[PATCH v3 01/15] media: uapi: HEVC: Add v4l2_ctrl_hevc_ext_sps_[ls]t_rps controls
Nicolas Dufresne
nicolas.dufresne at collabora.com
Wed Dec 10 12:03:06 PST 2025
Hi,
Le mercredi 22 octobre 2025 à 12:22 -0400, Detlev Casanova a écrit :
> Some hardware (e.g.: Rockchip's rk3588 hevc decoder) need the
> long and short term reference information for HEVC decoding.
That's seems a bit short and incomplete. My understanding is that the decoder on
this hardware needs to full parse the slice headers, and cannot be passed with
the slice information. It also does not implement a a skip method similar to
Hantro.
So in short, I think the justification for this API is that these parameters are
needed to fully parse HEVC slice headers. You should perhaps say that similar
paramters ares passed in Vulkan Video API ?
>
> Add controls to provide it as the raw data form the stream.
>
> Signed-off-by: Detlev Casanova <detlev.casanova at collabora.com>
> ---
> .../media/v4l/ext-ctrls-codec-stateless.rst | 114 ++++++++++++++++++
> .../media/v4l/videodev2.h.rst.exceptions | 2 +
> .../media/v4l/vidioc-queryctrl.rst | 12 ++
> 3 files changed, 128 insertions(+)
>
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
> index 0da635691fdc..bb6772cf3cee 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
> @@ -2958,6 +2958,120 @@ This structure contains all loop filter related parameters. See sections
> - 0x00000004
> -
>
> +``V4L2_CID_STATELESS_HEVC_EXT_SPS_LT_RPS (struct)``
> + Specifies the list of Long-Term reference sets parameters from the SPS.
> + These parameters are defined according to :ref:`hevc`.
> + They are described in section 7.4.3.2.1 "General sequence parameter set
> + RBSP semantics" of the specification.
> + This control is a dynamically sized 1-dimensional array,
> + V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
Can we making a bit clearer that this is a subset of the SPS (perhaps use the
term subset). And this is user to extend another control (mention this other
control) ?
> +
> +.. c:type:: v4l2_ctrl_hevc_ext_sps_lt_rps
> +
> +.. cssclass:: longtable
> +
> +.. flat-table:: struct v4l2_ctrl_hevc_ext_sps_lt_rps
> + :header-rows: 0
> + :stub-columns: 0
> + :widths: 1 1 2
> +
> + * - __u16
> + - ``lt_ref_pic_poc_lsb_sps``
> + - Long term reference picture order count as described in section 7.4.3.2.1
> + "General sequence parameter set RBSP semantics" of the specification.
> + * - __u8
> + - ``flags``
> + - See :ref:`Extended Long-Term RPS Flags <hevc_ext_sps_lt_rps_flags>`
> +
> +.. _hevc_ext_sps_lt_rps_flags:
> +
> +``Extended SPS Long-Term RPS Flags``
> +
> +.. cssclass:: longtable
> +
> +.. flat-table::
> + :header-rows: 0
> + :stub-columns: 0
> + :widths: 1 1 2
> +
> + * - ``V4L2_HEVC_EXT_SPS_LT_RPS_FLAG_USED_LT``
> + - 0x00000001
> + - Specifies if the long-term reference picture is used 7.4.3.2.1 "General sequence parameter
> + set RBSP semantics" of the specification.
> +
> +``V4L2_CID_STATELESS_HEVC_EXT_SPS_ST_RPS (struct)``
> + Specifies the list of Short-Term reference sets parameters from the SPS.
> + These parameters are defined according to :ref:`hevc`.
> + They are described in section 7.4.8 "Short-term reference picture set
> + semantics" of the specification.
> + This control is a dynamically sized 1-dimensional array,
> + V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
Déjà vue, this is a duplicate right ?
> +
> +.. c:type:: v4l2_ctrl_hevc_ext_sps_st_rps
> +
> +.. cssclass:: longtable
> +
> +.. flat-table:: struct v4l2_ctrl_hevc_ext_sps_st_rps
> + :header-rows: 0
> + :stub-columns: 0
> + :widths: 1 1 2
> +
> + * - __u8
> + - ``delta_idx_minus1``
> + - Specifies the delta compare to the index. See details in section 7.4.8 "Short-term
> + reference picture set semantics" of the specification.
> + * - __u8
> + - ``delta_rps_sign``
> + - Sign of the delta as specified in section 7.4.8 "Short-term reference picture set
> + semantics" of the specification.
