Re: [PATCH v5 04/17] media: uapi: HEVC: Add missing fields in HEVC controls

[Sebastian Fricke]

On 07.04.2022 17:29, Benjamin Gaignard wrote:
> Complete the HEVC controls with missing fields from H.265 specifications.
> Even if these fields aren't used by the current mainlined drivers
> they will be need for (at least) rkvdec driver.

s/be need/be required/
or
s/be need/be needed/

s/rkvdec/the rkvdec/

> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> ---
> .../media/v4l/ext-ctrls-codec.rst             | 19 +++++++++++++++++++
> include/media/hevc-ctrls.h                    |  6 +++++-
> 2 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 4cd7c541fc30..dbb08603217b 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -2661,6 +2661,16 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>     :stub-columns: 0
>     :widths:       1 1 2
>
> +    * - __u8
> +      - ``video_parameter_set_id``
> +      - Specifies the value of the vps_video_parameter_set_id of the active VPS
> +        as descibed in section "7.4.3.2.1 General sequence parameter set RBSP semantics"
> +        of H.265 specifications.
> +    * - __u8
> +      - ``seq_parameter_set_id``
> +      - Provides an identifier for the SPS for reference by other syntax elements
> +        as descibed in section "7.4.3.2.1 General sequence parameter set RBSP semantics"
> +        of H.265 specifications.
>     * - __u16
>       - ``pic_width_in_luma_samples``
>       -
> @@ -2800,6 +2810,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>     :stub-columns: 0
>     :widths:       1 1 2
>
> +    * - __u8
> +      - ``pic_parameter_set_id``
> +      - Identifies the PPS for reference by other syntax elements.
>     * - __u8
>       - ``num_extra_slice_header_bits``
>       -
> @@ -3026,6 +3039,12 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>     * - __u8
>       - ``ref_idx_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
>       - The list of L1 reference elements as indices in the DPB.
> +    * - __u16
> +      - ``short_term_ref_pic_set_size``
> +      - Specifies the size of short-term reference pictures set included in the SPS.

s/size of/size of the/

Section 7.4.8 depicts that the st_ref_pic_set syntax
structure can be part of the SPS or the slice header.

I think we should mention that we talk about the size of the st_ref_pic_set
syntax structure from section 7.4.8 of the specification. 

> +    * - __u16
> +      - ``long_term_ref_pic_set_size``
> +      - Specifies the size of long-term reference pictures set include in the SPS.

s/size of/size of the/

Can we make this a bit more helpful? The specification doesn't contain
a similar structure to `st_ref_pic_set` for long term pictures. So, as a
programmer this leaves me guessing:
- Which syntax structure's size are we talking about?
- Does this correlate to any of the existing sections of the
specification?
Because in the end, I feel like this documentation should be able to
help a programmer to provide the correct data for the uABI.

Greetings,
Sebastian

>     * - __u8
>       - ``padding``
>       - Applications and drivers must set this to zero.
> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> index 01ccda48d8c5..a329e086a89a 100644
> --- a/include/media/hevc-ctrls.h
> +++ b/include/media/hevc-ctrls.h
> @@ -58,6 +58,8 @@ enum v4l2_mpeg_video_hevc_start_code {
> /* The controls are not stable at the moment and will likely be reworked. */
> struct v4l2_ctrl_hevc_sps {
> 	/* ISO/IEC 23008-2, ITU-T Rec. H.265: Sequence parameter set */
> +	__u8	video_parameter_set_id;
> +	__u8	seq_parameter_set_id;
> 	__u16	pic_width_in_luma_samples;
> 	__u16	pic_height_in_luma_samples;
> 	__u8	bit_depth_luma_minus8;
> @@ -108,6 +110,7 @@ struct v4l2_ctrl_hevc_sps {
>
> struct v4l2_ctrl_hevc_pps {
> 	/* ISO/IEC 23008-2, ITU-T Rec. H.265: Picture parameter set */
> +	__u8	pic_parameter_set_id;
> 	__u8	num_extra_slice_header_bits;
> 	__u8	num_ref_idx_l0_default_active_minus1;
> 	__u8	num_ref_idx_l1_default_active_minus1;
> @@ -199,7 +202,8 @@ struct v4l2_ctrl_hevc_slice_params {
> 	__u32	slice_segment_addr;
> 	__u8	ref_idx_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
> 	__u8	ref_idx_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
> -
> +	__u16	short_term_ref_pic_set_size;
> +	__u16	long_term_ref_pic_set_size;
> 	__u8	padding;
>
> 	/* ISO/IEC 23008-2, ITU-T Rec. H.265: Weighted prediction parameter */
> --
> 2.32.0