first file you uploaded, the reference decoder produces the same output as FFmpeg (meaning any software that outputs different frames has a bug).
Work-around is to use -flags2 +showall which makes decoding (possibly) non-compliant.

[Alex Zhukov]

Replying to cehoyos:

Am I correct that for the Telestream file, no frames are missing?

I don't know what you are trying to do but you cannot generally cut files with -vcodec copy and for the first file you uploaded, the reference decoder produces the same output as FFmpeg (meaning any software that outputs different frames has a bug).
Work-around is to use -flags2 +showall which makes decoding (possibly) non-compliant.

So you are saying the fact that safari, firefox, vlc and quicktime play all frames of this file is a bug in all of them?

[Alex Zhukov]

-flags2 +showall still decodes only 44 out of 94 frames

[Alex Zhukov]

Replying to zhukov:

-flags2 +showall still decodes only 44 out of 94 frames

ffmpeg -flags2 +showall -i silent_ignore_44vs94.mp4 -y -f yuv4mpegpipe silent_ignore_44vs94.y4m decodes 94 frames
ffmpeg -i silent_ignore_44vs94.mp4 -flags2 +showall -y -f yuv4mpegpipe silent_ignore_44vs94.y4m decodes 44 frames

[Carl Eugen Hoyos]

Replying to zhukov:

Replying to cehoyos:

Am I correct that for the Telestream file, no frames are missing?

I don't know what you are trying to do but you cannot generally cut files with -vcodec copy and for the first file you uploaded, the reference decoder produces the same output as FFmpeg (meaning any software that outputs different frames has a bug).
Work-around is to use -flags2 +showall which makes decoding (possibly) non-compliant.

So you are saying the fact that safari, firefox, vlc and quicktime play all frames of this file is a bug in all of them?

I am saying that the H.264 reference decoder does not show the first 50 frames for the sample you uploaded, just as FFmpeg does.

The issue that af1761f7 broke remuxing in certain cases is a duplicate of several other tickets, for example #6227 (and possibly #6275).

$ ffmpeg -i telestream_first2mb_ticket6335.mp4 -vcodec copy out.mp4
ffmpeg version N-85646-g550a9c5 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 6.3.0 (GCC)
  configuration: --enable-gpl
  libavutil      55. 61.100 / 55. 61.100
  libavcodec     57. 93.100 / 57. 93.100
  libavformat    57. 72.101 / 57. 72.101
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 87.100 /  6. 87.100
  libswscale      4.  7.101 /  4.  7.101
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'telestream_first2mb_ticket6335.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42isom
    creation_time   : 2016-01-11T11:30:54.000000Z
  Duration: 00:21:22.70, start: 0.000000, bitrate: 13 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 640x360 [SAR 1:1 DAR 16:9], 914 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
    Metadata:
      handler_name    : Telestream Inc. Dib Library - ReleaseEnterprise 2014.61.142792
      encoder         : AVC
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 93 kb/s (default)
    Metadata:
      handler_name    : Telestream Inc. Dib Library - ReleaseEnterprise 2014.61.142792
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
Output #0, mp4, to 'out.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42isom
    encoder         : Lavf57.72.101
    Stream #0:0(und): Video: h264 (Main) ([33][0][0][0] / 0x0021), yuv420p, 640x360 [SAR 1:1 DAR 16:9], q=2-31, 914 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
    Metadata:
      handler_name    : Telestream Inc. Dib Library - ReleaseEnterprise 2014.61.142792
      encoder         : AVC
    Stream #0:1(eng): Audio: aac (LC) ([64][0][0][0] / 0x0040), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : Telestream Inc. Dib Library - ReleaseEnterprise 2014.61.142792
      encoder         : Lavc57.93.100 aac
frame=  196 fps=0.0 q=-1.0 Lsize=    1137kB time=00:00:09.00 bitrate=1034.2kbits/s speed=29.6x
video:984kB audio:147kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.545792%
[aac @ 0x2c4a760] Qavg: 2458.570

Output file shows less frames than input with FFmpeg (and the reference decoder), not reproducible with -an and -acodec copy.