I found some curious behavior when finally outputting to tape on this project. I pulled the alpha channels out and they were screaming hot as discribed but then when doing a digital cut the levels were 0 to 700 millivolts. Stopping the output and bang the levels are screaming again. If I put a submaster over the alpha channel and render that then the levels stay hot when doing a digital cut. In the past I've seen odd behavior with alpha channels pulled out from matte keys where it would be an urecognized or incompatible resolution. The stuff I'm seeing today seems to indicate that Avid is somehow keeping tabs that the matte key alpha is full swing 0to 255 and seems to clamp it down or clip it to legal levels on digital cut unless it's rendered in with a submaster effect on top. Very weird.
--- In Avid-L2@yahoogroups.com, John Moore <bigfish@...> wrote:
>
> I'm building a roll in reel for ingest into an EVS unit for a live show. I've got matte key elements and I've separated out the fill and alpha video. As I understand Avid's matte key structure the fill should be 16-235 and the matte key alpha is actually full range 0-255. Now when I pull out the alpha channel I have super whites and blacks as would be expected. I am hesitant to color correct this into 16-235 as I don't want to distort how the switcher will interpret the key signal. I'm building fill on one tape and alpha on another tape with matching time code so they can sync roll when ingesting into the EVS unit at the remote. I know the TD can tweak his linear keyer but I'm curious if anyone more familiar with the EVS feeding a key signal to a switcher if I should infact bring the matte signal to reside within 0 to 700 milllivolts? TIA
>
>
> John Moore
> Barking Trout Productions
> Studio City, CA
> bigfish@...
>
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