I tried locally on my computer and it did not work.
Looking with PIX, I could see that the texture located in the GPU that comes from the video has no alpha channel. However, I don’t know if it’s because there’s really no alpha channel in the video itself or because webgl would not handle the alpha channel of a video…
[…] Ok, the video has no alpha channel. Using this video it does work with this PG:
http://localhost:1338/Playground/index-local.html#LT4WHM#1
Of course you should replace the temp/Bear.webm path by another one.