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Date:   Tue, 26 Apr 2022 11:00:15 +0200
From:   Sebastian Fricke <sebastian.fricke@collabora.com>
To:     Benjamin Gaignard <benjamin.gaignard@collabora.com>
Cc:     mchehab@kernel.org, hverkuil@xs4all.nl,
        ezequiel@vanguardiasur.com.ar, p.zabel@pengutronix.de,
        gregkh@linuxfoundation.org, mripard@kernel.org,
        paul.kocialkowski@bootlin.com, wens@csie.org,
        jernej.skrabec@gmail.com, samuel@sholland.org,
        nicolas.dufresne@collabora.com, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
        linux-staging@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev
Subject: Re: [PATCH v5 04/17] media: uapi: HEVC: Add missing fields in HEVC
 controls
Message-ID: <20220426090015.4xhl5ubkptnvqjr2@basti-XPS-13-9310>
References: <20220407152940.738159-1-benjamin.gaignard@collabora.com>
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On 26.04.2022 10:50, Benjamin Gaignard wrote:
>
>Le 26/04/2022 à 09:52, Sebastian Fricke a écrit :
>>Hey Benjamin,
>>
>>On 25.04.2022 18:16, Benjamin Gaignard wrote:
>>>
>>>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()
>>
>>Just ...
>>
>>s/reference pictures set/reference picture set/
>>
>>>     in the specification, included in the slice header (section 
>>>7.3.6.1).
>>
>>s/slice header/slice header or SPS/
>>
>>
>>>
>>>* - __u16
>>>   - ``long_term_ref_pic_set_size``
>>>   - Specifies the size, in bits, of the long-term reference 
>>>pictures set include in the slice header.
>>
>>s/reference pictures set/reference picture set/
>>
>>Looking at the documentation it looks like: s/slice header/slice 
>>header or SPS/
>>(For example in section 7.3.6.1:
>>```
>>if( long_term_ref_pics_present_flag ) {
>>  if( num_long_term_ref_pics_sps > 0 )
>>    num_long_term_sps
>>  num_long_term_pics
>>  for( i = 0; i < num_long_term_sps + num_long_term_pics; i++ ) {
>>    ...
>>```
>>)
>>
>>... and then it looks very good!
>
>I don't know the syntax to insert this kind of comment inside an array in the documentation
>so it will remain as before :-)

Ah, no I didn't mean the pseudo code, I only gave that as an *example*
why just `slice header` seems incorrect to me.
The changes I suggest for that line are only:

s/reference pictures set/reference picture set/ (grammatical error)
s/slice header/slice header or SPS/ (correct statement)

>
>Benjamin

Greetings,
Sebastian

>
>>
>>Greetings,
>>Sebastian
>>
>>>     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
>>>>>