pixelation

S

sbc

New member
I'm editing a multicamera shoot right now. I had three other cameras and one DVX100 in the mix. The footage all looks fine except the stuff from the DVX100 which is very pixelated -- especially in lower light.

I'm viewing the footage and capturing to FCP with a Canon GL1. I tried exported the footage at DVD quality and it looks awful. I tried re-capturing it but it's still pixelated. Does anyone know what's going on? Sample picture is linked so you can see the pixelation

sample image of the problem

And of course I realize that sample image isn't in focus, but it was a good example of the pixelation that's happening
 
Definitely the image suffers from color subsampling native to miniDV, but even this looks extreme, like it's in a low-quality preview mode or something. Can you post a grab from the other cameras to compare? It could just be the DVX saturation making the problem look worse.

The DV Rebel's Guide has a great no-cost color smoothing/deartifacting technique, if you have After Effects.
 
the other cameras look just fine. The screen grab is not a preview - it looks like that even when the DV deck is playing the tape. I exported a clip in mpeg-2 DVD quality just to be sure and I get the same artifacting. The problem isn't as bad when the lights come up more, but the darker shots are awful.

I'm not sure what settings the camera operator had -- I just asked him to make sure it was 4:3, 60i

Unfortunately I don't have after effects -- just working with FCP (But I do have some Magic Bullet filters and it looks like the 4:1:1 deartifacting filter might be what I need. Goin to mess around with that today.
 
If FCP has a "Chroma Blur" filter, apply a blur to the horizontal pixels. It'll really help the problem.
 
I think I'm having the same problem as sbc, though not as extreme. here is a frame grab:

frame.jpg


this was shot in 24p, shutter 1/48, and imported into FCP at standard NTSC settings.

does the pixelation have anything to do with the great lighting difference between the subject and the background, or with the background being black? i only say it because i have never seen this before, and i have shot bright colors on DVX many times. how to avoid this problem in the future? would anyone suggest changing some setting in the scene file?

if there is any interest on elaborating on some of the remedies suggested in this thread I would be very happy to hear it. Has anyone successfully gotten rid of the pixelation with filters or other tools? Please let me know

thanks

serge
 
might the exaggerated effect from my shot be from boosting the gain too much? Maybe the camera op was using a higher than normal shutter speed or something.
 
Well, it may be a problem to you guys, but it's actually completely to be expected based on the DV format. If you want better results in those conditions, you need to switch to something like DVCPRO 50 format, which stores twice as much color information. As it is, it won't be as bad on playback as it looks on capture.

FCP has Chroma Smoother, Nattress tools has G Nicer, Magic Buller has Deartifact, and the DV Rebel's Guide gives you a free and very high quality method that involves After Effects. If you smooth this out, you need to render to a format that can hold that extra detail. If you render back to DV, the blockines will just reappear. When you render out to DVD, it will also reappear. MPEG-2 uses 4:2:0 color sampling, just like PAL DV. This sort of goes with the territory.
 
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Joshua Provost said:
If you render back to DV, the blockines will just reappear. When you render out to DVD, it will also reappear. MPEG-2 uses 4:2:0 color sampling, just like PAL DV.
Click to expand...

Doing very cursory reading on the issue I found something about I-frame only MPEG-2, which uses 4:2:2 compression. Is this an available option in Compressor or in any other compression mechanism one could get hold of? And then, can this go onto a DVD, or will a DVD-authoring program still convert the file into regular MPEG-2 in order to burn it?

s
 
If you're trying to make a DVD that will play in a regular DVD player, then it must always be converted to 4:2:0 MPEG-2. That's the video format that DVD players can play.

If you're making a data DVD, then you can put any type of file on it, with the understanding that it won't be playable on any set-top DVD player (it'd only be usable from a computer DVD-ROM).

If you're making a video DVD, it's gonna get recorded as 4:2:0 MPEG-2, always. That's what DVDs are.
 
If you smooth the chroma there is a way. Try adding a little noise to the wash areas before outputting it back to DV and *some* of the blockiness will be reduced.
 
this might not be it but with one of the dvx's i used it would always reset itself to record in LP instead of SP and that will create pixalization.
 
Joshua Provost said:
Well, it may be a problem to you guys, but it's actually completely to be expected based on the DV format. If you want better results in those conditions, you need to switch to something like DVCPRO 50 format, which stores twice as much color information. As it is, it won't be as bad on playback as it looks on capture.
Click to expand...
I've seen this response after searching through old threads a bit. I don't buy it. My other cameras were shooting in DV, and they didn't have this problem. I've done a lot of shooting on 3-chip, consumer-grade Sony and Canon cameras and have not encountered a problem close to as bad as this.
 
Maybe the guy had the chroma levels in camera too high. It shouldnt be like that and you can see in the area that is on the right near those little lights its not happening.
 
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