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

Carl Eugen Hoyos ceffmpeg at gmail.com
Tue Dec 3 10:22:43 EET 2019


Am Di., 3. Dez. 2019 um 04:53 Uhr schrieb Fu, Ting <ting.fu at intel.com>:
>
>
>
> > -----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.

I didn't want to imply that I know of a better way, just that your answer to
Michael's question made me wonder if adding EXTERNAL_XXX() in a
separate patch would fix his concern.

Carl Eugen


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