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From: Harry Wentland <harry.wentland@amd.com>
To: Pekka Paalanen <pekka.paalanen@collabora.com>
Cc: Sebastian Wick <sebastian.wick@redhat.com>,
	kernel-dev@igalia.com, Shashank Sharma <Shashank.Sharma@amd.com>,
	sunpeng.li@amd.com, Simon Ser <contact@emersion.fr>,
	Xinhui.Pan@amd.com, Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
	Xaver Hugl <xaver.hugl@gmail.com>,
	dri-devel@lists.freedesktop.org,
	Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>,
	Melissa Wen <mwen@igalia.com>, Alex Hung <alex.hung@amd.com>,
	amd-gfx@lists.freedesktop.org, daniel@ffwll.ch,
	Alex Deucher <alexander.deucher@amd.com>,
	airlied@gmail.com, christian.koenig@amd.com,
	Joshua Ashton <joshua@froggi.es>,
	sungjoon.kim@amd.com
Subject: Re: [PATCH v3 07/32] drm/amd/display: document AMDGPU pre-defined transfer functions
Date: Fri, 29 Sep 2023 09:08:41 -0400	[thread overview]
Message-ID: <2f22c6fa-3b88-4401-a77a-6dc97115a045@amd.com> (raw)
In-Reply-To: <20230929103522.5635c48b.pekka.paalanen@collabora.com>



On 2023-09-29 03:35, Pekka Paalanen wrote:
> On Thu, 28 Sep 2023 16:16:57 -0400
> Harry Wentland <harry.wentland@amd.com> wrote:
> 
>> On 2023-09-25 15:49, Melissa Wen wrote:
>>> Brief documentation about pre-defined transfer function usage on AMD
>>> display driver and standardized EOTFs and inverse EOTFs.
>>>
>>> v3:
>>> - Document BT709 OETF (Pekka)
>>> - Fix description of sRGB and pure power funcs (Pekka)
>>>
>>> Co-developed-by: Harry Wentland <harry.wentland@amd.com>
>>> Signed-off-by: Harry Wentland <harry.wentland@amd.com>
>>> Signed-off-by: Melissa Wen <mwen@igalia.com>
>>> ---
>>>  .../amd/display/amdgpu_dm/amdgpu_dm_color.c   | 39 +++++++++++++++++++
>>>  1 file changed, 39 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
>>> index d03bdb010e8b..14f9c02539c6 100644
>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_color.c
>>> @@ -85,6 +85,45 @@ void amdgpu_dm_init_color_mod(void)
>>>  }
>>>  
>>>  #ifdef AMD_PRIVATE_COLOR
>>> +/* Pre-defined Transfer Functions (TF)
>>> + *
>>> + * AMD driver supports pre-defined mathematical functions for transferring
>>> + * between encoded values and optical/linear space. Depending on HW color caps,
>>> + * ROMs and curves built by the AMD color module support these transforms.
>>> + *
>>> + * The driver-specific color implementation exposes properties for pre-blending
>>> + * degamma TF, shaper TF (before 3D LUT), and blend(dpp.ogam) TF and
>>> + * post-blending regamma (mpc.ogam) TF. However, only pre-blending degamma
>>> + * supports ROM curves. AMD color module uses pre-defined coefficients to build
>>> + * curves for the other blocks. What can be done by each color block is
>>> + * described by struct dpp_color_capsand struct mpc_color_caps.
>>> + *
>>> + * AMD driver-specific color API exposes the following pre-defined transfer
>>> + * functions:
>>> + *
>>> + * - Linear/Unity: linear/identity relationship between pixel value and
>>> + *   luminance value;
>>> + * - Gamma 2.2, Gamma 2.4, Gamma 2.6: pure power functions;
>>> + * - sRGB: 2.4: The piece-wise transfer function from IEC 61966-2-1:1999;
>>> + * - BT.709: has a linear segment in the bottom part and then a power function
>>> + *   with a 0.45 (~1/2.22) gamma for the rest of the range; standardized by
>>> + *   ITU-R BT.709-6;
>>> + * - PQ (Perceptual Quantizer): used for HDR display, allows luminance range
>>> + *   capability of 0 to 10,000 nits; standardized by SMPTE ST 2084.
>>> + *  
>>
>> I think it's important to highlight that the AMD color model is
>> designed with an assumption that SDR (sRGB, BT.709, G2.2, etc.)
>> peak white maps (normalized to 1.0 FP) to 80 nits in the PQ system.
>> This has the implication that PQ EOTF (NL-to-L) maps to [0.0..125.0].
>> 125.0 = 10,000 nits / 80 nits
>>
>> I think we'll want table or some other way describing this:
>>
>> (Using L to mean linear and NL to mean non-linear.)
>>
>> == sRGB, BT709, Gamma 2.x ==
>> NL form is either UNORM or [0.0, 1.0]
>> L form is [0.0, 1.0]
>>
>> Note that HDR multiplier can wide range beyond [0.0, 1.0].
>> In practice this means that PQ TF is needed for any subsequent
>> L-to-NL transforms.
>>
>> == PQ ==
>> NL form is either UNORM or FP16 CCCS (Windows canonical composition color space, see [1])
>> L form is [0.0, 125.0]
> 
> Hi,
> 
> what is [1]?
> 

