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Compressing Video With an Alpha Channel for PowerPoint

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Jenny CollierCompressing Video With an Alpha Channel for PowerPoint
by on Dec 14, 2010 at 11:10:24 pm

Hi All! This community is an amazing resource and I'm glad to be here.

I need to make some alpha AVI video clips even smaller than they are.
What I’m doing is inserting video clips with an alpha channel into PowerPoint2010. So far, I’ve found only ONE way to do it. If anyone can suggest viable, specific alternatives to any part of this workflow, I would be ecstatic. Here’s what I’m doing:



1) Creating animation in After Effects

2) Rendering full quality AVI clips with alpha channel and no compression --(avg size: 686.6 MB)

3) Re-importing uncompressed clips into new After Effects composition

4) Rendering clips again using Techsmith Screen Capture Codec compression (the only codec on my After Effects list that supports an alpha channel…RIGHT???) --(avg size: 19.9 MB)

5) This is pretty great, but still not nearly small enough. SO,

6) For even smaller files I’ve skipped the last step and rendered instead using TSSCC with Best quality at HALF resolution. (Aesthetics are much less critical than file size here, and half res is plenty good looking for my purposes). --(avg size: about 9.0 MB)

7) Importing clips into PPT2010, where they play with no prob.




This pipeline WORKS, but I’ve GOT to get these files even smaller. I’m talking down around 3 MB or less.

I understand After Effects is a poor program choice for video compression, and that a dedicated compression program is best, but I haven’t been able to find one that would produce viable files. The only Sorenson Squeeze codec that supports an alpha channel produces SWF files, and I need AVI. It doesn’t look as though Microsoft’s encoder is going to work either.

My specific questions are these:

Is there a way to render an alpha channel with the current AE codecs that I’m not aware of? The only way to get an alpha channel to my knowledge is to select RGB+ Alpha in the CHANNELs dropdown (choosing “lossless with alpha” does nothing without that channel setting), and TSSCC is the only codec on my list for which that’s an option. What is this “key frame” stuff I’ve been hearing about, and how does it relate to the creation of an alpha channel?

Would it help, or would I have more options if I rendered my animations from Premier/some other program as opposed to AE??

Is there any dedicated video compression program available (FOR LOVE OR MONEY) that will squish my AVIs and preserve the alpha channel? One with a RANGE of codecs would be best, bc PPT is really choosy.

Thank you so much for the help,
Jenny


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Kevin CampRe: Compressing Video With an Alpha Channel for PowerPoint
by on Dec 15, 2010 at 2:25:15 pm

you might get a better response in the compression forum, but i think you will have problems finding an codec in avi that produces low data rate (small files) and maintain alpha transparency.

part of the problem is that a file that has an alpha is usually intended to be composited on something (other wise why have the alpha, right?), so they tend to also try to maintain a higher degree of quality since this render would be an intermediate step, and thus a higher data rate.

gif and flash are two exceptions, but gif is pretty limited, and you mentioned that swf isn't supported.

i think you may need to look into other ways to decrease file size. you've already dropped resolution, you may also need to drop the frame rate.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW


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Jenny CollierRe: Compressing Video With an Alpha Channel for PowerPoint
by on Dec 15, 2010 at 6:25:03 pm

That's very insightful, thanks for your reply!

I didn't realize frame rate could affect file size, I'll play around with that in AE and see what I get.

Any thoughts on this "keyframing" business? Is that an alternate way to produce an alpha channel?


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Kevin CampRe: Compressing Video With an Alpha Channel for PowerPoint
by on Dec 16, 2010 at 4:31:32 pm

if you were to cut the frame rate in half, it should reduce the file size by half (essentially, it's half as many frames, or half as much data, thus half the size).

[Jenny Collier] "Any thoughts on this "keyframing" business?"

i assume that you are talking about compression keyframes... those are used in a codec that can do temporal (or interframe) compression. often there would be one keyframe per second (the more frequent the keyframes, the high the quality and data rate), and that keyframe is used to help compress the frames around it. any data that does not change much from frame to frame can be compressed further by using compression keyframes.

it's like the codec takes a snapshot at a specific frame, it then compares the next frames (and sometime the frames before it) to that snapshot to see how much has changed. if not much has change (like it was a locked-down camera with somebody just talking) then it can simply say a lot of these pixels are the same as the las, so don't record them. if it was a pan across a carnival, then it would not be able to do a good job of temporal compression and would need to make up ground in intraframe compression (typically macroblock compression like a jpeg).

the short of it, it really doesn't have much to do with alpha channels, though that channel also gets compressed like the other channels, so with compression keyframes, say the alpha never changed from frame to frame, it would get compressed quite a bit.

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW


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Jenny CollierRe: Compressing Video With an Alpha Channel for PowerPoint
by on Dec 16, 2010 at 5:34:09 pm

Kevin,

You were spot on, halving the frame rate SLASHED my file sizes correspondingly...and the clips still look GREAT. You're my hero, no joke.


Interesting info about "key frames"...yeah, I'm used to the term in animation, but I'm sure in the Render Settings menu it means compression key frames as you say. I wonder whether I could save even more file space by fiddling around with them. I'll give it a go.

Thanks again, this has helped me SO much!


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Jason ReinhardtRe: Compressing Video With an Alpha Channel for PowerPoint
by on Feb 2, 2011 at 9:19:29 pm

Hi Jenny, how did you get TSSCC to show up in your after effects render settings? I have the K-Lite mega codec pack (which I believe supports TSSCC) but don't have the option to render using this codec in After Effects CS5.


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Jenny CollierRe: Compressing Video With an Alpha Channel for PowerPoint
by on Feb 2, 2011 at 9:34:44 pm

Boy would I love to know the answer to that question, Jason. At this point, I think it has something to do with the fact that Camtasia (at Techsmith program that uses TSSCC) is installed on the same computer.


If ANYONE can explain why this works, or how to load codecs so they integrate with various programs (for both ENcoding and DEcoding purposes), Please share your wisdom. =(


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Jason ReinhardtRe: Compressing Video With an Alpha Channel for PowerPoint
by on Feb 3, 2011 at 6:14:55 pm

Hey Jenny, another guy in my office has Camtasia installed and sure enough he can export from After Effects to TSSCC! Unfortunately PPT2010 doesn't seem to recognize the alpha channel in the TSSCC file (it does recognize it in an uncompressed AVI) when rendered RGB+A. Not expecting you to have a magic solution, just lettin you know Camtasia seems to be required for exporting to TSSCC :)

Best,
Jason


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judah houserRe: Compressing Video With an Alpha Channel for PowerPoint
by on Feb 3, 2011 at 6:35:43 pm

AND - In AE CS3 the TechSmith codec file reimported with the alpha intact, but not in CS5. Odd indeed. Still can't get PPT 2003-2010 to recognize alpha on either Uncompressed AVI or TechSmith version.


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