[Intel-gfx] [PATCH] drm/i915/icl: Handle YCbCr to RGB conversion for BT2020 case

[Shankar, Uma]

>-----Original Message-----
>From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
>Sent: Thursday, May 9, 2019 8:28 PM
>To: Shankar, Uma <uma.shankar at intel.com>
>Cc: Sharma, Shashank <shashank.sharma at intel.com>; intel-
>gfx at lists.freedesktop.org
>Subject: Re: [Intel-gfx] [PATCH] drm/i915/icl: Handle YCbCr to RGB conversion for
>BT2020 case
>
>On Thu, May 09, 2019 at 02:54:19PM +0000, Shankar, Uma wrote:
>>
>>
>> >-----Original Message-----
>> >From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
>> >Sent: Tuesday, May 7, 2019 9:08 PM
>> >To: Shankar, Uma <uma.shankar at intel.com>
>> >Cc: Sharma, Shashank <shashank.sharma at intel.com>; intel-
>> >gfx at lists.freedesktop.org
>> >Subject: Re: [Intel-gfx] [PATCH] drm/i915/icl: Handle YCbCr to RGB
>> >conversion for
>> >BT2020 case
>> >
>> >On Tue, May 07, 2019 at 02:35:15PM +0000, Shankar, Uma wrote:
>> >>
>> >>
>> >> >-----Original Message-----
>> >> >From: Intel-gfx [mailto:intel-gfx-bounces at lists.freedesktop.org]
>> >> >On Behalf Of Ville Syrjälä
>> >> >Sent: Tuesday, May 7, 2019 7:37 PM
>> >> >To: Sharma, Shashank <shashank.sharma at intel.com>
>> >> >Cc: intel-gfx at lists.freedesktop.org
>> >> >Subject: Re: [Intel-gfx] [PATCH] drm/i915/icl: Handle YCbCr to RGB
>> >> >conversion for
>> >> >BT2020 case
>> >> >
>> >> >On Tue, May 07, 2019 at 06:32:57PM +0530, Shashank Sharma wrote:
>> >> >> From: Uma Shankar <uma.shankar at intel.com>
>> >> >>
>> >> >> Currently input csc for YCbCR to RGB conversion handles only
>> >> >> BT601 and Bt709. Extending it to support BT2020 as well.
>> >> >>
>> >> >> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>> >> >> Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
>> >> >> ---
>> >> >>  drivers/gpu/drm/i915/intel_sprite.c | 24
>> >> >> ++++++++++++++++++++++++
>> >> >>  1 file changed, 24 insertions(+)
>> >> >>
>> >> >> diff --git a/drivers/gpu/drm/i915/intel_sprite.c
>> >> >> b/drivers/gpu/drm/i915/intel_sprite.c
>> >> >> index 44aaeac1b2ed..2536e757bec2 100644
>> >> >> --- a/drivers/gpu/drm/i915/intel_sprite.c
>> >> >> +++ b/drivers/gpu/drm/i915/intel_sprite.c
>> >> >> @@ -433,6 +433,18 @@ icl_program_input_csc(struct intel_plane *plane,
>> >> >>  			0x9EF8, 0x7800, 0xABF8,
>> >> >>  			0x0, 0x7800,  0x7ED8,
>> >> >>  		},
>> >> >> +		/*
>> >> >> +		 * BT.2020 full range YCbCr -> full range RGB
>> >> >> +		 * The matrix required is :
>> >> >> +		 * [1.000, 0.000, 1.474,
>> >> >> +		 *  1.000, -0.1645, -0.5713,
>> >> >> +		 *  1.000, 1.8814, 0.0000]
>> >> >> +		 */
>> >> >> +		[DRM_COLOR_YCBCR_BT2020] = {
>> >> >> +			0x7BC8, 0x7800, 0x0,
>> >> >> +			0x8928, 0x7800, 0xAA88,
>> >> >> +			0x0, 0x7800, 0x7F10,
>> >> >> +		},
>> >> >>  	};
>> >> >>
>> >> >>  	/* Matrix for Limited Range to Full Range Conversion */ @@
>> >> >> -461,6
>> >> >> +473,18 @@ icl_program_input_csc(struct intel_plane *plane,
>> >> >>  			0x8888, 0x7918, 0xADA8,
>> >> >>  			0x0, 0x7918,  0x6870,
>> >> >>  		},
>> >> >> +		/*
>> >> >> +		 * BT.2020 Limited range YCbCr -> full range RGB
>> >> >> +		 * The matrix required is :
>> >> >> +		 * [1.164, 0.000, 1.717,
>> >> >> +		 *  1.138, -0.1873, -0.6504,
>> >> >> +		 *  1.1380, 2.1417, 0.0000]
>> >> >
>> >> >Where are those 1.138 coming from?
>> >>
>> >> Hi Ville,
>> >> This is the original YCBCR to RGB BT2020 matrix:
>> >> {
>> >>         1.00000000000,  0.00000000000,  1.47460000000,
>> >>         1.00000000000,  -0.16455312684, -0.57135312684,
>> >>         1.00000000000,  1.88140000000,  0.00000000000 };
>> >>
>> >> We have to convert Limited Range YCbCr to Full Range RGB. Hence we
>> >> need to
>> >apply a scale factor:
>> >>  yscalefactor = 219.0 * normalizingfactor;  cbcrscalefactor = 224.0
>> >> * normalizingfactor;
>> >>
>> >>  /* Scale factors are inverted for LR to FR conversion */
>> >> yscalefactor = 1.0 / yscalefactor;  cbcrscalefactor = 1.0 /
>> >> cbcrscalefactor;
>> >>
>> >> This yields the above results.
>> >
>> >Those are the coefficients for Y, so they should still be the same
>> >for all three output channels.
>> >
>> >igt_color_encoding gives me:
>> >|1.1644, 0.0000, 1.6787,|
>> >|1.1644,-0.1873,-0.6504,|
>> >|1.1644, 2.1418, 0.0000,|
>>
>> Ok, I used the igt_color_encoding method and able to get values what you got.
>> Will update the matrix. Thanks Ville.
>>
>> >Looks like we're also misprogramming the Y pre-offset for the full range YCbCr
>case.
>> For full range, I am getting same values as programmed above. Looks ok, can you
>double check.
>
>The matrix itself looks OK (some minor rounding differences perhaps, but nothing
>major). But the Y preoffset should be zero for full range YCbCr.

