Hi Vitaly, On Thu, Sep 10, 2020 at 01:09:03PM -0400, Vitaly Prosyak wrote: > On 2020-09-10 6:56 a.m., Laurent Pinchart wrote: > > On Thu, Sep 10, 2020 at 01:28:03PM +0300, Pekka Paalanen wrote: > >> On Thu, 10 Sep 2020 12:30:09 +0300 Laurentiu Palcu wrote: > >>> On Thu, Sep 10, 2020 at 11:50:26AM +0300, Pekka Paalanen wrote: > >>>> On Thu, 10 Sep 2020 09:52:26 +0200 Daniel Vetter wrote: > >>>>> On Thu, Sep 10, 2020 at 10:25:43AM +0300, Pekka Paalanen wrote: > >>>>>> On Wed, 9 Sep 2020 13:57:28 +0300 Laurentiu Palcu wrote: > >>>>>> > >>>>>>> Hi all, > >>>>>>> > >>>>>>> I was wondering whether you could give me an advise on how to proceed further > >>>>>>> with the following issue as I'm preparing to upstream the next set of patches > >>>>>>> for the iMX8MQ display controller(DCSS). The display controller has 3 planes, > >>>>>>> each with 2 CSCs and one degamma LUT. The CSCs are in front and after the LUT > >>>>>>> respectively. Then the output from those 3 pipes is blended together and then > >>>>>>> gamma correction is applied using a linear-to-nonlinear LUT and another CSC, if > >>>>>>> needed. > >>>> > >>>> Hi, > >>>> > >>>> hmm, so FB -> CSC -> LUT -> CSC -> blending? > >>>> > >>>> Is it then > >>>> blending -> LUT -> CSC -> encoder > >>>> or > >>>> blending -> CSC -> LUT -> encoder? > >>> > >>> The DCSS pipeline topology is this: > >>> > >>> FB1->CSC_A->LUT->CSC_B-\ > >>> FB2->CSC_A->LUT->CSC_B-|-blender->LUT->CSC_O->encoder > >>> FB3->CSC_A->LUT->CSC_B-/ > >>> > >>> Basically, CSC_A is used to convert to a common colorspace if needed > >>> (YUV->RGB) as well as to perform pixel range conversions: limited->full. > >>> CSC_B is for gamut conversions(like 709->2020). The CSC_O is used to > >>> convert to the colorspace used by the output (like RGB->YUV). > >> > >> I didn't realize that it would be correct to do RGB-YUV conversion in > >> non-linear space, but yeah, that's what most software do too I guess. > >> > >>>> Are all these LUTs per-channel 1D LUTs or something else? > >>> > >>> LUTs are 3D, per pixel component. > >> > >> Sorry, which one? > >> > >> An example of a 3D LUT is 32x32x32 entries with each entry being a > >> triplet, while a 1D LUT could be 1024 entries with each entry being a > >> scalar. 1D LUTs are used per-channel so you need three of them, 3D LUTs > >> you need just one for the color value triplet mapping. > >> > >> A 3D LUT can express much more than a 4x4 CTM. A 1D LUT cannot do the > >> channel mixing that a CTM can. > >> > >> So if you truly have 3D LUTs everywhere, I wonder why the CSC matrix > >> blocks exist... > > > > Possibly because the 3D LUT uses interpolation (it's a 17x17x17 LUT in > > R-Car), having a separate CSC can give more precision (as well as > > allowing the two problems to be decoupled, at a relatively low hardware > > cost). > > If you put nonlinear signal to 3DLUT then your > precision would be improved. > How many bits each color value has in 3DLUT ? The whole display pipeline uses 8 bits per component. -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
