On Thu, 16 Jun 2005, Steven M. Schultz wrote: > On Wed, 15 Jun 2005, Trent Piepho wrote: > > > On Wed, 15 Jun 2005, Steven M. Schultz wrote: > > > mpeg2enc -D 10 -G 15 -b 6400 -c --dualprime-mpeg2 -E -10 -f 8 -q 2 > > > -K tmpgenc -4 1 -2 1 -o $N.m2v > > > ---------------------- > > > You are specifying a bitrate of 6400 bits per SECOND. Not bits per frame. > > Used mpeg2enc for long?
Yes. > > If you have then you know the '-b' value is in units of kbits/sec > (kbit = 1000). Sorry, I forgot the 'k'. Can you please forgive my typo? > Who said anything about bits/frame? Certainly not I. There were > sizes given but not in any context of bits/frame. > > Where was any mention off bits/frame given? Sure was, from your email. 30fps: -rw-r--r-- 1 sms sms 4106845567 Jun 14 05:29 sinbad-30R0dp.m2v INFO: [mplex] No. Pictures : 158065 INFO: [mplex] No. I Frames : 10538 avg. size 61285 bytes INFO: [mplex] No. P Frames : 147527 avg. size 23460 bytes INFO: [mplex] Average bit-rate : 6229600 bits/sec 24fps: -rw-r--r-- 1 sms sms 4042399041 Jun 15 01:21 sinbad-24R0.m2v INFO: [mplex] No. Pictures : 126450 INFO: [mplex] No. I Frames : 8430 avg. size 65807 bytes INFO: [mplex] No. P Frames : 118020 avg. size 29551 bytes INFO: [mplex] Average bit-rate : 6131600 bits/sec Bytes per frame, bits per frame, kbits per frame, it's the same idea. It was also implied. You seemed to expect that after removing 20% of the frames, the bitrate would go down 20%. That implies average bits per frame should say the same. But that is not how the rate control works, it tries to achieve the specified average bits per second. > The numbers were long term average over the entire encoding - the > average frame SIZES were given for comparision. It's plain to see > there is very little variation no matter what parameters are used > for the encoding or if 20% of the frames are dropped or not. The average number of bits per I frame is 7.3% larger and for P frame it's 26% larger. Overall, the average bits/frame is 23% larger for the 24 fps encode. The number of frames is 20% less. So the bits/second is 1.23 * .80 = 98.4% or 1.6% less for 24fps than 30fps. > > The frames that are dropped are the ones that are the hardest to > encode because they contain mismatched fields (thus the expectation > that compression would be better). You knew that of course and just > forgot it. mpeg2enc should use field based encoding for 3:2 pulldown material. ------------------------------------------------------- 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
