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

[Benjamin Gaignard <benjamin.gaignard@collabora.com>]

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.

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
>>

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