do multiple rendered AVI files loose quality ?

will-3 wrote on 3/27/2008, 1:01 PM
When putting a project together from a bunch of clips... one method is to fully produce each clip... adding the effects, titles, etc... then render the clip as an AVI file.

Once all the clips have been rendered... load them onto the time line in the main project and render the whole thing.

the alternate way would be to attempt to render the entire project at once... and if something goes wrong you have to start renddering all over... something you don't want to do in a 30 minute project with more than 50 clips... each with a number of different effects...

Also doing each clip individually keeps the timeline less cluttered.

BUT... rendering to AVI is not lossless... is it? If a clip is rendered one or two times to AVI and then rendered again in the main project... does quality suffer... like resaving a jpeg multiple times... or making a copy of a copy... ???

Or does Vegas see that it is an AVI and then just out the bytes bit by bit without doing a recalculation or whatever?

Thanks for any comments.

Comments

bStro wrote on 3/27/2008, 1:34 PM
Depends on the codec being used. If your source clips are DV, and you render them out to DV without alteration, then the loss is minuscule. Vegas essentially just copies from one place to the other. But use something that has to be encoded like Divx or MPEG, and all bets are off.

That said, if you want the benefit of working in stages but what to avoid multiple renders, then do each section as its own VEG and then nest them all within a master project. There, you can make any final adjustments so that everything matches up.

Rob
rs170a wrote on 3/27/2008, 1:45 PM
I used to do what you're suggesting (render separate segments) before nested vegs came along. Now I save each segment as a separate veg file and then bring all of them into a new project for the master render.
If this isn't an option, render in Best mode as it maintains the 4:4:4 colour space of all photos and generated media.
If you don't do this, a render drops it them to the 4:1:1 colour space that DV has.
Adam Wilt's site has a good explanation of what these numbers mean.
AVI isn't a lossless codec but the one in Vegas is pretty good so, if you're only going down 3 or 4 generations, I wouldn't worry about it.
One last suggestion and that's to use PNG as an image format (change your JPEGs to this) as it's a lossless format as well as being easier for Vegas to handle.

Mike
Former user wrote on 3/27/2008, 1:50 PM
You could use a lossless codec like HUFFYUV.

Dave T2
John_Cline wrote on 3/27/2008, 1:54 PM
If you render sections out to DV, bring them all in, string them together on the timeline and render out the full project to DV, then the loss is not miniscule, it is indeed lossless. Some loss will occur on the first render due to modifications like titling or color correction, these section will have to be recompressed, but any footage which is "untouched" will be smart-rendered and will be identical to the original source footage that came out of the camera. Some other .AVI formats like HuffYUV, Lagarith, MJPEG, DV50 etc, can be smart-rendered. HDV can also be smart-rendered (mostly.)
will-3 wrote on 3/27/2008, 2:38 PM
Well I guess I didn't know about "nested vegs" !!

We are still back on Vegas 5... wonder if it's in that version?

Is their a video tutorial... or written tutorial available?

Or do I just start a project and click file import... or what?

thanks.


Jøran Toresen wrote on 3/27/2008, 3:22 PM
Nested Vegas projects ("nested vegs") were introduced in version 6.

Jøran Toresen
will-3 wrote on 3/27/2008, 3:38 PM
Shucks.

We'll upgrade sometimes this year... but will put-put along with Vegas 5 till then :)
DGates wrote on 3/27/2008, 3:49 PM
I still do the same thing you're talking about. For various projects, I'll edit in sections, render to AVI, then bring those AVI's together for the final AVI. There is NO quality loss. Anybody that says differently is probably a relic from the analog days.

I've tested this myself with up to 10 generations of 10-second video clips with text added to each step in the process (so it's actually creating new video), along with a resolution chart on one side of the screen. The 10th render looks just as good as the first one.
Chienworks wrote on 3/27/2008, 4:14 PM
Not quite true. There is *some* loss with each generation. The difference with SONY 's (SonicFoundry's) DV codec is that it does a very smart job of encoding and seems to be able to recognize what's already DV encoded and maintain it as well as possible. I did a regressive render test out to 99 generations and indeed the 10th generation was almost indistinguishable from the 1st. The 99th generation was still extremely good. By far the most loss occurred in the first generation, far far far more loss than all the following 99 generations combined.

Now, DV codecs aside completely, if you hand Vegas a string of DV files on the timeline and render to DV without any changes such as fades, titles, color corrections, effects, compositing, etc., Vegas won't really render. It will simply copy the frames bit-for-bit into a new file. In this case it is lossless because no rendering is happening. This is a special case though and has nothing to do with how good the codec and rendering engine are. If you make any changes at all then expect another rendering generation to occur and there will be some additional loss, however slight.
DGates wrote on 3/27/2008, 4:24 PM
The point being that any 'loss' is not perceptible, certainly in comparison to analog generational loss.