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Message-ID: <511c900070050a5cac317279ee4208cdc1d8d1af.camel@collabora.com>
Subject: Re: [PATCH] media: uapi: HEVC: Add num_delta_pocs_of_ref_rps_idx
 field
From:   Nicolas Dufresne <nicolas.dufresne@collabora.com>
To:     Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        mchehab@kernel.org, hverkuil-cisco@xs4all.nl
Cc:     linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel@collabora.com
Date:   Wed, 19 Apr 2023 16:10:38 -0400
In-Reply-To: <20230418160717.743517-1-benjamin.gaignard@collabora.com>
References: <20230418160717.743517-1-benjamin.gaignard@collabora.com>
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Le mardi 18 avril 2023 =C3=A0 18:07 +0200, Benjamin Gaignard a =C3=A9crit=
=C2=A0:
> Some drivers firmwares parse by themselves slice header and need
> num_delta_pocs_of_ref_rps_idx value to parse slice header
> short_term_ref_pic_set().
> Use one of the 4 reserved bytes to store this value without
> changing the v4l2_ctrl_hevc_decode_params structure size and padding.
>=20
> This value also exist in DXVA API.
>=20
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>=20

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>

For the info, this is in preparation for MTK VCODEC HEVC driver. It makes o=
ur
API (hopefully) on par with DXVA, which has always been the goal, we simply
missed it during review.

regards,
Nicolas

> ---
>  .../userspace-api/media/v4l/ext-ctrls-codec-stateless.rst  | 7 +++++++
>  include/uapi/linux/v4l2-controls.h                         | 6 +++++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
>=20
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-statel=
ess.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.r=
st
> index 3d8411acd5b8..92ce3e126929 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
> @@ -2923,6 +2923,13 @@ This structure contains all loop filter related pa=
rameters. See sections
>        - ``poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
>        - PocLtCurr as described in section 8.3.2 "Decoding process for re=
ference
>          picture set": provides the index of the long term references in =
DPB array.
> +    * - __u8
> +      - ``num_delta_pocs_of_ref_rps_idx``
> +      - When the short_term_ref_pic_set_sps_flag in the slice header is =
equal to 0,
> +        it is the same than derived value NumDeltaPocs[RefRpsIdx]. It ca=
n be used to parse
> +        the RPS data in slice headers instead of skipping it with @short=
_term_ref_pic_set_size.
> +        When the value of short_term_ref_pic_set_sps_flag in the slice h=
eader is
> +        equal to 1, num_delta_pocs_of_ref_rps_idx shall be set to 0.
>      * - struct :c:type:`v4l2_hevc_dpb_entry`
>        - ``dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
>        - The decoded picture buffer, for meta-data about reference frames=
.
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2=
-controls.h
> index 5e80daa4ffe0..7bf59a87a1bf 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -2385,6 +2385,9 @@ struct v4l2_ctrl_hevc_slice_params {
>   * @poc_st_curr_after: provides the index of the short term after refere=
nces
>   *		       in DPB array
>   * @poc_lt_curr: provides the index of the long term references in DPB a=
rray
> + * @num_delta_pocs_of_ref_rps_idx: same as the derived value NumDeltaPoc=
s[RefRpsIdx],
> + *				   can be used to parse the RPS data in slice headers
> + *				   instead of skipping it with @short_term_ref_pic_set_size.
>   * @reserved: padding field. Should be zeroed by applications.
>   * @dpb: the decoded picture buffer, for meta-data about reference frame=
s
>   * @flags: see V4L2_HEVC_DECODE_PARAM_FLAG_{}
> @@ -2400,7 +2403,8 @@ struct v4l2_ctrl_hevc_decode_params {
>  	__u8	poc_st_curr_before[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>  	__u8	poc_st_curr_after[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>  	__u8	poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
> -	__u8	reserved[4];
> +	__u8	num_delta_pocs_of_ref_rps_idx;
> +	__u8	reserved[3];
>  	struct	v4l2_hevc_dpb_entry dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
>  	__u64	flags;
>  };