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Steve Griffiths
Inspiring
January 18, 2022
Answered

Create luma matte export directly from Premiere Pro

  • January 18, 2022
  • 1 reply
  • 1891 views

I have a project that requires the program to be output as seperate (Luma) matte/key file and ‘fill' file for live keying on a show.

(The playback system requires this particular format - files with an alpha channel - like Prores 4444 won’t work).
It’s a simple animated frame with animated ‘glows’ and text that will be broadcast ‘filled’ with live vision.
 
Is there an easy way to output a Premiere Pro sequence and create a luma matte export?
(the sequence has a bunch of alpha clips in it)
 
I can do it by exporting Proress 4444 and then re-render that from After Effects to create a ‘matte' export
but wondered if anyone has an easy way to do this directly out of Premiere Pro.
Correct answer chrisw44157881

Premiere has an effect called Track matte that works in 32bpc. Do a quick test with a few frames and see if it fits your needs. You might have to setup another layer on top for it to reference.

1 reply

chrisw44157881
chrisw44157881Correct answer
Inspiring
January 19, 2022

Premiere has an effect called Track matte that works in 32bpc. Do a quick test with a few frames and see if it fits your needs. You might have to setup another layer on top for it to reference.

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Steve GriffithsAuthor
Inspiring
January 19, 2022

That worked perfectly - white layer with track matte key to a nest of the original fill sequence. Thanks Chris!

S
Steve GriffithsAuthor
Inspiring
January 21, 2022

So, Chris and Steve ... how about unpacking this a bit? Sounds like a nifty workflow trick, but it would be nice to have a step-by-step here.

 

Neil


Based on Chris's suggestions - this is the workflow we used:

 

In this use case we had a .tga sequence (with alpha) of an animated rectangular frame. Plus a bunch of animated Essential Graphics (text) created in Premiere Pro overlayed with an animated flare/glint ( via Prores 4444).

 
This main sequence in Premiere Pro became our ‘fill’ clip.
 
This sequence was then dropped into a new sequence onto video track 2 with a full frame white solid on video track 1.
This becomes the ‘Luma Matte/key’ sequence.
Track Matte Key was applied to the white solid and set in ‘Effects Controls’ to ‘Matte' using ‘Video 2’ and 'Composite Using’ ‘Matte Alpha’.
 
The result in this sequence is a white image wherever a ’solid’ part of main sequence appears or a shade of white for any soft edges and transparent parts of the fill.
Black or shaded areas represent what will be the ‘live’ component of the show.
 
Both sequences are exported (in this case Prores 422 but usually DNx120). Make sure to name the clips to include which is the ‘fill’ and which is the ‘matte’.
 
If you want to check that it works - bring the exported files back into Premiere Pro and in a new sequence put the ‘Matte’ clip on V3, the 'Fill' clip on V2 and what you want to represent the ‘live’
component of the effect on V1. Apply the 'Track Matte Key’ effect to the V2 clip (your fill clip) and set the controls in the Track Matte Key to ‘Matte’ to 'Video 3’ and ‘Composite’ to ‘Matte Luma’.
 
At the outside broadcast the two files will be played in sync and the ‘matte’ clip will be fed to the vision switchers luma key channel or downstream keyer.
And the ‘fill’ clip will fill the matte key.
 
You’d think in this day and age we’d be able to provide video files with alpha channels directly to achieve the same result but no, major broadcast playback systems (like EVS) need it this way, I think (guessing) because vision switchers have never been built with alpha channels in mind.
*Chyrons can take .tga sequences (with alpha) and Animation codec with alpha clips but this is impractical for anything much longer than 15 seconds.

 

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