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• Adding a color filter at specific intervals in ffmpeg

  9 avril 2015, par JamieL

  I am looking to add the color filter to a rtmp stream in ffmpeg at specific time intervals, say for 10 seconds every 10 seconds. I have tried two approaches. The first :

  -vf "color=#8EABB8@0.9:480x208,select='gte(t,10)*lte(t,20)' [color];[in][color] overlay [out]"

  This streams only the 10 seconds indicated by the select and applies the color filter rather than playing the whole stream and applying the filter to just those 20 seconds.

  I then learnt about split and fifo and tried this approach :

  -vf "[in] split [no-color], fifo, [with-color] overlay [out]; [no-color] fifo, select='gte(t,10)*lte(t,20)' [with-color]"

  I would expect this to play the entire stream, and then select the 10 seconds specified so that I can apply filters, but it does the same as first approach and just plays the 10 seconds selected rather than the entire stream.

  Thanks in advance.

• How with ffmpeg one char with different color ?

  1er juin 2017, par Fatas

  How to ffmpeg one char with different color ?

  I have draw text with ffmpeg, but I can’t find how I can change only one character’s color. All text I can change, but I need one char with a different color.

  I have this part of code :

     ffmpeg -f lavfi \
  
      -i color=c=white:s=1280x720 \
  
      -vf "drawtext=text='aaaaaaaaBaaaaa':\
  
      fontcolor=black:\
  
      fontsize=24:\"
  
      -pix_fmt yuv420p -t 30 -y out.mp4 ");

  But I can’t figure out how need change letter B to red

• application using ffmpeg segfaults because of for loop ?

  6 décembre 2012, par larvyde

  I am writing my first ffmpeg application using the tutorial linked to from the ffmpeg.org documentation page [tutorial] [sample]. Here is my initial code :

  const char * fnmVideoIn = argv [1];
  
  const char * fnmImageOut = argv [2];
  
  
  
  av_register_all ();
  
  
  
  // [] Open the file
  
  AVFormatContext * pcxFormat;
  
  if (avformat_open_input (&pcxFormat, fnmVideoIn, NULL, NULL)) {
  
      fprintf (stderr, "Could not open file %s for reading\n",
  
              fnmVideoIn);
  
      return -1;
  
  }
  
  
  
  // [] Get stream information
  
  if (avformat_find_stream_info (pcxFormat, NULL) < 0) {
  
      fprintf (stderr, "Could not find stream info\n");
  
      return -1;
  
  }
  
  
  
  // [log] print stream info
  
  av_dump_format (pcxFormat, 0, fnmVideoIn, 0);

  and all is well. The program runs without errors and dumps the video info properly. but then I got to the next step...

  ...
  
  // [log] print stream info
  
  av_dump_format (pcxFormat, 0, fnmVideoIn, 0);
  
  
  
  int ixVideoStream = -1, ixStrm;
  
  for (ixStrm = 0; ixStrm < pcxFormat->nb_streams; ++ixStrm) {
  
      if (pcxFormat->streams [ixStrm]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
  
          ixVideoStream = ixStrm;
  
          break;
  
      }
  
  }

  and it exits with a segfault. gdb says :

  (gdb) r test.mp4 out
  
  ...
  
  Program received signal SIGSEGV, Segmentation fault.
  
  0xb7f572c5 in avformat_open_input () from /usr/lib/libavformat.so.53

  how is it possible that avformat_open_input segfaults because of code added after it is called ? I even tested it with a regular i=0 ; i<100 for-loop and it still segfaults ! is this a bug ? For reference, my system is :

  $ gcc --version
  
  gcc (GCC) 4.7.0 20120414 (prerelease)
  
  
  
  $ uname -srvmpio
  
  Linux 3.3.4-1-ARCH #1 SMP PREEMPT Sat Apr 28 06:04:27 UTC 2012 i686 Intel(R) Core(TM)2 Duo CPU P7450 @ 2.13GHz GenuineIntel GNU/Linux
  
  
  
  $ ffmpeg -version
  
  ffmpeg version 0.10.2
  
  built on Mar 17 2012 08:53:01 with gcc 4.6.3
  
  configuration: --prefix=/usr --enable-libmp3lame --enable-libvorbis --enable-libxvid --enable-libx264 --enable-libvpx --enable-libtheora --enable-libgsm --enable-libspeex --enable-postproc --enable-shared --enable-x11grab --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libschroedinger --enable-libopenjpeg --enable-librtmp --enable-libpulse --enable-gpl --enable-version3 --enable-runtime-cpudetect --disable-debug --disable-static
  
  libavutil      51. 35.100 / 51. 35.100
  
  libavcodec     53. 61.100 / 53. 61.100
  
  libavformat    53. 32.100 / 53. 32.100
  
  libavdevice    53.  4.100 / 53.  4.100
  
  libavfilter     2. 61.100 /  2. 61.100
  
  libswscale      2.  1.100 /  2.  1.100
  
  libswresample   0.  6.100 /  0.  6.100
  
  libpostproc    52.  0.100 / 52.  0.100