V7a "Insert I-frames at markers" doesn't.

john-beale wrote on 9/15/2006, 4:46 PM

I upgraded from V6d to V7.0a mostly based on the ability to specify I-frames exactly for precise chapter starts. Ok, the option is there in the video tab of the MainConcept MPEG2 render menu, but it doesn't work.

As my first Vegas 7 test, I put a marker on the timeline at frame 24 of a short selection, checked "Insert I-frames at markers" and rendered, but viewing the resulting MPEG2 file in VirtualDub I see that the I-frames are at 0, 15 and 30 just as always (15-frame GOP). Frame 24 is a P frame. I opened the mpeg file with DVDA 4 and confirmed the I-frame placement is not as I had selected. I tried with this with both VBR and CBR type MPEG files. Neither one worked.

Does I-frame selection work for anyone? What's the trick?

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ScottW wrote on 9/19/2006, 7:21 AM

Ed, fwiw, I found part of the issue with DVD Lab and frame numbers. One the display that DVD Lab is showing, it's showing the frame number in its coded position, not in the presentation position.

I've found a number of instances in my testing where the MC encoder is starting a GOP with the BBI sequence in coded order but the presentation order is IBB. And of course, the deal you found with the first GOP being IBB coded and BBI presentation.

--Scott

ECB wrote on 9/19/2006, 8:03 AM

Scott, presentation vs coded order is why I believe folks have trouble with chapter points in DLP. With the BBI coded order not all players recognize the frames ahead of the I frame and discard them. Qtime, for example, tosses the leading B frames. My test mpeg with numbered frames encoded with closed GOPs with V6 when played with QTime starts with frame 3 skipping frames 1 and 2, the leading B frames. The BBI coded order is fine but not all DVD players are implemented to spec. :)

Ed