> + * - __u16
> + - ``abs_delta_rps_minus1``
> + - Absolute delta RPS as specified in section 7.4.8 "Short-term reference picture set
> + semantics" of the specification.
> + * - __u8
> + - ``num_negative_pics``
> + - Number of short-term RPS entries that have picture order count values less than the
> + picture order count value of the current picture.
> + * - __u8
> + - ``num_positive_pics``
> + - Number of short-term RPS entries that have picture order count values greater than the
> + picture order count value of the current picture.
> + * - __u32
> + - ``used_by_curr_pic``
> + - Bit i specifies if short-term RPS i is used by the current picture.
> + * - __u32
> + - ``use_delta_flag``
> + - Bit i specifies if short-term RPS i is included in the short-term RPS entries.
> + * - __u16
> + - ``delta_poc_s0_minus1[16]``
> + - Specifies the negative picture order count delta for the i-th entry in the short-term RPS.
> + See details in section 7.4.8 "Short-term reference picture set semantics" of the
> + specification.
> + * - __u16
> + - ``delta_poc_s1_minus1[16]``
> + - Specifies the positive picture order count delta for the i-th entry in the short-term RPS.
> + See details in section 7.4.8 "Short-term reference picture set semantics" of the
> + specification.
> + * - __u8
> + - ``flags``
> + - See :ref:`Extended Short-Term RPS Flags <hevc_ext_sps_st_rps_flags>`
> +
> +.. _hevc_ext_sps_st_rps_flags:
> +
> +``Extended SPS Short-Term RPS Flags``
> +
> +.. cssclass:: longtable
> +
> +.. flat-table::
> + :header-rows: 0
> + :stub-columns: 0
> + :widths: 1 1 2
> +
> + * - ``V4L2_HEVC_EXT_SPS_ST_RPS_FLAG_INTER_REF_PIC_SET_PRED``
> + - 0x00000001
> + - Specifies if the short-term RPS is predicted from another short term RPS. See details in
> + section 7.4.8 "Short-term reference picture set semantics" of the specification.
> +
> .. _v4l2-codec-stateless-av1:
>
> ``V4L2_CID_STATELESS_AV1_SEQUENCE (struct)``
> diff --git a/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions
> index 35d3456cc812..1663fdf8444c 100644
> --- a/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions
> +++ b/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions
> @@ -149,6 +149,8 @@ replace symbol V4L2_CTRL_TYPE_H264_DECODE_PARAMS :c:type:`v4l2_ctrl_type`
> replace symbol V4L2_CTRL_TYPE_HEVC_SPS :c:type:`v4l2_ctrl_type`
> replace symbol V4L2_CTRL_TYPE_HEVC_PPS :c:type:`v4l2_ctrl_type`
> replace symbol V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS :c:type:`v4l2_ctrl_type`
> +replace symbol V4L2_CTRL_TYPE_HEVC_EXT_SPS_ST_RPS :c:type:`v4l2_ctrl_type`
> +replace symbol V4L2_CTRL_TYPE_HEVC_EXT_SPS_LT_RPS :c:type:`v4l2_ctrl_type`
> replace symbol V4L2_CTRL_TYPE_AREA :c:type:`v4l2_ctrl_type`
> replace symbol V4L2_CTRL_TYPE_RECT :c:type:`v4l2_ctrl_type`
> replace symbol V4L2_CTRL_TYPE_FWHT_PARAMS :c:type:`v4l2_ctrl_type`
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
> index 3549417c7feb..128c044d2e3c 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
> @@ -523,6 +523,18 @@ See also the examples in :ref:`control`.
> - n/a
> - A struct :c:type:`v4l2_ctrl_hevc_decode_params`, containing HEVC
> decoding parameters for stateless video decoders.
> + * - ``V4L2_CTRL_TYPE_HEVC_EXT_SPS_LT_RPS``
> + - n/a
> + - n/a
> + - n/a
> + - A struct :c:type:`v4l2_ctrl_hevc_ext_sps_lt_rps`, containing HEVC
> + extended Long-Term RPS for stateless video decoders.
> + * - ``V4L2_CTRL_TYPE_HEVC_EXT_SPS_ST_RPS``
> + - n/a
> + - n/a
> + - n/a
> + - A struct :c:type:`v4l2_ctrl_hevc_ext_sps_st_rps`, containing HEVC
> + extended Short-Term RPS for stateless video decoders.
> * - ``V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR``
> - n/a
> - n/a
cheers,
Nicolas
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