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Old March 15th, 2010, 09:27 AM   #1
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Intermediate render with alpha

I am a home video maker that has mostly 1440x1080 60i source material(HDV and AVCHD). I have created some lower thirds and other effects that I would like to render out and use as source throughout the video. Some of the effects have extensive render times, and I would like to just utilize the intermediate, pre-rendered clip. So far, I am unable to find a render format that can maintain the alpha channel for this later compositing. It seems to always go to black. Help?

Thanks, Mike
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Old March 15th, 2010, 09:40 AM   #2
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Choose AVI, open the Custom settings, choose "Uncompressed" and then check to box to "preserve alpha". This works great as long as the clips are very short as uncompressed takes a significant amount of space. If you have longer clips, you just have to make sure you pick a format that supports alpha channels.
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Old March 15th, 2010, 11:55 AM   #3
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Thanks Edward for the reply, and for all the other adivse you have provided over the years.
I do not venture in to "Custom" settings very often. Mike.
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Old March 15th, 2010, 01:29 PM   #4
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A good free format that lets you do an alpha layer is Quicktime .mov with PNG compression. It uses PNG compression which is lossless but compresses the heck out of simple things like lower thirds animations.

You do have to go into the media properties however on playback and enable the alpha layer playback.

One negative thing I've found about video with an alpha layer is that there always seems to be a bit of a black halo around the subject. This is the case with uncompressed or any other codec but I don't know why.
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Old March 15th, 2010, 02:46 PM   #5
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To avoid a black halo around the subject when using a codec that supports an alpha channel (32 bits), just be sure to choose the "Straight alpha" option and not "premultiplied".
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Old March 15th, 2010, 06:11 PM   #6
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Also supporting alpha channel:
quicktime with the "Animation" codec.
Lagarith.
DNxHD (I haven't tried this one).
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Old March 16th, 2010, 08:17 AM   #7
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Personally, I avoid the "quicktime" options as quicktime clips are NOT very "quick" to use in Vegas. In fact, I don't even have quicktime installed. As long as the clips are short, uncompressed is fine. If the lower third is static, a single PNG will work!
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Old March 16th, 2010, 09:53 AM   #8
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The rookie reporting back with great success using uncompressed AVI file. The effect clips are only about 5 seconds in length, and I have alot of disk space, so size is not a concern.

It was actually multiple tracks of HD .mov (QuickTime?) files combined with multiple AVCHD files and effects that causing the lengthy Q6600 render times that I wished to reduce.

I am running Pro 8.0c, and experienced some Vegas crashes trying to render the everything at once. After splitting up the scene, and performing intermediate renders, all is good. Vegas smart render really helps this scenario by not re-rendering the intermediate .m2t clips.

I can say this using HD source, the Blu Ray video created by Vegas looks magnificient on a HD set.

Thanks again to all,
Mike
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Old March 16th, 2010, 06:59 PM   #9
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Michael, - that's great news. What is your editing computer ?

I am also a home video maker and have had no joy with Veg 8 or 9 rendering out AVCHD to AVI with no effects, just cuts & dissolves. It all plays well off the timeline which has a mix of DV (AVI), and a small amount of AVCHD, but crashes when I try to render out. - I thought Veg 9 might have fixed it but no. I use a core 2 Duo/2.9g 6g Ram. and thought it would simply take a while to render but not so, just crashes.

Tanks, (St. P. Day)

RonC.
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Old March 17th, 2010, 03:36 AM   #10
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Quote:
Originally Posted by Seth Bloombaum View Post
Also supporting alpha channel:
quicktime with the "Animation" codec.
Lagarith.
DNxHD (I haven't tried this one).
Seth, is it possible to retain the ALPHA channel using Lagarith when rendering in Vegas? I've tried this and I get a stubborn background? Uncompressed, sure, but Lagarith? And I do have RGBA selected in the Lagarith configure. I'd really like to know how to do this with Lagarith?

I do get an Alpha out from Particle Illusion when using Lagarith and select Premultiplied back in Vegas and get my Particles over my videos.

Grazie
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Old March 17th, 2010, 12:17 PM   #11
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I thought I'd done alpha with Lagarith in Vegas. I'm going to have to go back and see if I can. Oops, no joy here - sorry about that Grazie.

Recently, I've been using QT-Animation. What Edward says above is absolutely true, anything QT is slow for preview performance in Vegas, but, it does work. Much of my recent work is cross-platform over to Mac, and QT-Anim has been pretty bulletproof both directions.
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Old March 17th, 2010, 02:47 PM   #12
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Quote:
Originally Posted by Ron Cooper View Post
Michael, - that's great news. What is your editing computer ?

I am also a home video maker and have had no joy with Veg 8 or 9 rendering out AVCHD to AVI with no effects, just cuts & dissolves. It all plays well off the timeline which has a mix of DV (AVI), and a small amount of AVCHD, but crashes when I try to render out. - I thought Veg 9 might have fixed it but no. I use a core 2 Duo/2.9g 6g Ram. and thought it would simply take a while to render but not so, just crashes.

Tanks, (St. P. Day)

RonC.

Ron,

I have Vista 64 system, q6600 (no overclock), 8GB, three WD drives of varying sizes. I was unsure if my render crashes were related to the HD .mov files, the AVCHD files, effects, or combo of all. I know the .mov files with effects take a loooongg time to render.

I typically generate 1440x1080 60i m2t files as my target format. If I am burning DVD for non Blu Ray players, I simply let DVDA or Nero down-res my final m2t. I may go after Sony for some PS3 sales commissions after this weekend basketball team party. Our host had both DVD player and PS3, so I brought along both formats. Lots of folk with older model camcorders were seen driving to BestBuy for new ones after a side by side viewing :-)

Because my stuff is all non-commercial(vacations, sport teams, concerts, etc..) , if I have to re-render some HD material to an intermediate m2t file I find it still looks great to my untrained eye. Smart rendering seemingly helps the intermediate renders maintain their final quality. I have no proof, just intuition, that the mixing of .mov, .mts, and m2t file formats on the timelime may also play a role. Sorry I can't be more precise, but I tend to just "get it to work" and then move on without much in depth investigation.

FWIW, the 64 bit Vegas Pro 8.1 did not help my cause, but it sure did utilize the extra system RAM.

Mike
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Old March 17th, 2010, 03:49 PM   #13
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What am I doing wrong? I rendered a chroma keyed clip to QT Animation 32bit and put the QT back into Vegas. In Vegas, I chose "Straight (unmatted)" for the alpha type for that QT clip.

But when I put the rendered QT clip on a new track above the original and mute the original, I get a dark halo around objects in the scene - easy to see when the third (lowest) track is a solid light blue color.

When I mute that QT track and unmute the original (middle track) chroma key clip, I can see a clean key with absolutely no dark halo. Claire Watson - can you help?
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