On Fri, May 31, 2019 at 2:17 PM Paul B Mahol <one...@gmail.com> wrote: > > On 5/31/19, Pavel Koshevoy <pkoshe...@gmail.com> wrote: > > On Fri, May 31, 2019 at 2:03 PM Paul B Mahol <one...@gmail.com> wrote: > >> > >> On 5/31/19, Pavel Koshevoy <pkoshe...@gmail.com> wrote: > >> > On Fri, May 31, 2019 at 1:44 PM Pavel Koshevoy <pkoshe...@gmail.com> > >> > wrote:
<snip> > >> >> I've had to use zscale to convert 10-bit 4k60p video from HLG HDR to > >> >> SDR > >> >> (bt709). It was ~36x times slower than real time. What I ended up > >> >> doing > >> >> to speed it up was to generate CLUT image (16-bit yuv444 65x65x65 > >> >> sampling > >> >> of input color space), lay it out as a 2D image (512x537), and run it > >> >> through zscale to generate the HDR->SDR transform CLUT. Then I used > >> >> the > >> >> CLUT instead of zscale for every frame... that got me to about ~3.5x > >> >> times slower than realtime converting 60fps 10-bit 4k HLG to SDR (and > >> >> I > >> >> don't know any assembly, so I didn't attempt to optimize the CLUT > >> >> trilinear optimization with SIMD, so maybe it could be faster still). > >> >> I > >> >> then ported to CUDA and was able to convert 4k60p HLG->SDR faster than > >> >> realtime on a Pascal GPU. > >> >> > >> > > >> > I meant trilinear interpolation > >> > > >> > > >> >> So, I'm not sure that adding slice threading to zscale is the best > >> >> optimization for it. I think capturing the effect of zscale in a CLUT > >> >> would be a more significant optimization. > >> >> > >> >> Just my 2 cents, hope this helps. > >> > >> Your logic is completely flawed. > >> You can not rescale images with LUT tables. > > > > > > I was not resizing the image from 4K to 1080p ... the output was till > > 4K. I was converting from 10-bit in whatever HDR input colorspace > > (HLG, or HDR10), to 8-bit SDR output colorspace. You most definitely > > can approximate that transformation with a CLUT. > > > > Seen lut3d filter? lut3d works with RGB images, my input and output are all YUV (P010 actually) also, lut3d requires a file parameter, not great for my use case. I could generate a CLUT with zscale and dump it to disk so I could initialize lut3d with it, but I hope you see how inconvenient that is from API view point. > > Since zscale is capable of resizing and colorspace conversion -- > > perhaps this functionality should be split into separate filters so > > each can be otpimized differently. > > You logic is completely flawed yet again. > zscale is wrapper around another library. I know, zimg, C++11. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
