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Outline Around Alpha Channel on .flv

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Terry Kean
Outline Around Alpha Channel on .flv
on Mar 27, 2008 at 5:57:27 pm

I'm using FCP to key green screen footage (the key is very clean) and export that using the animation codec. I convert that footage using Sorenson Squeeze with the On2 VP6 codec to carry the alpha channel over to the .flv file. All that works fine. The issue I'm having is that the resulting keyed subject has a darkish outline around it. No matter what setting I try, it's still there. In my editing software, the key is beautiful...no outline. It's got to be happening in the conversion process but neither Sorenson nor On2 will admit there is any issue. Has anyone else had this problem and know how to resolve it?


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MA Carlson
Re: Outline Around Alpha Channel on .flv
on Mar 27, 2008 at 8:00:18 pm

Maybe you are rendering your RGBA clip premultipled instead of straight?



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Terry Kean
Re: Outline Around Alpha Channel on .flv
on Apr 4, 2008 at 4:11:23 pm

Thanks for the response! I re-imported the clip into FCP to make sure and it says the clip has a straight alpha channel...not pre-multiplied.


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MA Carlson
Re: Outline Around Alpha Channel on .flv
on Apr 4, 2008 at 6:16:49 pm

Have you tried the Flash Video Encoder? I get great results with keyed green screen elements (straight alpha always). I would be happy to check out a sample of your clip if you wish.



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Terry Kean
Re: Outline Around Alpha Channel on .flv
on Apr 4, 2008 at 7:46:32 pm

I just might take you up on that in the next few days...That would be awesome! I'd love to see if you get the same results. Let me know what you'd like (QT Animation, Millions +, right?) and I'll make a short clip to send you. Is the Flash Video Encoder a stand alone product or simply a part of Flash itself? Thanks!


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MA Carlson
Re: Outline Around Alpha Channel on .flv
on Apr 4, 2008 at 9:08:50 pm

Flash Video Encoder is a standalone program... I don't remember if it installs automatically with Flash or not, but I don't remember installing it separately -- check the folder where your Adobe programs are installed, there would be a folder named "Adobe Flash CS3 Video Encoder" or "Flash 8 Video Encoder" (might vary depending on version, platform and installation).

Re the test QT clip, yes... high quality Quicktime, Milions+, RGBA, straight would be appropriate.



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Terry Kean
Re: Outline Around Alpha Channel on .flv
on Apr 7, 2008 at 9:21:15 pm

Okay, I've discovered something...When I import my QT animation file back into FCP, I notice the slight outline is there. (It's not there when I initially make the key prior to exporting the clip as a QT animation). I can change the alpha type from "straight" to "black" or "white" in my browser controls. When set to "white" the outline is exaggerated but when set on "black" the outline is gone! Can I get an AMEN?
So now my question is this...how can I change the alpha type settings prior to exporting to QT? I don't know how much you know about FCP (& I don't have Flash)....I tried re-exporting the black alpha clip but I still get the outline after I convert with Squeeze.
I do have a clip I can send you to try...just let me know how!
Thanks!

Terry Kean


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MA Carlson
Re: Outline Around Alpha Channel on .flv
on Apr 8, 2008 at 4:52:32 pm

You can post it somewhere for me to save, or email it to the address in my profile.

I dont have FCP but I can check out the exported clip and see how it is interpreted/converted with Flash Video Encoder and Flash.

If you want, you can also send me a test clip with the green screen intact, and I can compare my keyed/exported clip to yours and see what the difference might be



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Terry Kean
Re: Outline Around Alpha Channel on .flv
on Apr 9, 2008 at 5:40:19 pm

Hey Thanks for all your help. You were right! It was simply a matter of changing the alpha type before exporting from FCP. This whole time I thought it was in the encoding process by Squeeze...What a dolt I am! Anyway thanks again!

Terry Kean


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MA Carlson
Re: Outline Around Alpha Channel on .flv
on Apr 11, 2008 at 1:39:23 am

Cool. Glad you got it worked out.

-G



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