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

Hans Verkuil
2022-07-06T07:58:07Z

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
>>>