Controlling video compression?

  • Nobody/Anonymous


    First I would like to thank you for your application, I'm finding it very useful.  I'm surprised how well it works on my aging PIII 450.

    I noticed that the instructional videos for g/xvidcap you created are about half the size of the ones I create using about the same capture area.  How did you do this?
    I am currently using MS_DIV2 (have to be playable on windows) at 5 frames/sec and your default audio settings. Also, does it matter if I use a .mpg or .avi extension for the filename?

    Thanks in advance,
    Roy P.

    • Karl H. Beckers

      Karl H. Beckers - 2004-08-23

      well, the instructional videos were even recorded at 10 fps.
      There is an image quality preference which has some effect
      on the amount of data you need.
      However, the most important difference you'll be seeing is
      probably the change rate in the area you're capturing. With
      the instructional videos, the greater parts of the screen
      stay the same for most of the time. Since MPEG encoding
      only records the deltas between frames, this makes the
      encoding very efficient for such a case. If you record other
      kinds of action (say: you move a window, use a number of
      menus and the like ... generally change greater portions
      of the captured area) you will get larger videos.



      • Dennis Daniels

        Dennis Daniels - 2004-08-23

        So it would follow that reducing screens to 800*600 and dropping colors down to 1000s would help reduce output size as well... I just made a very small video of 1078*780 (or something like that) no sound, about 8 seconds and it was 400K. Surprisingly large.

        Thanks again though for a great app!


    • Nobody/Anonymous


      I posted the original message in this thread.  After reading Karl's response I reset the quality setting to 50% (I originally though this setting only applied to jpegs).  I also restructured my tutorial movie slightly ie. going directly to side and front views instead of rotating the objects into position.  These changes cut my filesize to where I was only using 2.2Mb for every minute of video with sound.

      Thanks again Karl,
      Roy P.


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