--- In [email protected], "heytobey" <[EMAIL PROTECTED]> wrote: > > I then opened QT Pro and exported as 'movie to QT movie' > Frame rate =15 > key frame = 5 > > I exported same .avi file in QT Pro but this time I chose: Movie to Mp4 > Frame rate = 30 > keyframe = 24 > > Now this video came out a bit smaller in size but you can see some > sections that have a 'blurriness' to it. > > Tobey >
The number next to "key frame" stands for "create a key frame every [number] frames". In your first video, you made a key frame every 5 out of 15 frames. In the second one, you made one every 24 out of 30 frames. In both cases, "frames" stands for "frames per second", so in the first video, you were making three key frames per second, and in the second one, you were barely making ONE key frame per second. Basically, let's say that key frames are 'definite' frames, and the frames in between them are interpretations from those key frames, and not their own "stand alone" frames. This means that in the first video, you made one key frame and four interpretations, then repeated. In the second video, you made one key frame, then 23 interpretations, then repeated. Video 1:KiiiiKiiiiKiiii every second. Video 2: KiiiiiiiiiiiiiiiiiiiiiiKiiiiii every second. Your H.264 looked "blurry" to you because the computer was 'guessing' at the i-frames instead of creating "stand alone" frames. Also, any time you change scenes in between key frames, the computer's REALLY not going to know what to make of it. Your solution is to decrease the number next to "key frames", which actually _increases_ the number of key frames that you create per second. Also, since you chose 30 frames instead of 15 frames, not only were you making more 'guessing' for the computer by having all those i-frames in a row, but you doubled the amount of frames that the computer had to compress into your data rate. H.264 looks much nicer than Mpeg-4 at the same data rate, so it would have made up for the difference in this case, but if you had used the same codec, you would have been able to see the difference. -- Bill C. http://ems.blip.tv
