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Curious Apple>Adobe alpha bug
This is a bug that applies to Generators created in FCP X and Motion, exported as ProRes4444 and then imported into either Premiere Pro or After Effects.
Either in FCP X or Motion, create a project that starts from the first frame with a generator such as a Color Solid (it must be one with a fully opaque alpha channel, so for example the Motion Caustics Generator which has transparency doesn’t behave this way). Don’t scale it down or crop it or mask it – it must be full frame.
Cut the generator so that it doesn’t run for the full length of the project, in other words so that there is transparency after that point.
Export as ProRes4444 and import the result into either Premiere or After Effects.
You will find that the section of the clip that is meant to have transparency does not have any and appears black rather than see-through. Interpret Footage reports the clip as having no alpha channel in the sense that the alpha options are greyed out.
Importing into anything other than these two hosts (including of course the Apple applications) seems not to exhibit this problem.
in other words, something written into the ProRes4444 header is overwriting the alpha channel for the duration of the clip in such as way as to confuse Pr/Ae.
Is this an Apple issue or an Adobe issue?
Simon Ubsdell
tokyo productions
hawaiki -
6 Replies
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It could indeed be an FCP X/Motion issue but then again it’s curious that every other application I tried to open the test with handled the alpha correctly (e.g. Fusion, Nuke, FCP X and Motion themselves). Apart from the Adobe applications – and that includes Photoshop as I’ve just discovered.
Simon Ubsdell
tokyo productions
hawaiki -
Hi Simon,
I was unable to reproduce the issue you posted. I appreciate all of the details but can you please provide a little more info?
– What version of FCPX and Premiere Pro do you have?
– Can you tell me the exact generator to use in FCPX? I tried with some but didn’t see the issue.
– Exact export settings from FCPX?
– System infoThanks!
Peter Garaway
Adobe
Premiere Pro -
Hi Peter.
– What version of FCPX and Premiere Pro do you have?
FCP X 10.2.3
Premiere CC 2015.4– Can you tell me the exact generator to use in FCPX? I tried with some but didn’t see the issue.
You can download an example file here:
https://tokyo-uk.com/Motion/ALPHA_BUG_EXPORT_FCPX.zip
This is an export from FCP X using the “Grey Scale” Generator.
Here’s the FCP X project XML:
https://tokyo-uk.com/Motion/Alpha_Bug_XML.zip
– Exact export settings from FCPX?
ProRes4444 Video Only
– System info
Several different systems and not mine only. My testing has been on Early 2009 MacPro and Mid 2014 MacBook Pro in both El Capitan and Sierra. We’ve also seen this on a recent 5K iMac (don’t know the model). Haven’t yet found a system where we can’t replicate the problem.
I’ve run a lot of tests of this both from Motion and FCP X and tested in both Premiere and After Effects and it is reproducible exactly every time.
If you crop or scale or mask the generator the problem does not persist. If the generator has transparency information (i.e. if the alpha channel is not 1.0 for every pixel in the frame) the the problem does not persist. So for example, if you use the Caustics generator in Motion, you won’t see it.
What are your system specs? What exactly have you tried?
Simon Ubsdell
tokyo productions
hawaiki -
Thanks for the info Simon. I was able to reproduce your issue. This does appear to be an Adobe issue. I will pass the info along.
Thankfully there does appear to be quite a few workarounds for this issue. As you mentioned, crop, scale or mask. Also if you create a gap clip via the position tool at the start of the sequence. That also will preserve the alpha channel. I’m not sure why Solid Gray and a few other generators are causing the alpha channel not to come through in Premiere as many other generators do.
Can you tell me your workflow going from FCPX to Premiere? Hopefully some of the workarounds will keep you going for now.
Best,
Peter Garaway
Adobe
Premiere Pro -
Hi Peter
Thanks for looking into this.
I came across this because I was making graphics in Motion for a Premiere project that a colleague was working on and it really threw us because it seemed impossible for the alpha channel to just vanish.
There are as you say any number of ways of getting around it and it’s quite a special case anyway.
I just wanted to flag it up in case it would be useful to Adobe to know about or other users to be aware of.
Thanks again.
Simon Ubsdell
tokyo productions
hawaiki -
Thanks for bringing it to our attention.
Best!
Peter Garaway
Adobe
Premiere Pro
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