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• Recommendations for real-time pixel-level analysis of television (TV) video

  6 décembre 2011, par Randall Cook

  [Note : This is a rewrite of an earlier question that was considered inappropriate and closed.]

  I need to do some pixel-level analysis of television (TV) video. The exact nature of this analysis is not pertinent, but it basically involves looking at every pixel of every frame of TV video, starting from an MPEG-2 transport stream. The host platform will be server-class, multiprocessor 64-bit Linux machines.

  I need a library that can handle the decoding of the transport stream and present me with the image data in real-time. OpenCV and ffmpeg are two libraries that I am considering for this work. OpenCV is appealing because I have heard it has easy to use APIs and rich image analysis support, but I have no experience using it. I have used ffmpeg in the past for extracting video frame data from files for analysis, but it lacks image analysis support (though Intel's IPP can supplement).

  In addition to general recommendations for approaches to this problem (excluding the actual image analysis), I have some more specific questions that would help me get started :

  1. Are ffmpeg or OpenCV commonly used in industry as a foundation for real-time
     video analysis, or is there something else I should be looking at ?
  2. Can OpenCV decode video frames in real time, and still leave enough
     CPU left over to do nontrivial image analysis, also in real-time ?
  3. Is sufficient to use ffpmeg for MPEG-2 transport stream decoding, or
     is it preferable to just use an MPEG-2 decoding library directly (and if so, which one) ?
  4. Are there particular pixel formats for the output frames that ffmpeg
     or OpenCV is particularly efficient at producing (like RGB, YUV, or YUV422, etc) ?

• ffmpeg : How to use blackdetect filter and cut black frames at once

  25 juin 2012, par cache

  I use the following command to detect black screen interval :

  " ffmpeg -i black.mp4 -vf blackdetect=d=1:pic_th=0.70:pix_th=0.10 -an -f null "

  and it gives me output containing this line :
  "[blackdetect @ 0x219a580] black_start:0 black_end:1.44 black_duration:1.44"

  Now I want to cut off black screens in the video from 0-1.44s.

  So my question is : How to use blackdetect filter and cut black frames at once

  Thanks !

• Ffprobe with print json doesn't print anything

  10 septembre 2012, par Richard Knop

  I am trying to get information about a movie (resolution, frame rate, bit rate, codecs, duration etc) in a human readable way. I found this commnad :

  ffprobe -v quiet -print_format json -show_format -show_streams somefile.asf

  In this Stack Overflow question : Get ffmpeg information in friendly way

  But it doesn't work for me. When I try it in a terminal, the output is empty :

  richard@richard-desktop:~/projects/hello-python$ ffprobe -v quiet -print_format json -show_format -show_streams tests/test_1.mpg 
  
  richard@richard-desktop:~/projects/hello-python$