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Unofficial VirtualDub Support Forums > Testing / Bug Reports > Smaller Files With Old Vdub


Posted by: xorvious Mar 10 2003, 11:43 PM
I have been encoding some spongebob episodes to divx and I noticed something strange when I decimate the framerate by 1/2. The files that are created by vdub 1.4d are half the size of a file made with all the same(afaik) settings in 1.4.13 or 1.5.1.
The number of frames is the same and the length of the movie but the datarate in the files created in later version are 2x what the data rate is in 1.4d, it's almost as if it doesnt take the frames out anymore? The files made in the new version are only 10% smaller having only half the frames!
Is this a bug or a "feature" that I didn''t know about? I also tried this with a 20 meg vob file and the SB episodes with both divx and xvid.
Any ideas?
Thanks

Posted by: phaeron Mar 11 2003, 03:18 AM
There might have been some bugs in older versions regarding bitrate control and decimation -- specifically, 1.4d might be telling the codec the wrong framerate, thus causing it to use half the space per frame. If you didn't change the target bitrate when switching decimation on and off, and you aren't saturating the codec one way or the other, then the result is correct: 910kbps is 910kbps regardless of how many frames you are compressing.

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