[FFmpeg-devel] swscale/input : avoid float calc for GrayFloat to Gray16 conv

[Martin Vignali]

> > ---
> >  libswscale/input.c            | 10 +++++-----
> >  libswscale/swscale_internal.h | 20 ++++++++++++++++++++
> >  2 files changed, 25 insertions(+), 5 deletions(-)
>
> please provide benchmark, what is the impact on speed from this ?
>
>
In my tests, the patch increase speed by around 20%.

Test with this sample (UHD Gray float PSD file) : https://we.tl/t-Ty9hR20gUw

And this command line (test the bswap func : grayf32ToY16_bswap_c)
./ffmpeg -benchmark -loop 1 -t 30 -i TEST_PSD_GRAY_00000.psd -pix_fmt
gray16be -f null -

Without the patch : (using float calc)
frame=  750 fps= 23 q=-0.0 Lsize=N/A time=00:00:30.00 bitrate=N/A
speed=0.909x
bench: utime=26.577s stime=10.061s rtime=33.063s
bench: maxrss=697888768kB


With the patch : (not use float calc)
frame=  750 fps= 27 q=-0.0 Lsize=N/A time=00:00:30.00 bitrate=N/A
speed=1.07x
bench: utime=21.512s stime=10.136s rtime=27.992s
bench: maxrss=697942016kB

Martin