Prerendering an Uncompressed AVI - PROBLEM!

Jonathan Neal wrote on 9/4/2005, 1:41 AM
Hello again,

I have been experiencing an ongoing problem in Vegas 6 when prerendering my video as an uncompressed AVI file and then rendering the final product. I have included an example of my problem at the end.

When working on a large project, it's useful to pre-render portions of the video that will not be touched later, this way I never have to render those portions again. However, when prerendering in an uncompressed AVI format, the Render feature will ignore my prerendered strips. I would plead that if this is a bug, it be fixed. If not, then I would plead that my error be explained by someone genorous here. I'm really very surprised that I could not find this problem addressed on the forums, even if I'm missing something obvious.

You can try this yourself.

First, I start a project with these settings:
Width: 655
Height: 480
Field order: None (progressive scan)
Pixel Aspect Ratio: 1.000 (Square)
Frame rate: 29.970 (NTSC)

I leave everything else as it is.

Then, for this particular experiment, I create a video layer and place a 20 second clip of Text Media "Sample Text". Then, I add one Video Event FX, it can be anything, for this expirement I add Film Grain. The point of this is to create a track that would be useful to pre-prerender if working on other events in the timeline.

Now, SHIFT+M, because its time to prerender! Select Custom, and use the following entries.

Frame size: (Use project settings), or you can even specify
Frame rate: 29.970 (NTSC)
Field order: Progressive Scan
Pixel aspect ratio: 1.0000
Video format: Uncompressed

I leave everything else as it is. I even save this template for my later use in RENDER (just incase).

After the video is prerendered, everything seems to be just as it should be. Now, goto File -> Render As, and use the exact settings you did for your prerendering. I saved a template earlier in prerendering so I just use that. Now save your project.

You will sit through the rendering process again! Here is my example .VEG file.

http://www.turboultra.com/hornet/vegas_prerender_bug.veg


I would appreciate any feedback, even just an 'i tried it' and results from another user. Thanks everyone.

Comments

farss wrote on 9/4/2005, 3:58 AM
Don't use prerendering much and I think from memory prerenders are only temporary, it's very easy for Vegas to decide the prerender file is no longer valid, even if all you cahnge is further down the T/L than the portion you've prerendered.
Better way to work, render to new file and when done bring the bits into a master project, that'll avoid the problem for sure.
Bob.
Jonathan Neal wrote on 9/4/2005, 5:20 AM
In the example I just posted I don't do anything after I prerender the file.

When I SHIFT+M and prerender, an AVI file is created in the "\Application Data\Sony\Vegas\6.0" folder, and that is essentially my "rendered" file. Also, In my example I don't do ANYTHING between the time I prerender and render; that has to speak for something, right?

I really want to thank you for such a speedy reply, but I would also note that if I were to follow that advice I would be wasting my timelines and the whole idea of prerendering. Check out my example VEG file, or try it yourself - you will see!
johnmeyer wrote on 9/4/2005, 9:39 AM
I don't think this is anything new in Vegas 6. Vegas has never done a competent job of remembering which segments have been pre-rendered to a hard disk file, and then using that file instead of pre-rendering. I don't think uncompressed has anything to do with it (although it might, because Vegas may not track the exact format used for the pre-render, and therefore if it is anything other than a standard DV format, it will ignore the pre-render).

I wish this would get fixed, not just for the reason you've stated, but also when playing back from the timeline. It has always been my experience that as soon as you change something anywhere on the timeline, all your pre-rendered segments no longer get used, even if that section hasn't been changed. I guess the problem is that with multiple tracks, each of which can be time-slipped and altered in almost an infinite number of ways, it is a very difficult (although not impossible) problem for the programmers to figure out when a certain segment has, indeed changed.
musman wrote on 9/4/2005, 11:48 AM
I agree with what's been said about Vegas and prerendering. It's really not worth doing in many cases imho. What bothers me is that even with a prerender, some more complecated projects will not preview at full speed-which makes it nearly impossible to check your work. As a consequence, I've come to the conclusion that you should plan on relying only on what your computer can do on the fly rather than with a prerender.
Again, this is only my opinion, but I think the way Vegas deals with prerending should be the #1 priority of Vegas 7.
winrockpost wrote on 9/4/2005, 11:52 AM
sneeze ,or look to the left ,or is it the right, all prerenders gone.

ayway tried your sample, and yes it appears to be rendering again
Liam_Vegas wrote on 9/4/2005, 12:01 PM
if I were to follow that advice I would be wasting my timelines and the whole idea of prerendering. Check out my example VEG file, or try it yourself - you will see!

I don't see it that way. I never use pre-renders. However I do often create intermediate renders of portions of the time-line. It works perfectly and does not waste a thing.

When you finish a portion of the timeline simply do a "Render to New Track" of the segment you want. Or else render manually the section and then import it back into the project on tracks above.

This work-flow also makes it simple to re-do small segments of the rendered portions again if necessary (just slice out the changed portion from the rendered tracks and re-do the render for the small section)

And... another question... do you really need to render as uncompressed? What is the final destination format? I do sometimes render to the Sony YUV format as an intermediate (especailly if I am going to finally render to MPEG and I have lots of generated or other graphics in the project). Hey... if you have the space... not a problem anyway... but just curios as to what your end format will be?
Spot|DSE wrote on 9/4/2005, 12:08 PM
How is Vegas supposed to stitch together all your prerenders without rendering again? I guess I don't understand. I don't use prerender much anyway, but even so...you've created a timeline consisting of say....25 prerenders. How is Vegas supposed to create a single file without rendering those together to one file? It's not the same render time stitching pieces together.
Keep in mind as well, you've stashed that prerender in one folder (temp folder) so when you do a file/render as, you're effectively copying that information to a new drive location. Try setting your prerender to the same folder as your final render, and see what happens.

Additionally, how is it you're viewing this project? Externally? Internally?
If it's set to preview externally, do you have a BMD card? Otherwise, Vegas has to downconvert to a compressed format whenever you want to preview, and you'll get choppy frames.
I realize this isn't part of the question youv'e asked, but wanted to point that out.