On Thu, 19 Dec 2024 21:33:35 -0700
Alex Hung <alex.hung@xxxxxxx> wrote:
> From: Harry Wentland <harry.wentland@xxxxxxx>
>
> The PQ function defines a mapping of code values to nits (cd/m^2).
> The max code value maps to 10,000 nits.
>
> Windows DWM's canonical composition color space (CCCS) defaults
> to composing SDR contents to 80 nits and uses a float value of
> 1.0 to represent this. For this reason AMD HW hard-codes a PQ
> function that is scaled by 125, yielding 80 nit PQ values for
> 1.0 and 10,000 nits at 125.0.
>
> This patch introduces this scaled PQ EOTF and its inverse as
> 1D curve types.
>
> Signed-off-by: Alex Hung <alex.hung@xxxxxxx>
> Signed-off-by: Harry Wentland <harry.wentland@xxxxxxx>
> ---
> drivers/gpu/drm/drm_colorop.c | 2 ++
> include/drm/drm_colorop.h | 21 ++++++++++++++++++++-
> 2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_colorop.c b/drivers/gpu/drm/drm_colorop.c
> index 7d4b29c0a0cc..f3391602a577 100644
> --- a/drivers/gpu/drm/drm_colorop.c
> +++ b/drivers/gpu/drm/drm_colorop.c
> @@ -70,6 +70,8 @@ static const struct drm_prop_enum_list drm_colorop_type_enum_list[] = {
> static const char * const colorop_curve_1d_type_names[] = {
> [DRM_COLOROP_1D_CURVE_SRGB_EOTF] = "sRGB EOTF",
> [DRM_COLOROP_1D_CURVE_SRGB_INV_EOTF] = "sRGB Inverse EOTF",
> + [DRM_COLOROP_1D_CURVE_PQ_125_EOTF] = "PQ 125 EOTF",
> + [DRM_COLOROP_1D_CURVE_PQ_125_INV_EOTF] = "PQ 125 Inverse EOTF",
> };
>
>
> diff --git a/include/drm/drm_colorop.h b/include/drm/drm_colorop.h
> index e9f5c1adc2fe..4084a7438032 100644
> --- a/include/drm/drm_colorop.h
> +++ b/include/drm/drm_colorop.h
> @@ -36,7 +36,6 @@
> * enum drm_colorop_curve_1d_type - type of 1D curve
> *
> * Describes a 1D curve to be applied by the DRM_COLOROP_1D_CURVE colorop.
> - *
> */
> enum drm_colorop_curve_1d_type {
> /**
> @@ -56,6 +55,26 @@ enum drm_colorop_curve_1d_type {
> */
> DRM_COLOROP_1D_CURVE_SRGB_INV_EOTF,
>
> + /**
> + * @DRM_COLOROP_1D_CURVE_PQ_125_EOTF:
> + *
> + * The PQ transfer function, scaled by 125.0f, so that 10,000
> + * nits correspond to 125.0f.
> + *
> + * Transfer characteristics of the PQ function as defined by
> + * SMPTE ST 2084 (2014) for 10-, 12-, 14-, and 16-bit systems
> + * and Rec. ITU-R BT.2100-2 perceptual quantization (PQ) system.
> + * Equivalent to H.273 TransferCharacteristics code point 16.
> + */
Hi,
this all good, I'd just clarify a minor detail.
H.273 code point 16 defines the normalised formula
TF: [0.0, 1.0] -> [0.0, 1.0]
so it is not equivalent to the 125-scaled version.
Maybe you meant something like this?
+ * Transfer characteristics of the PQ function as defined by
+ * SMPTE ST 2084 (2014) for 10-, 12-, 14-, and 16-bit systems
+ * and Rec. ITU-R BT.2100-2 perceptual quantization (PQ) system,
+ * represented by H.273 TransferCharacteristics code point 16.
Thanks,
pq
> + DRM_COLOROP_1D_CURVE_PQ_125_EOTF,
> +
> + /**
> + * @DRM_COLOROP_1D_CURVE_PQ_125_INV_EOTF:
> + *
> + * The inverse of DRM_COLOROP_1D_CURVE_PQ_125_EOTF.
> + */
> + DRM_COLOROP_1D_CURVE_PQ_125_INV_EOTF,
> +
> /**
> * @DRM_COLOROP_1D_CURVE_COUNT:
> *
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