low bitrate issues

megatronman wrote on 4/17/2003, 2:36 PM

I'm encoding some animation and putting it on DVD-r with the eventual goal of getting the DVD pressed. Now, most of the time it works fine, but some of the simpler animated sections get compressed down to almost nothing by the MPEG encoder, and they'll skip on playback on some set-top players. Even when I set the VBR encoding minimum bitrate up higher, it still wants to compress this animated stuff down to below 1 Mbit/s. My question is, can I feel safe that these occasional bitrate dips will be fine on a pressed DVD? Or should I keep encoding until I don't get the dips?

Comments

craftech wrote on 4/17/2003, 4:19 PM

Keep encoding until you don't get the dips. They won't just "disappear". Try encoding at a CBR.

megatronman wrote on 4/17/2003, 5:04 PM

But then, I've gotta ask, why does the DVD stream preset on the Vegas MC encoder have a 192,000 minimum bitrate? That seems woefully low if low bit rates during fade-ins and animations on DVDs are a problem.

craftech wrote on 4/17/2003, 7:06 PM

Because it won't encode at all below that.

mikkie wrote on 4/18/2003, 9:05 AM

FWIW, whether you're using winmedia, real, or mpeg 1/2, the encoder tries to eliminate what it considers the most irrelevant data. As suggested earlier, a constant bitrate does help, & so does raising the average and minimum bitrates. You might want to also try increasing the number of keyframes, in mpeg2 possibly varying the number non I frames. If none of that cures your problem, might try changing the mpeg2 encoder settings themselves, from motion estimation to matrix settings. As a last resort, adding small bits of background motion or even noise can force the encoder to keep more of the original frame.