[FFmpeg-devel] [PATCH v3 2/5] avcodec/v210enc: make 8bit and 10bit function consistent

[Michael Niedermayer]

On Sun, Sep 01, 2019 at 09:20:20PM +0800, lance.lmwang at gmail.com wrote:
> From: Limin Wang <lance.lmwang at gmail.com>
> 
> I have benchmarked the performance with c code and haven't see any
> performance impact.
> 
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
>  libavcodec/v210enc.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/libavcodec/v210enc.c b/libavcodec/v210enc.c
> index 1b840b2..69a2efe 100644
> --- a/libavcodec/v210enc.c
> +++ b/libavcodec/v210enc.c
> @@ -43,12 +43,7 @@ static void v210_planar_pack_8_c(const uint8_t *y, const uint8_t *u,
>      uint32_t val;
>      int i;
>  
> -    /* unroll this to match the assembly */
> -    for (i = 0; i < width - 11; i += 12) {
> -        WRITE_PIXELS(u, y, v, 8);
> -        WRITE_PIXELS(y, u, y, 8);
> -        WRITE_PIXELS(v, y, u, 8);
> -        WRITE_PIXELS(y, v, y, 8);
> +    for (i = 0; i < width - 5; i += 6) {
>          WRITE_PIXELS(u, y, v, 8);
>          WRITE_PIXELS(y, u, y, 8);
>          WRITE_PIXELS(v, y, u, 8);

I have retested this with START/STOP_TIMER
and the more unrolled loop is consistently faster

./ffmpeg -cpuflags 0 -v 99 -i matrixbench_mpeg2.mpg -vcodec v210 -an test.avi

 31620 decicycles in TEST, 2096691 runs,    461 skips  0  0  0  0  0  0  0  0  0  0  0 21 13  9  8  7  8  7  0  0  0  0  0  0  0  0  0  0  0  0  0  0
 31509 decicycles in TEST, 2096892 runs,    260 skips  0  0  0  0  0  0  0  0  0  0  0 21 10  9  8  6  7  3  2  0  0  0  0  0  0  0  0  0  0  0  0  0
 32069 decicycles in TEST, 2096965 runs,    187 skips  0  0  0  0  0  0  0  0  0  0  0 21 16 10  8  6  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
 31522 decicycles in TEST, 2096962 runs,    190 skips  0  0  0  0  0  0  0  0  0  0  0 21 10  9  8  6  1  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
 31537 decicycles in TEST, 2096784 runs,    368 skips  0  0  0  0  0  0  0  0  0  0  0 21 12  8  9  7  7  7  0  0  0  0  0  0  0  0  0  0  0  0  0  0

prev:
 30705 decicycles in TEST, 2096875 runs,    277 skips  0  0  0  0  0  0  0  0  0  0  0 21 15  9  9  7  5  3  1  0  0  0  0  0  0  0  0  0  0  0  0  0
 30771 decicycles in TEST, 2096907 runs,    245 skips  0  0  0  0  0  0  0  0  0  0  0 21 15  9  8  6  7  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
 30560 decicycles in TEST, 2096904 runs,    248 skips  0  0  0  0  0  0  0  0  0  0  0 21 10  9  9  6  2  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
 31020 decicycles in TEST, 2096974 runs,    178 skips  0  0  0  0  0  0  0  0  0  0  0 21 16  9  8  6  2  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0
 31018 decicycles in TEST, 2096980 runs,    172 skips  0  0  0  0  0  0  0  0  0  0  0 21 16  9  8  6  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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