[FFmpeg-devel] [PATCH] FFV1 rectangular slice multithreading

Jason Garrett-Glaser darkshikari
Thu Oct 14 15:33:08 CEST 2010

On Thu, Oct 14, 2010 at 5:59 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> Hi
> Following patchset makes ffv1.2 much faster on multiprocessor systems
> (requires version to be set to 2, which needs you to edit the source if you
> ?want to try as 1.2 bitstream is not finalized yet)
> Compression wise 4 slices with foreman and large gops (300 frames) perform
> slightly better (0.05% IIRC) than 1 slice.
> With small gops (50 frames) compression is worse with the rangecoder and the
> large context model by 0.8% otherwise better too.
> (its quite obvious why its worse in that case and ill be working on that ...)
> Comments welcome, bikesheds not, and ill apply this soon

>+    if(f->num_h_slices > 256U || f->num_v_slices > 256U){

The max slices is 256, but this allows for up to 65,536, which doesn't
seem right.

How will this handle frames that aren't evenly divisible by the number
necessary to slice the frame?  It doesn't seem to handle slices that
aren't identical in size; will there be padding or what?

Dark Shikari

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