[FFmpeg-devel] Performances improvement in "image_copy_plane"

[Timo Rothenpieler]

On 13.07.2022 11:38, Marco Vianini wrote:
>   You can get a very big improvement of performances in the special (but very likely) case of: "(dst_linesize == bytewidth && src_linesize == bytewidth)"

Isn't all that matters dst_linesize == src_linesize, and then you can 
memcpy() the whole plane?

> 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
> Marco Vianini

That code is mangled by your mail client and practically unreadable.