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

[Shankar, Uma]

>-----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. 

Regards,
Uma Shankar

>> +		 */
>> +		[DRM_COLOR_YCBCR_BT2020] = {
>> +			0x7DC0, 0x7950, 0x0,
>> +			0x8A68, 0x7918, 0xAC00,
>> +			0x0, 0x7918, 0x6890,
>> +		},
>>  	};
>>  	const u16 *csc;
>>
>> --
>> 2.17.1
>>
>> _______________________________________________
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>> Intel-gfx at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>--
>Ville Syrjälä
>Intel
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