View Full Version : Question about 'upping' DV footage
July 1st, 2004, 10:05 PM
I've read about a number of workflows that involve rendering footage shot on DV to an uncompressed AVI, BEFORE doing any kind of de-artifacting and colour correction etc. I was wondering what the rationale behind this is?
Clearly, rendering to an 'uncompressed' format doesn't "add" any detail or information that isn't in the DV original so why the extra step? Does the increased colourspace give you more control/lattitude when working with dv originated projects?
In addition, the removal of DV artifacts in footage, what methods do people use for this? There are certain 'de-grainers' about, both as plugins and incorporated into some of the compositors - these appear to be sophisticated and subtle 'blurring' filters. Is this 'softening' the main approach to removing DV compression artifacts? And does this result in a trade off between how much of the artifacts are removed/reduced - and how badly softened your image gets?
Thanks for any help.
July 2nd, 2004, 06:51 AM
What I do, and what I've read that other people do, is to render it out to an uncompressed format (I render to uncompressed AVI) on each pass in post, keeping the compression out of the picture until it is ready to be output to DVD/tape/web video, etc.
I try to do as much pre-comping in AfterEffects as possible to prevent this, as creating several uncompressed AVIs eats up hard drive space quickly. However, I may do color correcting in After Effects, but want to do the basic cuts and edits in Adobe Premiere or Vegas. I would render out uncompressed from After Effects before working on it in the other apps.
What you don't want to do is render each pass out as an MPG, DV AVI, DivX AVI, or any video file that uses compression, as you will degrade the quality each time.
July 2nd, 2004, 11:48 AM
After getting interested in the topic of DV artifacts as discussed in this thread (http://www.dvinfo.net/conf/showthread.php?s=&threadid=28087) I did a little experimentation of my own, the results of which may be found there.
To my surprise I learned that while DV artifacts are of course real, they are much less of a problem than I used to believe. It seems like a much larger problem is the circuitry and small CCD's used in our prosumer cameras. A lot of what I had taken for DV artifacts in the past is actually the result of a noisy image, even under good lighting conditions. I suppose that the problem is compounded when you feed noise to the DV codec which it then compresses. However, if you take a clean JPEG and DV-compress it the results are a lot better than you might think. See my examples in the above-mentioned thread.
So then the problem becomes how does one remove noise from the video images. I have yet to find an effective way to do that. As you say, about all that you can do is blur it in one way or another.
July 3rd, 2004, 06:21 AM
David: most people who do this work with multiple applications.
If you do EVERYTHING inside one application (like Vegas) then
it is of no use.
The idea is to safe on generational loss. Say you capture the
footage, edit it in Vegas or Premiere and then transfer that to
After Effects at bring it back into the NLE for MPEG encoding for
final delivery on DVD.
This construction will yield you at least 3rd generation footage,
fourth generation if you have a bad NLE or let's say "3.5"
generation if you have done transitions and things like that or
fade in's/out's in your NLE.
1) first generation is the capture
2) second generation is output from After Effects
3) third generation is MPEG encoding
If your NLE does not simply cut the files but always re-encodes
you get an extra generation inbetween 1 & 2. If you have done
fade or transitions or any other work besides straight cuts in
your NLE *some* footage will have been re-rendered adding
a ".5" so to speak.
If you used uncompressed from NLE to After Effects and back into
the NLE you will get rid of generation 2 in the list and the .5
(or full generation if you have a bad NLE).
Whether this is "worth" the slower processing and extra diskspace
depends on what you find acceptable. Most people will not be
able to see an extra generation loss and most equipment is not
good enough for that either.
This all "happens" since DV compression is lossy. In other words,
it throws away information to get smaller filesizes.
July 3rd, 2004, 09:29 PM
Thankyou everyone for replying. That's cleared a few things up.
July 12th, 2004, 10:34 AM
Rob, so let me get this straight. If you do all your work in Vegas
there is no advantage to uncompressing it at the beginning
and working with it uncompressed until you go to MPEG?
Might just as well work with it as DV AVI?
July 12th, 2004, 01:31 PM
I was wondering if you were to do your edit in final cut and then export the edit out as an uncompressed 8 bit file.Then bring it into after effects and do color correction... would you then be taking advantage of color correction in the 4:2:2 environment or would it still be the same as 4:1:1. Also if i did this i would output my master to digi beta. So with this method would there be any real quality difference?