Qucktime Render

Dan Sherman wrote on 9/24/2011, 12:17 PM
Not often I have to do this but a client insists on having footages rendered out to Mov. so as to retain the alpha channel.
This is greenscreen footage.
When I attempt to render to Qucktime, a window say upate to QT7.
Have tried to do taht several times without success.
Is there another way to render and retain alpha channel?

Comments

robwood wrote on 9/24/2011, 12:50 PM
many codecs in QuickTime have no alpha available... codecs that do include Animation, PNG, and None.

i use PNG but it takes longer to render, so you may prefer using None or Animation if file size isn't a concern.
musicvid10 wrote on 9/24/2011, 2:38 PM
All versions of Vegas require QT 7.1.6 or later.
Vegas versions before 9.0c require 7.6.2 or earlier.

A codec that you can download with very efficient rendering and Alpha for both Windows and Mac, is Avid DNxHD, LE 2.3.4.
DataMeister wrote on 9/24/2011, 3:11 PM
"Avid DNxHD"

I've been sitting here for 10 minutes trying to remember the name of that codec. All I could think of was OpenEXR which is possibly the best file technology, but also the least fool proof.
[r]Evolution wrote on 9/25/2011, 1:06 PM
Uncompressed .AVI w/Alpha -or- Animation .MOV w/ Alpha would be my suggestion.

His Mac will prefer the .MOV but if he has Flip4Mac or Final Cut the .AVI should work as well.

musicvid10 wrote on 9/25/2011, 11:33 PM
Uncompressed RGBA (AVI or MOV) or Animation from a Windows computer will quite likely give the well-documented colorspace error in the trip to Mac, which will require further intervention, plus the file sizes will be HUGE.

DNxHD is visually lossless, can deliver compressed or uncompressed Alpha, and proper REC 709 luminance is faithfully preserved in the round trip to Mac and back.
It compares favorably to ProRes 422 in all areas and has the advantage of being truly cross-platform.

Plus, DNxHD 8 bits at 145Mbps is about 1/8th the size of uncompressed, iirc. 10 bit, 220Mbps is also an option. The free Cineform codec also has MOV rendering capability, but afaik the cross-platform colorspace preservation is as yet untested, or at least unreported here.
Laurence wrote on 9/27/2011, 7:54 AM
I always use either Quicktime PNG or animation for preserving alpha channel: PNG if it has lots of detail, animation if it doesn't. Will DNxHD hold an alpha layer? I didn't think it could.
musicvid10 wrote on 9/27/2011, 9:42 AM
"Will DNxHD hold an alpha layer?"

Yes, there are options to render the alpha layer either compressed or uncompressed.