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After Effects Alpha Channel Question
Hi,
Have had some motion titles supplied as and animation codec (rgb + apha) which i had to import into my Avid Symphony for onlining. Upon import, the titles behaved incorrectly when fading up (instead of cleanly fading up, they went from grey to white). For this job, being a 3 min piece, the workaround was to take the video into AE and render it all there, but obviously i’m not keen on this approach as it hinders my ability to tweak the final output from the Symphony.
Now obviously, this is a problem with the Alpha channel settings somewhere in the workflow, and hopefully something obvious. My current suspicion is that it is a straight vs premultiplied issue, but i’m not sure and if this occurs again in future i need to be able to instruct whomever creates the titles what to supply me,
Can anyone shed some light on this problem?
Cheers
Dan
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5 Replies
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AFAIK, Avid only supports straight alpha.
(Premultiplied looks ugly)
So, check your files what they are. If they are premultiplied, you can use AE to render them to straight.In older versions there was a ‘blooming’ bug, incorrect fading.
You can try adding a dissolve instead of fading up opacity with keyframes, or vice versa.The most brute way if nothing works is to make a copy of your video on a higher track, and fade out to the composit below (video + anim)
That should always work…hth,
Bouke
https://www.videotoolshed.com/
smart tools for video pros -
Thanks for the reply. Will give these a try later and hopefully all will be well.
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No good so far i’m afraid. Re-rendered as straight and the qt imports as completely transparent.
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Make sure you set ‘interpret footage’ right
(interlaced or not does not really matter if you do not scale, but interpreting the alpha right is essential, tell AE what it is, what it will become is set in the output / render settings)If the alpha does not come across, you probably have used an Avid codec.
(I take it you know to set the exporter to millions +, and not have a solid background in your comp…)Some avid codecs do not support alpha, although they appear to do so.
Try Animation at 75% quality (100% results in a 4:4:4 file, that’s overkill).hth,
Bouke
https://www.videotoolshed.com/
smart tools for video pros -
Hi. Thanks again for your reply. Just managed to get it. Rendered out as straight and then tweaked my import settings according to this post i found over at the avid forum (not been on there since my trainee days!)
https://community.avid.com/forums/p/93106/530003.aspx
Come very counter-intuitive settings there re: colour space & not inverting alpha.
So thanks, your advice was perfect – just had to then re-tweak the Avid import settings in a way that runs contrary to all past experience.
Cheers
Dan
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