[FFmpeg-user] Converting VC-1/MP to VC-1/AP ?

[Ronald F. Guilmette]

For what I am sure are good reasons, XBMC is not able to perform hardware-
assisted video decoding of VC-1 Main Profile video streams, at least not
on the AMD Fusion platform.  XBMC _is_ however more than capable of per-
forming hardware-assisted video decoding of VC-1 Advanced Profile video
streams.

I have a number of files that are encoded as VC-1 Main Profile.  I would
like to know if there is a way to use ffmpeg to convert these files to
VC-1 Advanced Profile, _without_ performing full-blown re-encoding
from scratch.  Also, of course, if there is in fact a way to get ffmpeg
to do this specific kind of conversion for me, I'd really appreciate it
if someone would send me some instructions on how exactly to do this.

Thanks in advance for any assistance.


Regards,
rfg


P.S.  I do not pretend to understand any of the issues that make it
possible for XBMC to make use of hardware accelerated decoding of
VC-1 Advanced Profile streams, even as it is, apparently, unable to
do the same thing for VC-1 Main Profile streams.  However a naive
end luser, such as myself, might, I think, reasonably wonder whether
or not a VC-1 Main Profile stream does not also qualify as a VC-1
Advanced Profile stream, albeit one that uses a subset of the features
available in the Advanced Profile, as would seem to be suggested by
the information on the following page:

    http://en.wikipedia.org/wiki/VC-1

Any light that anyone here might shed on this question/issue would be
appreciated.  (Is a VC-1/MP stream just a VC-1/AP stream that only uses
a subset of the full VC-1/AP feature set?  That is my question.)


P.P.S.  On my specific HTPC hardware, XBMC is able to play all VC-1
Advanced Profile streams and many VC-1 Main Profile streams terrifically
well.  However in the case of some VC-1 Main Profile streams, not so much.
That fact is what is prompting the questions I've asked herein.