Oops.

[1] https://learn.microsoft.com/en-us/windows/win32/direct3darticles/high-dynamic-range

Harry

> 
> Thanks,
> pq
> 
>> == Unity, Default ==
>> NL form is either UNORM or FP16 CCCS
>> L form is either [0.0, 1.0] (mapping from UNORM) or CCCS (mapping from CCCS FP16)
>>
>> Harry
>>
>>> + * In the driver-specific API, color block names attached to TF properties
>>> + * suggest the intention regarding non-linear encoding pixel's luminance
>>> + * values. As some newer encodings don't use gamma curve, we make encoding and
>>> + * decoding explicit by defining an enum list of transfer functions supported
>>> + * in terms of EOTF and inverse EOTF, where:
>>> + *
>>> + * - EOTF (electro-optical transfer function): is the transfer function to go
>>> + *   from the encoded value to an optical (linear) value. De-gamma functions
>>> + *   traditionally do this.
>>> + * - Inverse EOTF (simply the inverse of the EOTF): is usually intended to go
>>> + *   from an optical/linear space (which might have been used for blending)
>>> + *   back to the encoded values. Gamma functions traditionally do this.
>>> + */
>>>  static const char * const
>>>  amdgpu_transfer_function_names[] = {
>>>  	[AMDGPU_TRANSFER_FUNCTION_DEFAULT]		= "Default",  
>>
>>
> 


