title: Can you put the result of a blackdetect filter in a textfile using ffmpeg?
body: <p>I'm testing out the "blackdetect" filter in ffmpeg. I want to have the times when the video is black to be read by a script (like actionscript or javascript). I tried:</p>
  
  <pre><code>ffmpeg -i video1.mp4 -vf "blackdetect=d=2:pix_th=0.00" -an -f null -
  </code></pre>
  
  <p>And I get a nice result in the ffmpeg log:</p>
  
  <pre><code>ffmpeg version N-55644-g68b63a3 Copyright (c) 2000-2013 the FFmpeg developers
    built on Aug 19 2013 20:32:00 with gcc 4.7.3 (GCC)
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
  isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
  le-iconv --enable-libass --enable-libbluray --enable-libcaca --enable-libfreetyp
  e --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --ena
  ble-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-l
  ibopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libsp
  eex --enable-libtheora --enable-libtwolame --enable-libvo-aacenc --enable-libvo-
  amrwbenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --
  enable-libxvid --enable-zlib
    libavutil      52. 42.100 / 52. 42.100
    libavcodec     55. 28.100 / 55. 28.100
    libavformat    55. 13.103 / 55. 13.103
    libavdevice    55.  3.100 / 55.  3.100
    libavfilter     3. 82.100 /  3. 82.100
    libswscale      2.  5.100 /  2.  5.100
    libswresample   0. 17.103 /  0. 17.103
    libpostproc    52.  3.100 / 52.  3.100
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video1.mp4':
    Metadata:
      major_brand     : isom
      minor_version   : 512
      compatible_brands: isomiso2avc1mp41
      creation_time   : 1970-01-01 00:00:00
      encoder         : Lavf53.13.0
    Duration: 00:02:01.54, start: 0.000000, bitrate: 275 kb/s
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 768x432 [
  SAR 1:1 DAR 16:9], 211 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc
      Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : VideoHandler
      Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 59
   kb/s
      Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : SoundHandler
  Output #0, null, to 'pipe:':
    Metadata:
      major_brand     : isom
      minor_version   : 512
      compatible_brands: isomiso2avc1mp41
      encoder         : Lavf55.13.103
      Stream #0:0(eng): Video: rawvideo (I420 / 0x30323449), yuv420p, 768x432 [SAR
   1:1 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 25 tbc
      Metadata:
        creation_time   : 1970-01-01 00:00:00
        handler_name    : VideoHandler
  Stream mapping:
    Stream #0:0 -&gt; #0:0 (h264 -&gt; rawvideo)
  Press [q] to stop, [?] for help
  [null @ 00000000003279a0] Encoder did not produce proper pts, making some up.
  [blackdetect @ 0000000004d5e800] black_start:0 black_end:17.08 black_duration:17
  .08
  [blackdetect @ 0000000004d5e800] black_start:62.32 black_end:121.48 black_durati
  on:59.16
  frame= 3038 fps=2317 q=0.0 Lsize=N/A time=00:02:01.52 bitrate=N/A
  video:285kB audio:0kB subtitle:0 global headers:0kB muxing overhead -100.007543%
  </code></pre>
  
  <p>And I'm particularly interested in this part:</p>
  
  <pre><code>[blackdetect @ 0000000004e2e340] black_start:0 black_end:17.08 black_duration:17.08
  [blackdetect @ 0000000004e2e340] black_start:62.32 black_end:121.48 black_duration:59.16
  </code></pre>
  
  <p>So my question:</p>
  
  <ol>
  <li>Is there a way to only take the blackdetect filter output and put it in a .txt file?</li>
  <li>And if this is possible, is there a way to do this in a statement with multiple video inputs? Like in this example</li>
  </ol>
  
  <hr>
  
  <p>example: </p>
  
  <pre><code>ffmpeg -f concat -i mylist.txt -c copy concat.mp4
  </code></pre>
  
  <p>Where mylist.txt is a list of videos:</p>
  
  <pre><code>file 'video1.mp4'
  file 'video2.mp4'
  file 'video3.mp4'
  file 'video4.mp4'
  </code></pre>
  
  <hr>
  
  <p>Basically what I want to have is one or more text files containing information about the black frames in every video in this list to be used by another program</p>