Re: [FFmpeg-devel] [PATCH] Request for adding XPSNR avfilter

[Paul B Mahol <onemda@gmail.com>]

On 1/11/23, Helmrich, Christian <christian.helmrich@hhi.fraunhofer.de> wrote:
> Hi,
>
>
>> So its better to use that instead of human written assembly? Does clang
>> generate faster code without this asm?
>
>
> I'm not sure I fully understand your questions, but I hope the following
> answers it. The reason why we auto-converted our intrinsics code to asm is
> not a technical one, we unfortunately just don't have the knowledge or
> resources to manually write asm code. If I remember correctly, the SIMD
> optimized code runs about twice as fast as the C code, especially on UHD
> input.

Compare clang compiled ffmpeg without this asm code and with it, and
tell if any difference.
I'might do it anyway later.

>
>
>> Please remove SLICE_THREADS related flag as there is no call to execute to
>> filter in slices. Please remove stdbool.h header and adapt code to compile
>> without it.
>
>
> Done, please find attached a second version (v1) of the XPSNR avfilter
> patch.
>
>
> Thanks and best,
>
>
> Christian Helmrich
>
> Fraunhofer HHI, Video Coding and Analytics Department
>
>
> ________________________________
> Von: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> im Auftrag von Paul B
> Mahol <onemda@gmail.com>
> Gesendet: Dienstag, 10. Januar 2023 21:43
> An: FFmpeg development discussions and patches
> Cc: Stoffers, Christian
> Betreff: Re: [FFmpeg-devel] [PATCH] Request for adding XPSNR avfilter
>
> On 1/10/23, Helmrich, Christian <christian.helmrich@hhi.fraunhofer.de>
> wrote:
>> Hi,
>>
>> please find attached a patch (relative to FFmpeg master as of early
>> January
>> 10, 2023)
>> adding avfilter support for extended perceptually weighted peak
>> signal-to-noise ratio
>> (XPSNR) measurements for videos, as described in the related addition to
>> filters.texi.
>>
>> The XPSNR code was originally vectorized using SIMD intrinsics, but we
>> concluded that
>> FFmpeg code requires asm instead of such intrinsics, so we let gcc
>> auto-convert these
>
> So its better to use that instead of human written assembly?
> Does clang generate faster code without this asm?
>
>> instructions to pure assembly; see the vf_xpsnr.asm file. If the added
>> asm
>> code is too
>> lengthy, intrinsics would be possible, or something else is missing,
>> please
>> let us know.
>>
>
> Please remove SLICE_THREADS related flag as there is no call to
> execute to filter in slices.
> Please remove stdbool.h header and adapt code to compile without it.
>
>> Best,
>>
>> Christian Helmrich and Christian Stoffers
>> Fraunhofer HHI
>>
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