[FFmpeg-devel] Performances improvement in "image_copy_plane"

[Marco Vianini]

 I did following tests on Windows 10 64bit.I compiled code in Release.
I copied my pc camera frames 1000 times (resolution 1920x1080):
With Coalesce (MY PATCH):copy_cnt=100  size=1920x1080 tot_time_copy(us)=36574 (average=365.74)copy_cnt=200  size=1920x1080 tot_time_copy(us)=78207 (average=391.035)copy_cnt=300  size=1920x1080 tot_time_copy(us)=122170(average=407.233)copy_cnt=400  size=1920x1080 tot_time_copy(us)=163678(average=409.195)copy_cnt=500  size=1920x1080 tot_time_copy(us)=201872(average=403.744)copy_cnt=600  size=1920x1080 tot_time_copy(us)=246174(average=410.29)copy_cnt=700  size=1920x1080 tot_time_copy(us)=287043(average=410.061)copy_cnt=800  size=1920x1080 tot_time_copy(us)=326462(average=408.077)copy_cnt=900  size=1920x1080 tot_time_copy(us)=356882(average=396.536)copy_cnt=1000 size=1920x1080 tot_time_copy(us)=394566(average=394.566)
Without Coalesce:copy_cnt=100  size=1920x1080 tot_time_copy(us)=44303 (average=443.03)copy_cnt=200  size=1920x1080 tot_time_copy(us)=100501(average=502.505)copy_cnt=300  size=1920x1080 tot_time_copy(us)=150097(average=500.323)copy_cnt=400  size=1920x1080 tot_time_copy(us)=201010(average=502.525)copy_cnt=500  size=1920x1080 tot_time_copy(us)=256818(average=513.636)copy_cnt=600  size=1920x1080 tot_time_copy(us)=303273(average=505.455)copy_cnt=700  size=1920x1080 tot_time_copy(us)=359152(average=513.074)copy_cnt=800  size=1920x1080 tot_time_copy(us)=414413(average=518.016)copy_cnt=900  size=1920x1080 tot_time_copy(us)=465315(average=517.017)copy_cnt=1000 size=1920x1080 tot_time_copy(us)=520381(average=520.381)
I think the results are very good.What do you think about?
Thank You


    Il mercoledì 13 luglio 2022 11:52:23 CEST, Paul B Mahol <onemda at gmail.com> ha scritto:  
 
 On Wed, Jul 13, 2022 at 11:38 AM Marco Vianini <
marco_vianini-at-yahoo.it at ffmpeg.org> wrote:

>  You can get a very big improvement of performances in the special (but
> very likely) case of: "(dst_linesize == bytewidth && src_linesize ==
> bytewidth)"
>
> In this case in fact We can "Coalesce rows", that is using ONLY ONE
> MEMCPY, instead of a smaller memcpy for every row (that is looping for
> height times).
>
> Code:"static void image_copy_plane(uint8_t      *dst, ptrdiff_t
> dst_linesize,                            const uint8_t *src, ptrdiff_t
> src_linesize,                            ptrdiff_t bytewidth, int
> height){    if (!dst || !src)        return;
> av_assert0(abs(src_linesize) >= bytewidth);    av_assert0(abs(dst_linesize)
> >= bytewidth); // MY PATCH START    // Coalesce rows.    if (dst_linesize
> == bytewidth && src_linesize == bytewidth) {      bytewidth *= height;
> height = 1;      src_linesize = dst_linesize = 0;    }// MY PATCH STOP
>    for (;height > 0; height--) {        memcpy(dst, src, bytewidth);
>  dst += dst_linesize;        src += src_linesize;    }}"
> What do You think about?Thank You
>

Show the benchmark numbers.


> Marco Vianini
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