DVCPROHD to SD DVD Artifacts

Ted Spencer

Veteran
I've been working on a project that involves making an SD DVD out of 30p HD footage I shot on an HVX200a. After editing in FCP7, it looks just fine, and transcodes nicely to an HD or SD Quicktime file for playback on a computer.

But when I use Compressor to transcode to mp2 for a DVD (using the 90 min best quality preset) I am getting periodic incidences of badly pixelated frames that occur exactly 15 frames apart, but only for short, seemingly random stretches of time - perhaps 5 or 10 seconds or so. Then it goes back to normal for several minutes, then recurs similarly for a few seconds. And so on...

This is clearly visble in DVDSP's video display window, while the same spots in the original footage or QT exports look fine.

There was no camera or subject movement...

One thing I'm trying as I type this is another pass through Compressor with it set to Constant bit rate - I found a post elsewhere that implied that this might be the problem. I'll know in a few minutes when it's done.

Otherwise, If anyone has seen this and knows the solution, I'd be very appreciative.
 
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Constant bit rate cured it. Also "built" a lot faster (no surprise) and was basically indistinguishable quality-wise (surprise).

It was wicked-bad before (while it was misbehaving), at the highest possible quality settings. Now, at the lowest, it's just fine. Go figure...
 
What was the length of the video in total minutes, and what was the target and maximum bit rate of the encode that showed artifacting?
 
About 40 minutes, using the default "Best Quality 90 Minutes" settings:

6.2 mbs minimum, 7.4 max

2 pass vbr best

Motion estimation best

It looked fine except when it produced the every-15-frame-degraded issue, which was sporadic.
 
Anything under 90 minutes should be CBR, 7.0mbs, and I always set motion estimation to best.
 
You mean the compression artifacts are created when short programs are set to vbr? And that long ones, set the same way, won't have that problem?

Doesn't seem likely...
 
So...problem solved (for the most part) but I thought I'd bump this puppy up anyway...

Anyone know what's going on with this? Has anyone else encountered it? Could it be specific to DVCPROHD at 30p? I assume lots of others are using DVDSP in max-quality mode(s) to transcode from various kinds of HD footage without seeing this artifact...

Right?
 
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