Scrambled Field Order

This happens just enough to make us nuts.

OK, *more* nuts.

We produce DVDs where *some* of the rapid cuts inside of a :30 commercial are clearly out of field order--badly jittering motion--but only on the final DVD.

Nowhere else; Avid, DigiBeta, Capture, Timeline, QuickTime Viewer, View-External Video, External NTSC Monitor does the video look anything other than perfect. 10-bit NTSC uncompressed.

FCP4.5HD and we use QuickTime Conversion to get the VOB files for burning in Studio Pro 2. We don't use Compressor.

The original material was in 24...or 23.98 and we assume 3:2. Some film and some effects, I can check that, but the Avid converted it all to 29.97 before it went to DBeta and then on to us. Our whole world for this job is 29.97. No framerate conversion, no Nattress, no nothing.

Sometimes we export it again and the problem goes away.

Not Tiger yet. Big G5, lots of memory and drives. I can't get to the machine right now to get the accurate numbers. What the frog is happening and/or how do we figure out ahead of time what to look for?

It doesn't always happen and it always seems to know when the client is in a hurry.

Koz

<<The original material was in 24...or 23.98 and we assume 3:2. Some film and some effects, I can check that, but the Avid converted it all to 29.97 before it went to DBeta and then on to us. Our whole world for this job is 29.97.>>

So the DigiBeta you got, post-Avid conversion plays fine on an NTSC monitor from various sources? Not just straight from the deck itself?



- Justin Barham -

Make sure you select lower field for the conversion

Andreas

<<<Make sure you select lower field for the conversion>>>

Yeah. The next step is to rip apart the compression settings. We've had videos where the whole thing was wrong, but the error only showed up on certain clips. For example, if you have 2:2 and 3:2 in the same sequence, a damaged cadence will only show up on the 3:2 video.

I called the producer on an earlier show and he said that certain parts of the transfer looked better faster, so they transferred it at 30 instead of 24. He was right. It looked very very good, but the field sequence change drove us nuts.

That *may* be what's happening here. I have to rip the video apart and find out.

Why would it make any difference? If the show is 29.97 the compressor should be compressing each frame absolutely and then doing the temporal dance to compress interfield motion. Where in the process would it care what the field order was--or why would a compressor need to change it?

Koz

As above, I'm sure now *all* the clips in the sequence are backwards, but it only shows up on the 3:2 or slowed down chunks with the oddball field progression. There's one motion clip where the error only shows up every fifth or sixth frame. I didn't catch that until I put it up on the Beta SP machine.

So now we investigate the export settings when I can get the machine back.

Koz

Don't let Compressor "guess" the field order. Specify it precisely to what it is, lower or upper.

Graeme



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