On Thu, 16 Jun 2005, Steven M. Schultz wrote: > On Thu, 16 Jun 2005, Matto Marjanovic wrote: > > > "If mpeg2enc is told to encode N seconds of material with a target > > bitrate of M bits/second... then the resulting file should be > > roughly the N*M bits long, no matter what it is encoding." > > Well - that's not how it read ;) What was written was far too > easy to read as: "that's bits/frame and you don't know what units > you're using".
I was trying to make it clear that since the bit rate is base on time, as long as the source is the same length, in seconds, the output should be the same length. You really didn't need to bite my head off and ignore that what I wrote was a correct explanation of why changing the frame rate without changing the bitrate does not effect the resulting file size. > That has the builtin assumption that all the bits it was given > were being used, right? If it's 'under budget' at 30fps then > reducing the amount of data to be encoded by 20% should result > in being even further 'under budget'. Right? The part that was encoded at 6400 kbits/sec should still be 6400 kbits/sec. The part that was encoded at less, which wasn't much since the average bitrate was 6230, could end up taking 20% less space, since there are 20% fewer frames. But the fields you threw out were the ones which were duplicated by other fields, and so, information wise, you didn't remove anything. I imagine that if you increased your gop length for thr 24 fps encode, so that the number of I-frames per second was the same, the bit rate would increase to be even closer to the 30 fps encode. ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
