Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Mon, 10 Jun 2019 at 23:02, Lauri Kasanen wrote: > On Mon, 10 Jun 2019 17:42:00 -0700 > Adrian Tong wrote: > > > I have been trying to implement yuv420_to_bgr24 using SSE2 instruction. I > > ran into the case where the output of C implemented yuv420_to_bgr24 has > > slightly different resulting bgr24 image from MMX implemented > > yuv420_to_bgr24. Is this expected behavior ? > > Yes, some of the MMX implementations choose speed over accuracy, I ran > to that myself when doing PPC versions. For a SSE version, if an > accurate version is fast enough, please try to match the C version. > Otherwise try to match MMX. > Thanks for confirming, Lauri. I am reading the MMX code for YUV420 to BGR24, I am a little bit confused by it. Particularly, we shift left by 3 bits (multiply by 8) for better precision. How does this increase precision ? Also, the conversion formula has some floating point numbers as coefficient, But we are doing integer type multiplication here. https://github.com/FFmpeg/FFmpeg/blob/master/libswscale/x86/yuv2rgb_template.c#L92 Thanks - Adrian > > - Lauri > ___ > 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". ___ 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".
Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Mon, 10 Jun 2019 17:42:00 -0700 Adrian Tong wrote: > I have been trying to implement yuv420_to_bgr24 using SSE2 instruction. I > ran into the case where the output of C implemented yuv420_to_bgr24 has > slightly different resulting bgr24 image from MMX implemented > yuv420_to_bgr24. Is this expected behavior ? Yes, some of the MMX implementations choose speed over accuracy, I ran to that myself when doing PPC versions. For a SSE version, if an accurate version is fast enough, please try to match the C version. Otherwise try to match MMX. - Lauri ___ 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".
Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Sat, 8 Jun 2019 at 09:42, Adrian Tong wrote: > > > On Sat, 8 Jun 2019 at 09:38, Lauri Kasanen wrote: > >> On Sat, 8 Jun 2019 06:51:51 -0700 >> Adrian Tong wrote: >> >> > Hi Lauri. >> > >> > Thanks for the reply, any reason why this has not been implemented >> before ? >> > it seems to me that this would be a pretty important/hot function. >> >> Just the usual, nobody has had the interest. There are other places too >> where the only x86 accel is mmx. >> >> - Lauri >> > > I see. Thank you. I will see what I can do. > -Adrian > I have been trying to implement yuv420_to_bgr24 using SSE2 instruction. I ran into the case where the output of C implemented yuv420_to_bgr24 has slightly different resulting bgr24 image from MMX implemented yuv420_to_bgr24. Is this expected behavior ? Thanks -Adrian > ___ >> 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". > > ___ 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".
Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Sat, 8 Jun 2019 at 09:38, Lauri Kasanen wrote: > On Sat, 8 Jun 2019 06:51:51 -0700 > Adrian Tong wrote: > > > Hi Lauri. > > > > Thanks for the reply, any reason why this has not been implemented > before ? > > it seems to me that this would be a pretty important/hot function. > > Just the usual, nobody has had the interest. There are other places too > where the only x86 accel is mmx. > > - Lauri > I see. Thank you. I will see what I can do. -Adrian > ___ > 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". ___ 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".
Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Sat, 8 Jun 2019 06:51:51 -0700 Adrian Tong wrote: > Hi Lauri. > > Thanks for the reply, any reason why this has not been implemented before ? > it seems to me that this would be a pretty important/hot function. Just the usual, nobody has had the interest. There are other places too where the only x86 accel is mmx. - Lauri ___ 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".
Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Fri, 7 Jun 2019 at 23:20, Lauri Kasanen wrote: > On Fri, 7 Jun 2019 08:38:35 -0700 > Adrian Tong wrote: > > > Hi > > > > I have a workload which spends a significant amount of time (~10%) in > > the yuv420_bgr24_mmxext function in FFMEPG. > > > > I looked at the assembly and profile and see MMX (64 bit) registers are > > used. I wonder whether we can have a SSE2 version which has a register > bit > > width of 128. > > > > I am very interested in implementing such support if it is possible. > > I'm not well versed in x86 vectors, so I can't say if SSE2 is enough or > some other SSE version would be needed, but certainly YUV to RGB > conversion can be done faster than with MMX. Please do send a patch. > > - Lauri > Hi Lauri. Thanks for the reply, any reason why this has not been implemented before ? it seems to me that this would be a pretty important/hot function. -Adrian > ___ > 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". ___ 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".
Re: [FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
On Fri, 7 Jun 2019 08:38:35 -0700 Adrian Tong wrote: > Hi > > I have a workload which spends a significant amount of time (~10%) in > the yuv420_bgr24_mmxext function in FFMEPG. > > I looked at the assembly and profile and see MMX (64 bit) registers are > used. I wonder whether we can have a SSE2 version which has a register bit > width of 128. > > I am very interested in implementing such support if it is possible. I'm not well versed in x86 vectors, so I can't say if SSE2 is enough or some other SSE version would be needed, but certainly YUV to RGB conversion can be done faster than with MMX. Please do send a patch. - Lauri ___ 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".
[FFmpeg-devel] yuv420_bgr24_mmxext conversion taking significant time
Hi I have a workload which spends a significant amount of time (~10%) in the yuv420_bgr24_mmxext function in FFMEPG. I looked at the assembly and profile and see MMX (64 bit) registers are used. I wonder whether we can have a SSE2 version which has a register bit width of 128. I am very interested in implementing such support if it is possible. Thanks -Adrian ___ 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".
