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• Audio output with video processing with opencv

  22 février 2012, par victor1234

  I am processing video with opencv, but at the same time I need to play audio and simply control it, like loud or current frame number.

  I think I should create a parallel process with ffmpeg, but I don't know how to do so. Can you explain what to do ?

  Or do you know another solution ?

• How to add text to a video with ffmpeg and python

  25 janvier 2013, par Jared Glass

  I've been trying to add text to an avi with ffmpeg and I can't seem to get it right.

  Please help :

  import subprocess
  
  
  
  ffmpeg = "C:\\ffmpeg_10_6_11.exe"
  
  inVid = "C:\\test_in.avi"
  
  outVid = "C:\\test_out.avi"
  
  
  
  proc = subprocess.Popen(ffmpeg + " -i " + inVid + " -vf drawtext=fontfile='arial.ttf'|text='test' -y " + outVid , shell=True, stderr=subprocess.PIPE)
  
  proc.wait()
  
  print proc.stderr.read()

• split video (avi/h264) on keyframe

  30 novembre 2012, par m.sr

  Hallo.

  I have a big video file. ffmpeg, tcprobe and other tool say, it is an h264-stream in an AVI-container.

  Now i'd like to cut out small chunks form the video.

  1. Problem : The index of the video seam corrupted/destroyed. I kind of fixed this via mplayer -forceidx -saveidx <indexfile> <bigvideofile></bigvideofile></indexfile>. The Problem here is, that I'm now stuck with mplayer/mencoder which can use this index file via -loadidx <indexfile></indexfile>. I have tried correcting the index like described in man aviindex (mplayer -frames 0 -saveidx mpidx broken.avi ; aviindex -i mpidx -o tcindex ; avimerge -x tcindex -i broken.avi -o fixed.avi), but this didn't fix my video - meaning that most tools i've tested couldn't search in the video file.

  2. Problem : I cut out parts of the video via following command : mencoder -loadidx in.idx -ss 8578 -endpos 20 -oac faac -ovc x264 -sws 9 -lavfopts format=mp4 -x264encopts <lotsofopts> -of lavf -vf scale=800:-10,harddup in.avi -o out.mp4</lotsofopts>. Now here the problem is, that some videos are corrupted at the beginning. I think this is because the fact, that i do not necessarily cut at keyframe.

  Questions :

  1. What is the best way to fix the index of an avi "inline" so that every tool can again work as expected with it ?

  2. How can i split at the keyframes ? Is there an mencoder-option for this ?

  3. Are Keyframes coming in a frequency ? How to find out this frequency ? (So with a bit of math it should be possible to calculate the next keyframe and cut there)

  4. Is ther perhaps some completely other way to split this movie ? Doing it by hand is no option, i've to cut out 1000+ chunks ...

  Thanks a lot !