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

Benjamin Gaignard
2022-07-06T20:29:17Z

Le 06/07/2022 à 20:49, Jernej Škrabec a écrit :
> Dne sreda, 06. julij 2022 ob 20:39:41 CEST je Ezequiel Garcia napisal(a):
>> Hi Jernej,
>>
>> On Tue, Jul 5, 2022 at 1:11 PM Jernej Škrabec <jernej.skrabec@gmail.com>
> wrote:
>>> Dne torek, 05. julij 2022 ob 18:03:28 CEST je Benjamin Gaignard
> napisal(a):
>>>> 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.
>>> Yeah, this field must be set even when entry points offset control isn't
>>> used. Additionally, if entry point offsets control is needed and if
>>> submitting multiple slices at once, length of entry point offsets array
>>> must be sum of num_entry_point_offsets of all slices in that job. Not
>>> sure where to put this explanation.
>> This confused me a bit: so you mean that this field (called
>> num_entry_point_offsets)
>> must be the sum of "num_entry_point_offsets" syntax elements for
>> slices in the request?
> No, it's the other way around. num_entry_point_offsets field has same meaning as
> in syntax. It's per slice property. I said that if there is control with all
> entry point offsets, it has to have number of elements, which is sum of all
> num_entry_point_offsets fields in slice array.
>
> Example (totaly made up):
>
> Frame has 4 slices, each with 16 entry points.
> App sends only 2 slices per job. Both num_entry_point_offsets fields in slice
> control will have value 16, but entry point offsets array control will have 32
> elements (16 entry points offsets from first and 16 entry point offsets from
> second slice).

Jernej I have used your previous answer to document this field in v11.

Regards,
Benjamin

>
> Best regards,
> Jernej
>
>> If this is the case, then perhaps it will be a mistake to name our V4L2
>> field exactly like the syntax element, since it this sum meaning.
>> Otherwise, developers would tend to get confused by it.
>>
>> What do you think?
>>
>> Thanks,
>> Ezequiel
>>
>>> Best regards,
>>> Jernej
>>>
>>>> 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