Expression to Split & Delete Black Footage from Pre-Rendered Video
by Roger Alexander on Sep 23, 2012 at 12:47:54 am
I mainly edit in sony vegas pro 10 and bring in some clips to after fx.
Im shooting a music video with multiple scenes and I have all of my green screen footage on one track in vegas. I rendered all of those scattered clips down to one file (with empty black footage inbetween each green screen clip) to bring into After FX to use keylight. So I have black space in the parts where a green screen clip does not play. I would like an expression in after effects to evaluate my rendered file for footage that is empty and black. When it gets to a part of the footage that is just a black empty screen, I want it to split that section and delete it from my composition. AFTER DELETING I DO NOT WANT TO CONDENSE DOWN THE EMPTY SPACE/SPACE THAT WAS BEEN MADE BY DELETION. I would like for all of my green screen footage to stay in the same position at the same time code. Before I run the expression, if my rendered file is 5 minutes long, after running the expression I still want it to be 5 minutes long except with the black parts split and deleted from that layer. That way, I can easily sync this back up when I return my rendered footage from After FX back into vegas.
Let me know if this makes sense guys, thanks a ton!
Re: Expression to Split & Delete Black Footage from Pre-Rendered Video
by Dan Fredley on Sep 23, 2012 at 4:26:07 am
It would be a lot easier to export an alpha channel out of your editing program instead of black than to write a script for that. An expression can turn down the opacity of the layer by using sampleImage(), but it renders pretty slow.
This script might help to a certain degree: