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No 32 bpc option for Alpha Output

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amir baigmoradi
No 32 bpc option for Alpha Output
on Apr 4, 2018 at 3:44:24 am

Hello Fellow Pros,

I have a dilemma and have been scouring the archives for hours -- no luck and hoping someone can school me.

I have 1920x1080 Pro Res 4444 clips (originally h.264 DSLR footage) that I need to persevere the Alpha Channels and the chroma keying I did for delivery to my client .

I've read every where that I need to export either Pro res 4444, animation, jpeg2000, etc codecs at 32 bpc + alpha. I get this --

BUT the problem is that Adobe Media Encoder CC on my machine doesn't give me the option to export anything at 32bpc + Alpha on any of the alpha preserving codecs. Only 8 and 16 bpc + alpha.

I'm stumped.....

Files are for use in Q Labs and none of the exports at 16 bpc +alpha I've exported work in Q Labs all the while working fine in Premiere when I re-import.

Any input or wisdom would be greatly appreciated.

I have a 2012 Mac Pro running High sierra 10.13.1 8gb ram 2.6GHz core i7 -- maybe my machine is just incapable?

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Jeff Pulera
Re: No 32 bpc option for Alpha Output
on Apr 4, 2018 at 2:33:31 pm

I run PC, so do not have ProRes output capability, but here's how I see it.

If you export 8-bit video, there are 3 color channels, being red, green and blue. EACH of those 3 channels is 8-bit, which in effect provides a 24-bit image. If you add an alpha channel, that is another 8-bit channel, so 24-bit plus 8-bit = 32-bit. So I think whatever you may have read is just worded confusingly. A 32-bit image already includes the alpha channel.

Export a short sample with what you think are the correct settings, bring that clip back into Premiere timeline and see if there is alpha transparency - put the alpha clip on V2 with something behind it on V1 to see if V1 clip "shows through".

If you can perhaps post a screen shot of the Output Settings panel that actually shows the ProRes output options available, I or someone else here should be able to discern what is correct and offer some guidance, but I need something to look at to understand the Mac options that I don't have available on my PC here.


Jeff Pulera
Safe Harbor Computers

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