Alpha channel in H.264 bit-stream

[kiani]

Hello,

I want to include an alpha/auxiliary channel in H.264 elementary stream. I am using H.264 reference software JM18.3 provided by JVT. To my knowledge, the H.264 standard discussed syntactic facilities to include auxiliary coded pictures in the bit-stream; but its optional for encoders/decoders to implement these facilities.

Is there any h264 codec known to humanity which can do the job?

There is a similar post in the following address, but I insist to use H.264 standard (not MPEG-4 part 2).

http://doom10.org/index.php?topic=1149.0

thanks in advance

[kiani]

Sorry, Second question:
How to encode alpha information as a separate elementary stream with single plane gray-scale pictures ? I mean that the resulting bit-rate of the gray-scale bit-stream must be two-third of a similar colored video bit-stream.

thanks

[jmartinr]

Make that two-thirds. YV12 means only 4 bits out of 12 are for color information.

[kieranrk]

Quicktime has an alpha channel which it stores in an unregistered SEI. It is not documented.