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Old August 23rd, 2008, 04:34 AM   #1
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Uncompressed -v- AVI

Can someone please tell me if there is a quality difference between the 'avi' and 'uncompressed' render settings, and whether avi is suitable as an intermediate format between Vegas and my compression/conversion tools?

I use Squeeze to batch convert a project I've rendered in Vegas into multiple formats. I also use Windows Media Encoder on occasions because it gives me much greater control over the output.

What I am concerned about, though, is that I am losing a degree of quality by rendering avi from Vegas. Likewise, when I render clips to avi to be used elsewhere in a project, am I introducing generational degradation (now there's a term to be used sparingly!)?

While I'm here, here is a link to a Vegas-only project (except for music creation, done in Cakewalk Sonar) I made for a bit of fun for a client. http://www.dvinfo.net/conf/show-your...atches-up.html

Cheers.

Ian . . .
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Old August 23rd, 2008, 07:15 AM   #2
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Ian,
First I've never noticed any type of loss going to AVI then to MPG. As for uncompressed, they only difference I have seen is the size with uncompressed being about 100million times larger ;-) HOWEVER if I need to preserve the alpha channel for some reason or some other special reason I will render to uncompressed. This happens about once every 100 years for me.
As for quality loss rendering to AVI then to MPG, I have yet to see it and so far frankly no one else has been able to PROVE to me with VISUAL proof there is any loss in quality by using that method which BTW I have been using for years now.

Each section of my VEG gets rendered to AVI then the entire project is rendered to MPG by sections (after I have strung all the AVIs together).
Just the way I do it. I have seen my stuff on a 103 inch TV screen (my sons projection HDTV) and haven't noticed anything I was concerned about as far as generational quality loss. I DID however notice OTHER things I was slightly concerned about on the big screen but thats another post for another time. ;-)

HTHs
Don
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Old August 23rd, 2008, 07:28 AM   #3
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Hi Don,

We have a similar workflow I think. I have to say I have also never noticed any obvious visual degradation, but as my projects get more and more complex, with several nested level of rendered (and sometimes re-rendered) clips I was getting concerned that sooner or later I would hit a problem. (Those are not necessarily nested .veg's, by the way, I'm taking about a string of clips being rendered to an avi, then a string of those avi's being rendered to a further avi etc - just the way it works best for me).

I kind of assumed that because the uncompressed file sizes were SOOO much bigger that there had to be a quality factor involved somewhere.

Thanks for your thoughts on the subject. By the way, I WANT YOUR SON'S TV!

Best,

Ian . . .
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Old August 23rd, 2008, 08:23 AM   #4
 
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First of all, avi is just a wrapper for many different codecs. Asking if there is a difference between avi and uncompressed is like asking if there's a difference between a car and a Ford.Most flavors of avi codecs are some form of compression scheme, and therefore it goes thru some compression. There are lossless codecs and there are lossy codecs.
So, it's rather impossible to answer your question without knowing which avi codec you're referring to. As a personal observation, uncompressed files are huge and unwieldly. I would much prefer a lossless compression codec as an intermediate, with moderate file sizes. The only reason I would consider working with uncompressed would be to transfer to another user or application that doesn't handle one of Vegas' lossless codecs. Cineform, huffyUV, and PICVideo are all good lossless, or very nearly lossless intermediates.
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Old August 23rd, 2008, 08:28 AM   #5
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Quote:
Originally Posted by Bill Ravens View Post
So, it's rather impossible to answer your question without knowing which avi codec you're referring to
Whichever one is used by Vegas!

Thanks for the other info, Bill.
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Old August 23rd, 2008, 08:40 AM   #6
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Hi Ian. FWIW, I render to uncompressed when I need to convert to .flv using Flash Encoder and I notice a disinct difference after the conversion. In my case I am talking short 3-4 minute clips, so the huge file size is not much of an issue. I personally dislike the quality of .flv anyway as opposed to the better appearance of clips done in .wmv so when creating flv clips I find it best to start with highest quality possible.
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Old August 23rd, 2008, 08:42 AM   #7
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Ian, he's right. "AVI" is not a render type. Uncompressed can be in an AVI file. DV can be in an AVI file. Things like DivX can be in an AVI file. But the answer is going to be totally different depending on which one you choose.

Here's a short answer: If you're rendering the timeline to DV-AVI and then rendering that to MPEG2, you can lose some color information. But even then it gets even more muddy because the next question is WHAT ARE YOU STARTING WITH? If you start with DV, render to DV, and then render THAT to MPEG2, the only things affected would be things like titles and still images.

So how about more info:
What type of file are you starting with?
Which AVI preset are you using?
Are you adding things like titles and still images?
etc...
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Old August 23rd, 2008, 09:00 AM   #8
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Thanks Jeff and Edward. So, not as clear cut as all that!

To answer the questions, usually I am:
- Starting with widescreen DV (PAL)
- Using the PAL DV Widescreen DV preset to render
- Yes, almost always adding stills, titles, animations etc.

Of course, giving it some more thought, I realise that the video that comes from my camera is ALREADY compressed - to DV. Does that mean rendering it back to DV will mean no loss of quality and that I can render to DV again and again without problem. Would it then be wise to add titles and stills to the render as late as possible (if that makes sense).
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Old August 23rd, 2008, 09:07 AM   #9
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Yes, starting with DV and rendering to DV will be fine. There's no change with your DV footage. I do that all the time.

However, your stills and titles are a different story. They start with more color information. You then render to the DV color scheme throwing away some color information. Then you render to the MPEG2 color scheme throwing away more color information. So you will lose less color information (one loss instead of two) by going straight to MPEG2 instead of the intermediate DV file in this case.
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Old August 23rd, 2008, 09:18 AM   #10
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Crystal clear. That's sorted out a misunderstanding I've had for a long time. Thanks to alll contributors.
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Old August 23rd, 2008, 04:30 PM   #11
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You could use Lagarith, a free, lossless codec for your intermediate files:

Lagarith Lossless Video Codec
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