[FFmpeg-devel] Question about parallelizing h264 decoding

[Reimar Döffinger]

Hello,
On Thu, May 10, 2007 at 05:01:00PM +0200, Thorsten Jordan wrote:
> since it seems that the performance of a single core is not enough for
> full HDTV decoding, one obvious alternative is multithreading on SMP
> systems.
> I know that the current h264 decoder can't decode multithreaded, but i
> want to discuss some ideas how this could be done.
> 
> Two choices come to my mind:
> 
> 1) decode slices in parallel - problematic, because intra-frame
> references and many data dependencies, also because of difficult
> parallelization of cabac decoding etc.
> 
> 2) decode frames or even GOPs in parallel - this one i want to discuss a
> bit further.

Hmm. It might be an obviously bad idea for those who actually have
experience, but how about an idct (or other dsputil stuff) implementation
that just submits the task to different threads + a barrier operation
that waits for the all the threads to complete at the end?
Of course it is not optimal (lots of overhead and probably bad cache
use) but it doesn't sound quite as invasive and easy to extend to e.g.
Cell...

Greetings,
Reimar D?ffinger