After further research, it appears this is possible with the use of custom shaders. Unfortunately, I cannot find a shader to do the job.
I've found a thread which states its been solved, but when I import the shader it throws up GLES 2.0 incompatibility errors and says the shader needs both fragment and vertex programs to be compatible with OpenGLES2.0.
Heres a link to that thread on the Unity forums:
Does anyone know how to fix this issue or to add vertex program information into a shader to upgrade it for Unity's newer versions?
I have a video with embedded alpha. I understand that Theora removes the alpha information on import, but I've seen others say you can accomplish this with 2 movies on planes, one with RGB and one with A, then use the RGB movie as primary texture and Alpha movie as _Mask texture.
While having two files to pull it off is not ideal, it will work for what I need now. Either a quick 2-texture alpha-blend approach or a way to use a single video with alpha channel is what I need.
Thanks to anyone who can help with this!