[FFmpeg-user] extract first 26 seconds not workings as expected

[Leonardo]

Hello
Carl,

> Please test current FFmpeg git head, if the issue is reproducible
> provide an input sample.

I tested with current git and the results were the same.

As noticed by Moritz at the output of ffprobe 


$ ffprobe part1.mp4 
ffprobe version N-98341-gcca982ee01 Copyright (c) 2007-2020 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --toolchain=hardened --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 55.100 / 56. 55.100
  libavcodec     58. 93.100 / 58. 93.100
  libavformat    58. 47.100 / 58. 47.100
  libavdevice    58. 11.100 / 58. 11.100
  libavfilter     7. 86.100 /  7. 86.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  8.100 /  5.  8.100
  libswresample   3.  8.100 /  3.  8.100
  libpostproc    55.  8.100 / 55.  8.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'part1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.47.100
  Duration: 00:00:13.54, start: 12.666016, bitrate: 316 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1366x768 [SAR 1:1 DAR 683:384], 316 kb/s, 24 fps, 24 tbr, 12288 tbn, 48 tbc (default)
    Metadata:
      handler_name    : VideoHandler


the Duration and the start values are 13.54 and 12.66, respectively.

It looks like that ffmpeg is not respecting "extract from 0 to 26" and instead doing something like

"well, I will start at 12.6 and will stop at 26"

Forcing with -copyinkf as suggested by Moritz, although the extracted part has, indeed, 26 seconds, there is only a "gray screen" from 0 to 12.6 and after that it plays well.

The main.mp4 file plays normal.

Kind regards,
Leonardo

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