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• How to programatically generate video of a number or countdown

  27 novembre 2013, par xorsyst

  I've got some python that drives ffmpeg to convert some videos and do other processing. I'd like to prepend the videos with a couple of seconds of a number, and append a short countdown timer video.

  Each video could have different values for the numbers and length of countdown. Is there an easy programatic way to generate this sort of video ? I was thinking of perhaps coding some wxpython to generate the required stuff, but how to save that out as a video file or stream it to ffmpeg ?

  Ideas welcome - doesn't have to involve Python, external programs (Windows) are ok.

• JavaCV FFmpegFrameRecorder properties explanation needed

  29 décembre 2014, par Leron

  I’m using FFmpegFrameRecorder to get the video input from my webcam and record it into a video file. The problem is that I’m building my application using a few different demo source codes that I found and I use properties some of which are not completely clear to me.

  First, here is my code snippet :

  FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(FILENAME,  grabber.getImageWidth(),grabber.getImageHeight());
  
  
  
          recorder.setVideoCodec(13);
  
          recorder.setFormat("mp4");
  
          recorder.setPixelFormat(avutil.PIX_FMT_YUV420P);
  
          recorder.setFrameRate(30);
  
          recorder.setVideoBitrate(10 * 1024 * 1024);
  
  
  
          recorder.start();

  • setVideoCodec(13) - What is the meaning of this (13) how can I understand what actual codec stands behind any number ?
  • setPixelFormat - Just get this, don’t know what it’s doing in general
  • setFrameRate(30) - I think this should be pretty clear but still what is the logic behind what frame rate we choose (isn’t the high the better ?)
  • setVideoBitrate(10*1024*1024) - again almost no idea what this does and what’s the logic behind the numbers ?

  At the end I just want to mention one last problem that I get recording video like this. If the actual length of the video is let’s say 20secs. When I play the video file created from the program it runs significantly faster. Can’t tell if it’s exactly 2 times faster than it should be but in general if I record a 20sec video then it’s played for about 10secs. What may cause this and how can I fix it ?

• ffmpeg not using wildcard properly from batch script

  20 mars 2013, par Paul Green

  What I want to do is actually super simple and is working just fine if executed from within the cmd window, though it does not work when used within a batch script. The following command would normally get all .png files with the pattern anim_xxxx.png (%04d stands for 4 numbers in ffmpeg).

  ffmpeg -f image2 -i anim_%04d.png -vcodec mjpeg -q:v 0 -r 25 foo.avi

  Now the error I get is with the wildcard for my image sequence and I have no clue what the problem is. Using another wildcard like * gives me the same error.

  [image2 @ 000000000033e8c0] Could find no file with with path
  'anim_render.bat4d.png' and index in the range 0-4
  anim_render.bat4d.png : No such file or directory

  does %04d resemble any variable in a batch file that does not exist outside of batch files ? I could not find any similar cases so far.