[FFmpeg-devel] [PATCH 1/2] libswscale/x86/yuv2rgb: Change inline assembly into nasm code

[Fu, Ting]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Carl
> Eugen Hoyos
> Sent: Monday, December 2, 2019 05:49 PM
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 1/2] libswscale/x86/yuv2rgb: Change inline
> assembly into nasm code
> 
> Am Mo., 2. Dez. 2019 um 04:17 Uhr schrieb Fu, Ting <ting.fu at intel.com>:
> >
> >
> >
> > > -----Original Message-----
> > > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> > > Michael Niedermayer
> > > Sent: Friday, November 29, 2019 05:33 AM
> > > To: FFmpeg development discussions and patches
> > > <ffmpeg-devel at ffmpeg.org>
> > > Subject: Re: [FFmpeg-devel] [PATCH 1/2] libswscale/x86/yuv2rgb:
> > > Change inline assembly into nasm code
> > >
> > > On Thu, Nov 28, 2019 at 02:07:07PM +0800, Ting Fu wrote:
> > > > Signed-off-by: Ting Fu <ting.fu at intel.com>
> > > > ---
> > > >  libswscale/x86/Makefile           |   1 +
> > > >  libswscale/x86/swscale.c          |  16 +-
> > > >  libswscale/x86/yuv2rgb.c          |  81 ++----
> > > >  libswscale/x86/yuv2rgb_template.c | 441 ++++++------------------------
> > > >  libswscale/x86/yuv_2_rgb.asm      | 270 ++++++++++++++++++
> > > >  5 files changed, 394 insertions(+), 415 deletions(-)  create mode
> > > > 100644 libswscale/x86/yuv_2_rgb.asm
> > >
> > > This changes the output, i presume that is unintentional
> > >
> > > ./ffmpeg -cpuflags 0 -i matrixbench_mpeg2.mpg -t 1 -vf
> > > format=yuv420p,format=rgb565le -an -f framecrc -
> > >
> > > 0,          0,          0,        1,   829440, 0x1bd78b86
> > > 0,          1,          1,        1,   829440, 0x85910b33
> > > ...
> > > vs.
> > > 0,          0,          0,        1,   829440, 0x31f4a2bd
> > > 0,          1,          1,        1,   829440, 0xf0c66218
> > > ...
> > >
> > >
> >
> > Hi Michael,
> >
> > This unexpected change is because of the missing verify of current SIMD
> support.
> > So, when cpuflag=0, ffmpeg used mmx code to compute as default.
> > I added if (EXTERNAL_XXX(cpu_flags)) to verify the SIMD in
> libswscale/x86/yuv2rgb.c.
> 
> Could the patch be split to make this change easier to understand?

Hi Carl,

I didn’t come across any good idea to separate the PATCH. 
Since the [PATCH 1/2] is consisted of mmx code for yuv2rgb24/bgr24/rgb32/bgr32/rgb15/rgb16 and they're all come from former inline assembly.
Should it be separated into something like 
PATCH 1: mmx yuv2rgb24/bgr24
PATCH 2: mmx yuv2rgb32/bgr32
PATCH 3: mmx yuv2rgb15/rgb16
Or adding more comments in nasm file would be more helpful?

Can you show me if there is any better solution? I cannot be more grateful to it.

Thank you,
Ting Fu

> 
> Carl Eugen
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