Re: [PATCH v5 04/17] media: uapi: HEVC: Add missing fields in HEVC controls

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

Le 25/04/2022 à 15:54, Sebastian Fricke a écrit :
> On 07.04.2022 17:29, Benjamin Gaignard wrote:
>> Complete the HEVC controls with missing fields from H.265 
>> specifications.
>> Even if these fields aren't used by the current mainlined drivers
>> they will be need for (at least) rkvdec driver.
>
> s/be need/be required/
> or
> s/be need/be needed/
>
> s/rkvdec/the rkvdec/
>
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> ---
>> .../media/v4l/ext-ctrls-codec.rst             | 19 +++++++++++++++++++
>> include/media/hevc-ctrls.h                    |  6 +++++-
>> 2 files changed, 24 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 4cd7c541fc30..dbb08603217b 100644
>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> @@ -2661,6 +2661,16 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>>     :stub-columns: 0
>>     :widths:       1 1 2
>>
>> +    * - __u8
>> +      - ``video_parameter_set_id``
>> +      - Specifies the value of the vps_video_parameter_set_id of the 
>> active VPS
>> +        as descibed in section "7.4.3.2.1 General sequence parameter 
>> set RBSP semantics"
>> +        of H.265 specifications.
>> +    * - __u8
>> +      - ``seq_parameter_set_id``
>> +      - Provides an identifier for the SPS for reference by other 
>> syntax elements
>> +        as descibed in section "7.4.3.2.1 General sequence parameter 
>> set RBSP semantics"
>> +        of H.265 specifications.
>>     * - __u16
>>       - ``pic_width_in_luma_samples``
>>       -
>> @@ -2800,6 +2810,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>>     :stub-columns: 0
>>     :widths:       1 1 2
>>
>> +    * - __u8
>> +      - ``pic_parameter_set_id``
>> +      - Identifies the PPS for reference by other syntax elements.
>>     * - __u8
>>       - ``num_extra_slice_header_bits``
>>       -
>> @@ -3026,6 +3039,12 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>>     * - __u8
>>       - ``ref_idx_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
>>       - The list of L1 reference elements as indices in the DPB.
>> +    * - __u16
>> +      - ``short_term_ref_pic_set_size``
>> +      - Specifies the size of short-term reference pictures set 
>> included in the SPS.
>
> s/size of/size of the/
>
> Section 7.4.8 depicts that the st_ref_pic_set syntax
> structure can be part of the SPS or the slice header.
>
> I think we should mention that we talk about the size of the 
> st_ref_pic_set
> syntax structure from section 7.4.8 of the specification.
>> +    * - __u16
>> +      - ``long_term_ref_pic_set_size``
>> +      - Specifies the size of long-term reference pictures set 
>> include in the SPS.
>
> s/size of/size of the/
>
> Can we make this a bit more helpful? The specification doesn't contain
> a similar structure to `st_ref_pic_set` for long term pictures. So, as a
> programmer this leaves me guessing:
> - Which syntax structure's size are we talking about?
> - Does this correlate to any of the existing sections of the
> specification?
> Because in the end, I feel like this documentation should be able to
> help a programmer to provide the correct data for the uABI.

I will reword it like that:

   * - __u16
     - ``short_term_ref_pic_set_size``
     - Specifies the size, in bits, of the short-term reference pictures set, described as st_ref_pic_set()
       in the specification, included in the slice header (section 7.3.6.1).

  * - __u16
    - ``long_term_ref_pic_set_size``
    - Specifies the size, in bits, of the long-term reference pictures set include in the slice header.
      It is the number of bits in the conditional block if( long_term_ref_pics_present_flag ) {...}
      in section 7.3.6.1 of the specification.

Benjamin


>
> Greetings,
> Sebastian
>
>>     * - __u8
>>       - ``padding``
>>       - Applications and drivers must set this to zero.
>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
>> index 01ccda48d8c5..a329e086a89a 100644
>> --- a/include/media/hevc-ctrls.h
>> +++ b/include/media/hevc-ctrls.h
>> @@ -58,6 +58,8 @@ enum v4l2_mpeg_video_hevc_start_code {
>> /* The controls are not stable at the moment and will likely be 
>> reworked. */
>> struct v4l2_ctrl_hevc_sps {
>>     /* ISO/IEC 23008-2, ITU-T Rec. H.265: Sequence parameter set */
>> +    __u8    video_parameter_set_id;
>> +    __u8    seq_parameter_set_id;
>>     __u16    pic_width_in_luma_samples;
>>     __u16    pic_height_in_luma_samples;
>>     __u8    bit_depth_luma_minus8;
>> @@ -108,6 +110,7 @@ struct v4l2_ctrl_hevc_sps {
>>
>> struct v4l2_ctrl_hevc_pps {
>>     /* ISO/IEC 23008-2, ITU-T Rec. H.265: Picture parameter set */
>> +    __u8    pic_parameter_set_id;
>>     __u8    num_extra_slice_header_bits;
>>     __u8    num_ref_idx_l0_default_active_minus1;
>>     __u8    num_ref_idx_l1_default_active_minus1;
>> @@ -199,7 +202,8 @@ struct v4l2_ctrl_hevc_slice_params {
>>     __u32    slice_segment_addr;
>>     __u8    ref_idx_l0[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>>     __u8    ref_idx_l1[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>> -
>> +    __u16    short_term_ref_pic_set_size;
>> +    __u16    long_term_ref_pic_set_size;
>>     __u8    padding;
>>
>>     /* ISO/IEC 23008-2, ITU-T Rec. H.265: Weighted prediction 
>> parameter */
>> -- 
>> 2.32.0
>>