Re: [PATCH v10 11/17] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS control

[Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>]

Hi guys,

On Tue, Jul 05, 2022 at 10:54:14AM +0200, Benjamin Gaignard wrote:
> The number of 'entry point offset' can be very variable.
> Instead of using a large static array define a v4l2 dynamic array
> of U32 (V4L2_CTRL_TYPE_U32).
> The number of entry point offsets is reported by the elems field
> and in struct v4l2_ctrl_hevc_slice_params.num_entry_point_offsets
> field.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> Acked-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> Tested-by: Jernej Skrabec <jernej.skrabec@gmail.com>
> ---
>  .../userspace-api/media/v4l/ext-ctrls-codec.rst       | 11 +++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls-defs.c             |  5 +++++
>  include/media/hevc-ctrls.h                            |  5 ++++-
>  3 files changed, 20 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 db0df7d9f27c..8df8d7fdfe70 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -3010,6 +3010,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>      * - __u32
>        - ``data_bit_offset``
>        - Offset (in bits) to the video data in the current slice data.
> +    * - __u32
> +      - ``num_entry_point_offsets``
> +      - Specifies the number of entry point offset syntax elements in the slice header.

This looks underdocumented. Somewhere in the docs it should be mentioned
that the field 'num_entry_point_offsets' is linked to the control
V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS.

Thanks,
Ezequiel

>      * - __u8
>        - ``nal_unit_type``
>        - Specifies the coding type of the slice (B, P or I).
> @@ -3150,6 +3153,14 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>  
>      \normalsize
>  
> +``V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (integer)``
> +    Specifies entry point offsets in bytes.
> +    This control is a dynamically sized array. The number of entry point
> +    offsets is reported by the ``elems`` field.
> +    This bitstream parameter is defined according to :ref:`hevc`.
> +    They are described in section 7.4.7.1 "General slice segment header
> +    semantics" of the specification.
> +
>  ``V4L2_CID_STATELESS_HEVC_SCALING_MATRIX (struct)``
>      Specifies the HEVC scaling matrix parameters used for the scaling process
>      for transform coefficients.
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> index d594efbcbb93..e22921e7ea61 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -1188,6 +1188,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:		return "HEVC Decode Parameters";
>  	case V4L2_CID_STATELESS_HEVC_DECODE_MODE:		return "HEVC Decode Mode";
>  	case V4L2_CID_STATELESS_HEVC_START_CODE:		return "HEVC Start Code";
> +	case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:	return "HEVC Entry Point Offsets";
>  
>  	/* Colorimetry controls */
>  	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
> @@ -1518,6 +1519,10 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>  	case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:
>  		*type = V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS;
>  		break;
> +	case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:
> +		*type = V4L2_CTRL_TYPE_U32;
> +		*flags |= V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
> +		break;
>  	case V4L2_CID_STATELESS_VP9_COMPRESSED_HDR:
>  		*type = V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR;
>  		break;
> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> index a372c184689e..3a6601a46ced 100644
> --- a/include/media/hevc-ctrls.h
> +++ b/include/media/hevc-ctrls.h
> @@ -20,6 +20,7 @@
>  #define V4L2_CID_STATELESS_HEVC_DECODE_PARAMS	(V4L2_CID_CODEC_BASE + 1012)
>  #define V4L2_CID_STATELESS_HEVC_DECODE_MODE	(V4L2_CID_CODEC_BASE + 1015)
>  #define V4L2_CID_STATELESS_HEVC_START_CODE	(V4L2_CID_CODEC_BASE + 1016)
> +#define V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (V4L2_CID_CODEC_BASE + 1017)
>  
>  /* enum v4l2_ctrl_type type values */
>  #define V4L2_CTRL_TYPE_HEVC_SPS 0x0120
> @@ -316,6 +317,8 @@ struct v4l2_hevc_pred_weight_table {
>   *
>   * @bit_size: size (in bits) of the current slice data
>   * @data_bit_offset: offset (in bits) to the video data in the current slice data
> + * @num_entry_point_offsets: specifies the number of entry point offset syntax
> + *			     elements in the slice header.
>   * @nal_unit_type: specifies the coding type of the slice (B, P or I)
>   * @nuh_temporal_id_plus1: minus 1 specifies a temporal identifier for the NAL unit
>   * @slice_type: see V4L2_HEVC_SLICE_TYPE_{}
> @@ -358,7 +361,7 @@ struct v4l2_hevc_pred_weight_table {
>  struct v4l2_ctrl_hevc_slice_params {
>  	__u32	bit_size;
>  	__u32	data_bit_offset;
> -
> +	__u32	num_entry_point_offsets;
>  	/* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
>  	__u8	nal_unit_type;
>  	__u8	nuh_temporal_id_plus1;
> -- 
> 2.32.0
>