I need to convert an QT file (animation codec) to an AVI file while preserving the codec. I've been using the AVI setting within Apple Compressor to convert but the alpha channel is lost after compression.
We went through a similar problem a couple months ago. We ended up having to take the file into After Effects, then export it to an uncompressed AVI file with alpha. Nothing else would work. All other encoding and NLE software would act like it was outputting alpha and the file would read as a 32 bit file, but the alpha channel in the AVI would be all white. After Effects worked ok, but the black portion of the alpha channel was too bright. It read at 15%IRE on a waveform, so we had to mess around with that too.
I'm not sure what the incompatibility is but it was a pain for us and what should've been a simple 15 minute conversion took hours.