Exporting video with alpha channels from Premiere Pro and Adobe Media Encoder
QE Manager, Aurobinda Datta gives this handy method of testing alpha channel support for Adobe Media Encoder:
If you select to export at 32 bit color depth, QT and WMV (with the codecs selected below) AME will write out an alpha channel by default (There is no user input needed here).
How to verify that it works:
1. In Premiere Pro create a DV sequence
2. Create a New Item> Bars and Tones with settings same as the DV sequence and then drag it to sequence.
3. Select clip and then from effect controls, scale it down (You would get black border all around which is Alpha)
4. Export to AVI (say alpha.avi) with bit depth 32 bit (codec = none)
5. Create a new dv sequence (say test) and then create a new item> Universal Counting Leader (UCL), and drag it to this sequence to video track1.
6. Import the alpha.avi file in Premiere and then drag it to sequence test and drag it to video track 2
7. Now you should see the UCL in the background and in the foreground you should see the bars and tones.
8. If you repeat step 4 with bit depth of 24 bit (no alpha), in step 7, you will not be able to see the UCL in the background (you would get black border)
32 bit color depth means 8 bits per channel multiplied by four channels.
Also a new Help topic, Exporting video files with alpha channels, is in the works, and will go live with the next update of English Help.