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• How to stop holding the last frame in video stream as part of an mp4 container encoded with ffmpeg ?

  13 mars 2019, par maximedupre

  I’m encoding a dummy mp3 file (7 seconds of white noise) and a dummy mp4 file (silent with a red background image for 4 seconds) together to form a mp4 file. The command to generate this file is :

  ffmpeg -i dummy.mp3 -itsoffset 0 -t 2 -ss 0 -i dummy.mp4 -c:v copy -map 1:v -map 0:a -copyts output.mp4 

  So as you can see, I truncate dummy.mp4 to 2 seconds (originally 4 seconds). However, when I play output.mp4 in QuickTime Player, I see the red background image for the whole 7 seconds.

  What I want is the dummy.mp4’s red background image for 2 seconds, then black (nothing).

  How can I achieve this ?

  Cheers !

• How to stop perl buffering ffmpeg output

  4 février 2017, par Sebastian King

  I am trying to have a Perl program process the output of an ffmpeg encode, however my test program only seems to receive the output of ffmpeg in periodic chunks, thus I am assuming there is some sort of buffering going on. How can I make it process it in real-time ?

  My test program (the tr command is there because I thought maybe ffmpeg’s carriage returns were causing perl to see one big long line or something) :

  #!/usr/bin/perl
  
  
  
  $i = "test.mkv"; # big file, long encode time
  
  $o = "test.mp4";
  
  
  
  open(F, "-|", "ffmpeg -y -i '$i' '$o' 2>&1 | tr '\r' '\n'")
  
          or die "oh no";
  
  
  
  while(<f>) {
  
          print "A12345: $_"; # some random text so i know the output was processed in perl
  
  }
  
  </f>

  Everything works fine when I replace the ffmpeg command with this script :

  #!/bin/bash
  
  
  
  echo "hello";
  
  
  
  for i in `seq 1 10`; do
  
          sleep 1;
  
          echo "hello $i";
  
  done
  
  
  
  echo "bye";

  When using the above script I see the output each second as it happens. With ffmpeg it is some 5-10 seconds or so until it outputs and will output sometimes 100 lines each output.

  I have tried using the program unbuffer ahead of ffmpeg in the command call but it seems to have no effect. Is it perhaps the 2>&1 that might be buffering ?
  Any help is much appreciated.

  If you are unfamiliar with ffmpeg’s output, it outputs a bunch of file information and stuff to STDOUT and then during encoding it outputs lines like

  frame=  332 fps= 93 q=28.0 size=     528kB time=00:00:13.33 bitrate= 324.2kbits/s speed=3.75x

  which begin with carriage returns instead of new lines (hence tr) on STDERR (hence 2>&1).

• Stop hardcoding align=32 in av_frame_get_buffer() calls.

  8 février 2017, par Anton Khirnov

  Stop hardcoding align=32 in av_frame_get_buffer() calls.
  Use 0, which selects the alignment automatically.
  

  • [DH] doc/examples/encode_video.c
  • [DH] doc/examples/muxing.c
  • [DH] doc/examples/vaapi_encode.c
  • [DH] fftools/ffmpeg.c
  • [DH] fftools/ffmpeg_videotoolbox.c
  • [DH] libavcodec/asvenc.c
  • [DH] libavcodec/encode.c
  • [DH] libavcodec/libwebpenc_common.c
  • [DH] libavcodec/mpegvideo_enc.c
  • [DH] libavcodec/pngenc.c
  • [DH] libavcodec/tdsc.c
  • [DH] libavfilter/af_compand.c
  • [DH] libavfilter/af_compensationdelay.c
  • [DH] libavfilter/avf_showcqt.c
  • [DH] libavfilter/vf_find_rect.c
  • [DH] libavfilter/vf_signalstats.c
  • [DH] libavutil/frame.c
  • [DH] libavutil/hwcontext.c
  • [DH] libavutil/hwcontext_qsv.c
  • [DH] tests/api/api-flac-test.c
  • [DH] tests/api/api-threadmessage-test.c