[FFmpeg-devel] [RFC] DXVA2 decoding and FFmpeg

[Stefano Sabatini]

On date Tuesday 2015-06-16 10:20:31 +0200, wm4 encoded:
> On Mon, 15 Jun 2015 17:55:35 +0200
> Stefano Sabatini <stefasab at gmail.com> wrote:
> 
> > On date Monday 2015-06-15 11:56:13 +0200, Stefano Sabatini encoded:
> > [...]
> > > From 3a75ef1e86360cd6f30b8e550307404d0d1c1dba Mon Sep 17 00:00:00 2001
> > > From: Stefano Sabatini <stefasab at gmail.com>
> > > Date: Mon, 15 Jun 2015 11:02:50 +0200
> > > Subject: [PATCH] lavu/mem: add av_memcpynt() function with x86 optimizations
> > > 
> > > Assembly based on code from vlc dxva2.c, commit 62107e56 by Laurent Aimar
> > > <fenrir at videolan.org>.
> > > 
> > > TODO: bump minor, update APIchanges
> > > ---
> > >  libavutil/mem.c          |  9 +++++
> > >  libavutil/mem.h          | 14 ++++++++
> > >  libavutil/mem_internal.h | 26 +++++++++++++++
> > >  libavutil/x86/Makefile   |  1 +
> > >  libavutil/x86/mem.c      | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
> > >  5 files changed, 135 insertions(+)
> > >  create mode 100644 libavutil/mem_internal.h
> > >  create mode 100644 libavutil/x86/mem.c
> > > 
> > > diff --git a/libavutil/mem.c b/libavutil/mem.c
> > > index da291fb..0e1eb01 100644
> > > --- a/libavutil/mem.c
> > > +++ b/libavutil/mem.c
> > > @@ -42,6 +42,7 @@
> > >  #include "dynarray.h"
> > >  #include "intreadwrite.h"
> > >  #include "mem.h"
> > > +#include "mem_internal.h"
> > >  
> > >  #ifdef MALLOC_PREFIX
> > >  
> > > @@ -515,3 +516,11 @@ void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
> > >      ff_fast_malloc(ptr, size, min_size, 0);
> > >  }
> > >  
> > > +void av_memcpynt(void *dst, const void *src, size_t size, int cpu_flags)
> > > +{
> > > +#if ARCH_X86
> > > +    ff_memcpynt_x86(dst, src, size, cpu_flags);
> > > +#else
> > > +    memcpy(dst, src, size, cpu_flags);
> > > +#endif
> > > +}
> > 
> > Alternatively, what about something like:
> > 
> > av_memcpynt_fn av_memcpynt_get_fn(void);
> > 
> > modeled after av_pixelutils_get_sad_fn()? This would skip the need for
> > a wrapper calling the right function.
> 

> I don't see much value in this, unless determining the right function
> causes too much overhead.

I see two advantages, 1. no branch and function call when the function
is called, 2. the cpu_flags must not be passed around, so it's somehow
safer.

I have no strong preference though, updated (untested patch) in
attachment.
-- 
FFmpeg = Fierce and Forgiving Merciless Powered Extroverse Gargoyle
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