[FFmpeg-devel] VP8 decoder optimization status

[Loren Merritt]

On Tue, 29 Jun 2010, David Conrad wrote:
> On Jun 29, 2010, at 12:43 AM, Frank Barchard wrote:
>
>> Any thoughts about multithreaded decode?
>> 'token partitions' only apply to token decoding, not loop filtering.
>> Could it be handled like mpeg slices and/or ffmpeg-mt frame level
>> multithreading?
>
> MPEG slices, no: there's unavoidable serial dependencies for intra prediction as well.
> Frame level multithreading will work fine, though the discardable probability updates might make it a little tricky.
>
> Random thought for such an implementation: since all the MVs and block 
> modes can be read independently of coeff data, it might be worth it to 
> read them a bit ahead to reduce the locking overhead for MC (if it's 
> significant.)

How would that reduce locking overhead?
Do you plan to run motion compensation, not in raster order by the current 
frame, but rather sorted by the order in which the source pixels will 
finish decoding? That seems rather complicated and unlikely to have a 
large effect even if synchronization were a big problem. Not to mention 
cache thrashing.

--Loren Merritt