  reply	other threads:[~2023-09-29 13:08 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-25 19:49 [PATCH v3 00/32] drm/amd/display: add AMD driver-specific properties for color mgmt Melissa Wen
2023-09-25 19:49 ` [PATCH v3 01/32] drm/drm_mode_object: increase max objects to accommodate new color props Melissa Wen
2023-09-25 19:49 ` [PATCH v3 02/32] drm/drm_property: make replace_property_blob_from_id a DRM helper Melissa Wen
2023-09-25 19:49 ` [PATCH v3 03/32] drm/drm_plane: track color mgmt changes per plane Melissa Wen
2023-09-25 19:49 ` [PATCH v3 04/32] drm/amd/display: add driver-specific property for plane degamma LUT Melissa Wen
2023-09-25 19:49 ` [PATCH v3 05/32] drm/amd/display: add plane degamma TF driver-specific property Melissa Wen
2023-09-25 19:49 ` [PATCH v3 06/32] drm/amd/display: explicitly define EOTF and inverse EOTF Melissa Wen
2023-09-25 19:49 ` [PATCH v3 07/32] drm/amd/display: document AMDGPU pre-defined transfer functions Melissa Wen
2023-09-28 20:16   ` Harry Wentland
2023-09-29  7:35     ` Pekka Paalanen
2023-09-29 13:08       ` Harry Wentland [this message]
2023-09-25 19:49 ` [PATCH v3 08/32] drm/amd/display: add plane HDR multiplier driver-specific property Melissa Wen
2023-09-25 19:49 ` [PATCH v3 09/32] drm/amd/display: add plane 3D LUT driver-specific properties Melissa Wen
2023-09-27 18:47   ` Harry Wentland
2023-10-03 16:17     ` Melissa Wen
2023-09-25 19:49 ` [PATCH v3 10/32] drm/amd/display: add plane shaper LUT and TF " Melissa Wen
2023-09-25 19:49 ` [PATCH v3 11/32] drm/amd/display: add plane blend " Melissa Wen
2023-09-25 19:49 ` [PATCH v3 12/32] drm/amd/display: add CRTC gamma TF driver-specific property Melissa Wen
2023-09-25 19:49 ` [PATCH v3 13/32] drm/amd/display: add comments to describe DM crtc color mgmt behavior Melissa Wen
2023-09-25 19:49 ` [PATCH v3 14/32] drm/amd/display: encapsulate atomic regamma operation Melissa Wen
2023-09-25 19:49 ` [PATCH v3 15/32] drm/amd/display: add CRTC gamma TF support Melissa Wen
2023-09-25 19:49 ` [PATCH v3 16/32] drm/amd/display: set sdr_ref_white_level to 80 for out_transfer_func Melissa Wen
2023-09-25 19:49 ` [PATCH v3 17/32] drm/amd/display: mark plane as needing reset if color props change Melissa Wen
2023-09-25 19:49 ` [PATCH v3 18/32] drm/amd/display: decouple steps for mapping CRTC degamma to DC plane Melissa Wen
2023-09-25 19:49 ` [PATCH v3 19/32] drm/amd/display: add plane degamma TF and LUT support Melissa Wen
2023-09-25 19:49 ` [PATCH v3 20/32] drm/amd/display: reject atomic commit if setting both plane and CRTC degamma Melissa Wen
2023-09-25 19:49 ` [PATCH v3 21/32] drm/amd/display: add dc_fixpt_from_s3132 helper Melissa Wen
2023-09-25 19:49 ` [PATCH v3 22/32] drm/amd/display: add HDR multiplier support Melissa Wen
2023-09-25 19:49 ` [PATCH v3 23/32] drm/amd/display: add plane shaper LUT support Melissa Wen
2023-09-27 18:47   ` Harry Wentland
2023-09-25 19:49 ` [PATCH v3 24/32] drm/amd/display: add plane shaper TF support Melissa Wen
2023-09-25 19:49 ` [PATCH v3 25/32] drm/amd/display: add plane 3D LUT support Melissa Wen
2023-09-25 19:49 ` [PATCH v3 26/32] drm/amd/display: handle empty LUTs in __set_input_tf Melissa Wen
2023-09-25 19:49 ` [PATCH v3 27/32] drm/amd/display: add plane blend LUT and TF support Melissa Wen
2023-09-25 19:49 ` [PATCH v3 28/32] drm/amd/display: allow newer DC hardware to use degamma ROM for PQ/HLG Melissa Wen
2023-09-27 18:49   ` Harry Wentland
2023-09-25 19:49 ` [PATCH v3 29/32] drm/amd/display: copy 3D LUT settings from crtc state to stream_update Melissa Wen
2023-09-25 19:49 ` [PATCH v3 30/32] drm/amd/display: add plane CTM driver-specific property Melissa Wen
2023-09-25 19:49 ` [PATCH v3 31/32] drm/amd/display: add plane CTM support Melissa Wen
2023-09-27 18:52   ` Harry Wentland
2023-09-25 19:49 ` [PATCH v3 32/32] drm/amd/display: Add 3x4 CTM support for plane CTM Melissa Wen
2023-09-27 18:53   ` Harry Wentland

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