H.264/mp4 videos enormous CPU usage

Question

I can watch my TV-quality h.264/mp4 640x480px / 25fps videos
in fullscreen
(encoded in MPEG Streamclip, multipass, b-frames,
deinterlaced)
on my seven years old G4 Digital Audio, 466 Mhz without any
dropped frames.
As long as I use QuickTime, I can do that.
On the other hand the same video plays less smooth on my G5
Dual 2.7 Ghz
if I watch it in the flashplayer (newest update...).
I just wonder, if Adobe realizes that they really should work
on
the high CPU usage of their flashplayer while playing back
h.264 videos.
Or is this the price for the smal flashplayer size and can't
be changed?
After doing several tests, I am afraid TV-quality h.264/mp4
vidoes do stutter for about 50%
of the current online viewers.
Does anybody know, if the developers at Adobe are working on
that?
Thank you for any replay

Answer 1

I think part of the problem here is that flash allows to
compose additional graphical elements onto the video. So it has to
do colorspace transformations and scaling in software.
Recently I ran OProfile while watching a flash video (not
H.264) and found that it spends a significant amount of time in a
routine that does BGR32 to RGBA32 conversion. For fun I tried to
write a faster version and ended up with a MMX version that is 40%
faster and a MMXext version that is 67% faster. For reference,
plain memcpy is 44% faster. (all values for memory blocks >>
L2 cache, MMXext can be faster than memcpy because of
prefetchnta/movntq).
Nobody at Adobe reads this forum.