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FCP and alpha chanel?
i have some long interview clips shot against a green screen… since the clips are 1080i the render time for the keying is fairly long even on my quad core G5, 4GB RAM… is it possible to render it out with an alpha channel in place bring back into FCP and add in the motion backgrounds… graphic elements… etc???
or perhaps some work flow suggestions… i understand if there is limited choices…
BTW using the ultimatte and mattenee system, which i must say, is fabulous at everything over DV25… clean keys!
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3 Replies
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The only codec that supports an alpha channel is Animation, which would need a render to play in the timeline anyway. So you really wouldnt be saving any time.
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I recently had a similar problem. I had bad greens screens that my compositor fixed in Shake on a unix box. he gave me targa sequences that I needed to convert to single movie files with the alpha data intact.
Although it looks as if FCP will export to codecs with “million+” colors (alpha channel) it doesn’t work. I tried exporting uncompressed animation files from FCP using “quicktime conversion” and when they were re-imported ther alpha was not there.
I used Quicktime Pro to open the image sequence and then exported the media in an uncompressed animation codec and everthing worked fine. Imported back to FCP to key them over background plates and they worked perfectly. And for some reason they rendered faster than native media files as well.
FYI avoid round tripping anything to Motion. Again I’ve found that if I export an animation file from Motion and import it to FCP it renders in a fraction of the time. i.e. a 5 second lower third rendered in 1;30 as a Motion file and as a animation file it took 5 seconds!
cheers,
greg -
If you want to export with an Alpha Channel in the Animation Codec using Quicktime Conversion, you must make sure your clip is NOT rendered. If its rendered, the render file will be referenced, which is a composite..so you wont get the alpha channel.
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