[x264-devel] ”ultrafast“ preset preformance decrases after commit "Unify 8-bit and 10-bit CLI and libraries"

[Timothy Pearson]

On 02/01/2019 10:07 PM, wangguan (D) wrote:
> 
> 
> Hi, all
> 
>  
> 
> After the commit “Unify 8-bit and 10-bit CLI and
> libraries"(http://git.videolan.org/gitweb.cgi?p=x264.git;a=commit;h=71ed44c7312438fac7c5c5301e45522e57127db4),
> the “ultrafast” preset costs more time encoding.
> 
> The commit “Unify 8-bit and 10-bit CLI and libraries" moves the function
> param_apply_preset from common/common.c to common/base.c , and also
> change the content of param_apply_preset.
> 
> Before the commit, in common/common.c, the old version
> param_apply_preset sets “param->analyse.i_trellis = 0;” if preset is
> ultrafast
> 
> After the commit, in common/base.c, the new version param_apply_preset
>  misses to set “param->analyse.i_trellis = 0;” if preset is ultrafast.
> 
>  
> 
> I think it’s a bug, i_trellis’s default value is 2, and i_trellis is set
> to 0 in “superfast” and “veryfast”.  So it makes no sense for i_trellis
> to be 2 in “ultrafast”.
> 
> Fixing this can restore the performance in “ultrafast” preset.

I noticed the same thing.  Took a bit of time to track down since the
settings for each of the presets aren't exactly easy to find.

-- 
Timothy Pearson
Raptor Engineering
+1 (415) 727-8645 (direct line)
+1 (512) 690-0200 (switchboard)
https://www.raptorengineering.com