Loss of quality on capture

spicyfud

spicyfud

Member
Me and a friend are working on a project using a DVX100a, and capturing with Premiere Pro 2. While on the camera and on playback through the camera on a tv, the footage looks great, but once it's captured with Premiere, the footage takes a SERIOUS loss in quality. The edges of the subjects being shot are pixelated and seem to vibrate; the main portion of the subjects seem somewhat pixelated compared to the original footage. definitely not like the images of people's footage that we've seen on the site. I'm shooting in 24pa, and capturing at the standard 23.98fps. I've tried de-interlacing, interlacing, capturing in abbcd, and 2:3:3:2. We even tried capturing using Windows movie maker(same results). We tried using Sorenson Squeeze to convert the footage to hidef just to see what would happen and well, nothing happened. We're lighting the scenario (a green screen setup) with a professional halogen lighting kit, each bulb 600 watts. Pretty much anything we could try, we tried. Twice. Can someone please shed some light on the subject? Thanks.
 
Are you actually losing resolution once you export, or digital cut to tape, or are your viewer settings on premier just not displaying timeline at 100%?
 
Just a guess... that the codec on Premiere is not handling the color compression well. The difference between playback from tape and playback on the PC is that on capture the image is being recompressed using the local codec. When its played back from tape its got the original compression which is dealing well with the green color. When its played back on Premiere the green is being compressed more, resulting in poor edge quality on the subject.

A couple of ideas that might help at least verify that this is the cause. First, I noticed that the brightness of the background in your sample shot is about the same as the brightness on the subject. Try dropping the background brightness way down while keeping the brightness up on the subject. The difference in luminance might enable better differentiation between the foreground and background in the compression if it is relying on luminance more than color differentiation.

Another idea is to see if you can capture uncompressed. Even if you only get a few seconds before dropping a frame, if you can capture uncompressed and the image quality is good, it might help isolate the source of the problem to the codec rather than anything else.

Good luck!
 
The other thing that you need to remember is that DV is using 4:1:1 color compression. That basically means you have a full resolution monochrome image and the color is overlayed in 2x2 pixel single-color squares. The appearance of full resolution color is essentially an optical illusion caused by the brain's ability to infer the correct color from the luminance. At the edge of the red and green in your image you can see where DV is trying to use a single 4-pixel block of color to represent both red and green. As the subect moves, the dominant color in those blocks at the edge changes, and the color of the block flips, making edge artifacts. This is what makes DV footage an absolute pain to try to key in post. Whenever anything moves, the illusion breaks down, and you get these nasty 4-pixel color artifacts at the boundary.
 
If you search around this forum for chroma sampling and shooting green screen on a DVX you will find that getting a good key from this camera is very difficult. Most will recommend you try shooting your green screen footage on a camera format that uses higher chroma sampling of at least 4:2:2 if not 4:4:4 if you are working a mission-critical project. If you're shooting it to learn (and have fun!) well, you just learned that DV isn't the best for green screen work :)

Also, the color Red is not handled well in DV work at all, which in itself will greatly harm your chances of pulling a clean key from your image. When shooting green screen, it is best to wear a color that will both not allow the green to bleed onto the clothing (like white) and most definatly avoid a vibrant red like your subject is wearing when shooting any DV footage because it will come out looking blocky every time, just like you have found.

I would suggest reading a bit more on this board (it's been covered many times) and on the net for how best to shoot green screen footage in general and on the DVX.
 
Last edited:
spicyfud said:
Here's a screen grab from our test footage. We are mostly concerned with image quality, not the technical aspects of greenscreening (i.e. shadows on background)
<img src="http://i5.photobucket.com/albums/y154/chikanstumpie/test1.jpg">

We checked the preview setting in Premiere, it is not in draft mode.
Click to expand...


That looks like standard DV to me, given the lighting, the contrast between the colors (red on green), etc..

The only other thing I'd say is that when YOU say that you "capture at 23.98," what do you mean by that? Premiere Pro 2.0 doesn't require you to specify a frame rate when you capture, nor do you have to capture in a 24p project. Are you monkeying with settings you don't need to be?
 
I've been reading how some say that using the panasonic dvx100(any model) is not the best solution for green screen and keying in general, however i've seen countless screen grabs that people have shown here using Out of editor programs, not sure of their names, to achieve GREAT looking key's.
 
I wonder who would say something like that? By its nature, progressive footage is ideal for keying (as opposed to interlaced). Any DV camera is bound by the low resolution and 4:1:1 (or 4:2:0) color space of DV, so I'd love to see a technical breakdown of THAT claim.

I've pulled great keys from DVX footage. Like any DV key, it takes some work, but that's the nature of the beast.
 
One of the programs that made dv a pleasure for me to shoot against greenscreening is serious magic's "Ultra" Every shot i got had excelent results of course lighting is crucial as well. In ultra two i must say i was amazed even with "okay" lighting i managed to pull of good grabs. Check out the site www.seriousmagic.com I am very pleased with their products such as dvrack and ultra. When u shoot dv keying is a real pain so i feel this is the only solution.

On another note i have to agree that you lighted ur subjecty and screen the same way. I feel and maybee im wrong but i feel that you shot your subject very close to the screen which is a bigg nono. Try to distance yourself greatly from the screen and light your subject sepretly from the screen. Dam i hope i made sense and it will help u out bro.
 
Andy, we think you are right about Premiere's codec. A friend recommended that we try capturing through Vegas, and there is a big difference. All of our past projects have been in Premiere and we used a GL1, the footage looked pretty good but the DVX looked way worse. So, for now I think we will be switching over to Sony Vegas.

As far as pulling keys, Ultimatte AdvantEdge is an outstanding program. The rendering time may take longer than other plugins but the results are alot cleaner.

Thanks to everyone who replied to our post.
 
Last edited:
Post a pic when you do. While I'm all for someone switching to Vegas, I'm certain the better part of your problem here is bad lighting mixed with DV's low color space and penchant for red.
 
A while ago we posted a question concerning video quality. It ended up we had to capture with Vegas rather than Premiere, with a great improvement in quality. Thanks to all who replied; here's the outcome. This video was shot with a dvx100a, 24p, and a load of After Effects.

Desert Music by Drunken Immortals

http://www.youtube.com/watch?v=pmtUe3qhkz0
 
You must log in or register to reply here.
Back
Top