Hi Ville,
This is what I got for Full Range from igt_color_encoding.
m4.d[m(row=0, col=0)] = 1.000000
m4.d[m(row=1, col=0)] = 1.000000
m4.d[m(row=2, col=0)] = 1.000000
m4.d[m(row=3, col=0)] = 0.000000
m4.d[m(row=0, col=1)] = 0.000000
m4.d[m(row=1, col=1)] = -0.164553
m4.d[m(row=2, col=1)] = 1.881400
m4.d[m(row=3, col=1)] = 0.000000
m4.d[m(row=0, col=2)] = 1.474600
m4.d[m(row=1, col=2)] = -0.571353
m4.d[m(row=2, col=2)] = 0.000000
m4.d[m(row=3, col=2)] = 0.000000
m4.d[m(row=0, col=3)] = -188.748810
m4.d[m(row=1, col=3)] = 94.195992
m4.d[m(row=2, col=3)] = -240.819199
m4.d[m(row=3, col=3)] = 1.000000

which matches our table. This is the argument list for :
struct igt_mat4 m4 = igt_ycbcr_to_rgb_matrix(DRM_FORMAT_YUV420,
                                     DRM_FORMAT_XRGB8888,
                                       IGT_COLOR_YCBCR_BT2020,
                                       IGT_COLOR_YCBCR_FULL_RANGE);

Am I am missing something ?

Regards,
Uma Shankar
>Ville Syrjälä
>Intel