[x265] patch for faster intra

[Steve Borho]

On 08/01, dave wrote:
> I am submitting a patch to implement the faster intra search suggested by
> Steve Borho here:
> 
> https://mailman.videolan.org/pipermail/x265-devel/2014-July/004873.html

nice!

> The patch is implements the faster search in slicetype.cpp.  The same
> approach can also be used in analysis.cpp but it's a little more than a
> simple cut and paste though it shouldn't take long.

yep

> TEncSearch.cpp also calls intra_pred_allangs for which this is the faster
> alternative but at first look, TEncSearch.cpp is more complex.  Depending on
> what is desired, either this search could greatly simplify this part of
> TEncSearch.cpp or it might not be applicable to what TEncSearch.cpp is
> doing.  I will be looking into it.

it should also apply here; this function is a little more complicated
because it keeps a "best N" list of modes, and then performs
rate-distortion measurements (encodes each option and records the actual
distortion and bit cost) to select the final intra mode.  The same 'fast
scan' mode could be used to build the 'best N' list. But I imagine most
presets that use this RDO version of intra will not want a fast scan.

-- 
Steve Borho