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

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Benjamin,

On 7/5/22 18:03, Benjamin Gaignard wrote:
> 
> Le 05/07/2022 à 17:45, Ezequiel Garcia a écrit :
>> 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.
> 
> This field is here because some drivers would like know the number of
> entry point offsets without getting the entry point offsets data itself.

I agree with Ezequiel that this needs to be documented a bit better, esp. by
having a reference to the control (and vice versa, probably). That puts this
into better context.

I assume you'll post a v11?

Regards,

	Hans

> 
> Benjamin
> 
>>
>> 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
>>>