FORUMS: list search recent posts

ProRes 4444 alpha channel playback conundrum

COW Forums : Adobe After Effects

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
Chris Brooke
ProRes 4444 alpha channel playback conundrum
on Apr 23, 2018 at 3:00:04 pm

(Moderators please feel free to move this post - I'm putting it here because my original workflow is in AE).

I'm doing some tests for an augmented reality project which is going to involve green screen video. Footage is full 4k (shot portrait). I did a multi level key in AE and exported test initially with Apple Animation codec.

I wanted to experiment with file sizes between different codecs that carry an alpha channel (using Media Encoder) including ProRes 4444 and DNxHR.

Both look fine when the resulting files are imported in to an NLE (Premiere for example) but the ProRes 4444 file seems to show enhanced green spill and bobbling when playing back in VLC or QT Player. I don't get this with the Animation codec - it plays fine in both. I should point out that they key is not completely clean yet but shouldn't look like it does on the left!. I've attached a screen grab showing the identical file playing in both QT Player (left) and Premiere CC17 (right).

Can anyone tell me what's happening here?

Thanks in advance.



Return to posts index

Dave LaRonde
Re: ProRes 4444 alpha channel playback conundrum
on Apr 23, 2018 at 6:02:05 pm
Last Edited By Dave LaRonde on Apr 23, 2018 at 8:20:24 pm

Relax -- everything's okay.
You just need to know that a simple media player can't display alpha channels properly.
PP, on the other hand, displays them nicely.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


Return to posts index

Chris Brooke
Re: ProRes 4444 alpha channel playback conundrum
on Apr 24, 2018 at 11:42:40 am

Hello Dave,

Thanks for the response. If that is the case though why does the Animation export display just fine in both VLC and QT Player but the ProRes 4444 version does not. I have attached an image (ProRes is on the left).

Thanks.



Return to posts index


Todd Perchert
Re: ProRes 4444 alpha channel playback conundrum
on Apr 24, 2018 at 3:38:12 pm

What is your final destination? Taking it into an NLE? I would check there, not with a media player. Some may not show alpha channels, some may show premultiplied incorrectly, where you can see all the edge junk. Check in your NLE.
TC


Return to posts index

Chris Brooke
Re: ProRes 4444 alpha channel playback conundrum
on Apr 24, 2018 at 5:19:36 pm

The destination is not quite straight forward as this is a test for an augmented reality project and the video will play via a bespoke smartphone app developed by another company - hence I've been trialling different codecs for final delivery. The media was fine in Premiere I was just curious as to what was causing the difference between the two codecs playing back in a media player.

It seems that Media Encoder is causing the issue in this instance (as I've mentioned in a post below). Exporting ProRes 4444 directly from the source media in AE with premultiplied alpha plays just fine in QT Player.

I can only assume Media Encoder does something with the alpha channel when transcoding. Shifting from premultiplied to straight? Just a guess...


Return to posts index

Dave LaRonde
Re: ProRes 4444 alpha channel playback conundrum
on Apr 24, 2018 at 5:06:18 pm

My Guess -- you made the Animation-codec version with a Straight alpha channel, but the ProRes version with a Premultiplied alpha channel.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


Return to posts index


Chris Brooke
Re: ProRes 4444 alpha channel playback conundrum
on Apr 24, 2018 at 5:12:03 pm

Actually the Animation export from AE was premultiplied. The prores export was done through Media Encoder which doesn't seem to have an option to select straight or premultiplied.

Whatever Media Encoder was doing seems to have been the problem. Exporting prores 4444 with premultiplied alpha (the default option) direct from from AE plays perfectly fine in QT Player.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2018 CreativeCOW.net All Rights Reserved
[TOP]