On Thu, 3 Jan 2002, Stephen Davies wrote: > > I've noticed an odd effect - I use a rate of 2500 for video, which gives a > fairly good video quality. But I'm finding that suddenly FFMPEGrec will > turn down the bit rate dramatically - I'd guess from 2500 down to 400 or > less. As you might expect, that gives a very poor picture. Found and fixed the bug (in ffmpeg). The bug was an integer overflow whilst ffmpeg was calculating the right "q" to use to meet the bitrate budget. It happens when you've asked for a higher bit rate than is necessary to meet ffmpeg's "perfect" q setting (which is q=3) I posted a patch to the ffmpeg mailing list. A workaround is to keep -vb bitrate low enough to constrain the q at 3 or worse. (IE, something like 1400-1600kbps for 352x288 resolution, 3500-4500 for 720x576) Regards, Steve
