How exactly does an alpha channel work?

Sappy wrote on 12/26/2016, 11:44 AM

So I asked a question a plenty while back and now I have a question following up to my previous one. In Sony Vegas Pro 13, I've searched up alot of people using the alpha channels, but in 3 different ways.

1. Is chroma-keying, which is exactly what I don't want

2. Is rendering the video as a .mov based PNG video, which means I can't use any audio and .mov isn't exactly the most trustworthy video file type

3. Using .avi. Many tutorials use this file type to use an alpha channel on, but they skip on the render settings of it, and never tell us on how to actually make it. Some videos straight up just starts by them placing a video into the timeline and alpha channeling it. I only caught the video file when they open properties. And all are .avi and nothing else like .mp4 or such. Which lends me to think that .avi is another video type suitable for this.

 

So my question is, how do you render the .avi video? What type of .avi is it? What preset should I make for it? What preset settings should be in it? Thanks!

~Sap

Comments

Red Prince wrote on 12/26/2016, 12:55 PM

So, to be clear, you’re not really asking how the alpha channel works, but how to render while preserving the alpha channel, right?

Personally, if I need to preserve the alpha channel so I can use it in another editor, I render the video as a sequence of PNG files, as that not only keeps the alpha channel intact, it uses non-lossy compression, which is very important in any kind of digital intermediate.

Alternately, I might render to EXR, assuming the other editor supports it.

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heg wrote on 12/26/2016, 5:31 PM

So my question is, how do you render the .avi video? What type of .avi is it? What preset should I make for it? What preset settings should be in it? Thanks!

~Sap

When you are going to render "video for windows (*.avi)" :

1. go into customize template:
2. Change video format to uncompressed
3. Check "Render alpha channel (uncompressed video formats only)"

Uncompressed avi files are quite big

Sappy wrote on 12/26/2016, 5:46 PM

Thank both of you guys. Really saved me!