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TheFosterHouse
TheFosterHouseCommunity Member
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CS5: ProRes 4444 Alpha issue rears it head again in a strange way

May 10, 2011 10:12 AM

So here's a strange one: I've found that if the first frame of a composition is completely opaque (such as using a solid to fade from black) then any QT Movie rendered with ProRes 4444 + Alpha will not include an alpha channel. I've replicated it on multiple machines and triple checked my MediaCoreQTCodecRulesCS5.xml to ensure that it's correct. Here's the steps to recreate this:

  1. create a new comp (Project bit depth = 16bpc)
  2. create a new solid with the same dimensions as the comp
  3. at Frame 0 create a keyframe for the Solid's opacity (Keep it at 100%)
  4. move down 5 frames in the comp and create a new keyframe by setting the Solid's opacity to 0%
  5. set the work area to 1 second
  6. Render a movie using ProRes 4444 RBG+Alpha

 

The resulting movie will have no Alpha channel. If you watch the movie being rendered with Caps Lock off and 'Toggle Transparency Grid' active, then you can see the alpha channel while the render is going. If you render using Animation Compression RGB+Alpha, it will be correct. You can also replace the solid with footage as long as the first frame of the rendered comp is completely opaque and the issue is still there. Move the solid or footage down in the time line 1 frame so the first frame of the comp has a transparent alpha channel, then the movie rendered from that will be correct. This has only been tested and confirmed on the Mac and only CS5. If anyone can test and confirm the PC CS5 and Mac & PC CS5.5 it would be greatly appreciated.

  • Rick Gerard
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    Rick Gerard,
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    May 10, 2011 9:48 PM
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    Make you settings look like this:

    ProRez444.png

    All should work just fine. You'll get a warning if your project is 8bit color, but it will still work.

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  • TheFosterHouse
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    TheFosterHouse,
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    May 11, 2011 10:46 AM
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    That doesn't work. The Alpha channel is still not rendered into the QT Movie.

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  • Rick Gerard
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    Rick Gerard,
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    May 11, 2011 5:51 PM
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    It works just fine for me. Do you have any odd video codecs installed?

     

    Here's a few frames rendered with those settings. I'd suggest you download it and give it a test. Played with the QT player you won't see the transparency, but drop it into PPro or FCP or AE and it's there.

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  • TheFosterHouse
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    TheFosterHouse,
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    May 11, 2011 6:18 PM
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    Create a new solid at the first frame of that comp and make the solid only one frame long, then render it again. The problem is that if the first frame has no alpha, then nothing passed it will have an alpha either.

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  • Rick Gerard
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    Rick Gerard,
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    May 11, 2011 10:26 PM
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    You've found a bug. I'm not sure where the problem is. If I render out an image sequence or an Animation Codec file, then drop it in Media Encoder or Compressor to render a ProRez 444 with alpha channel I occasionally get the bug. You can't tell anything from the Quicktime Player but you can see the error in AE.

     

    I discovered that if you put one even partially transparent pixel anywhere in the frame the alpha renders perfectly, but as you pointed out, when the first frame or few frames have a 0 alpha value the renders are funky. I just don't know if it's AE's problem, Adobe's problem, or an Apple problem because I can break it in compressor or Media Encoder or I can make it work in either.

     

    I'd file a bug.

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  • TheFosterHouse
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    TheFosterHouse,
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    May 18, 2011 12:13 PM
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    Thanks Rick for testing and confirming. I didn't think to check Media Encoder or Compressor, that makes this issue a little more puzzling. Bug report has been filed and I've received confirmation that they're looking into it.

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