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    Subject[PATCH v6 03/11] media: uapi: h264: Add the concept of decoding mode
    Date
    From: Boris Brezillon <boris.brezillon@collabora.com>

    Some stateless decoders don't support per-slice decoding granularity
    (or at least not in a way that would make them efficient or easy to use).

    Expose a menu to control the supported decoding modes. Drivers are
    allowed to support only one decoding but they can support both too.

    Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
    Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
    Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
    ---
    Changes in v6:
    * Fix spec, specifiying the decode-mode pixelformat modifier
    needs to be set once, as suggested by Hans.
    * Rename, as suggested by Paul.
    Changes in v5:
    * Improve specification as suggested by Hans.
    Changes in v4:
    * Typos/rewording fixes
    Changes in v3:
    * s/per-{slice,frame} decoding/{slice,frame}-based decoding/
    * Add Paul's R-b
    Changes in v2:
    * Allow decoding multiple slices in per-slice decoding mode
    * Minor doc improvement/fixes
    ---
    .../media/uapi/v4l/ext-ctrls-codec.rst | 47 ++++++++++++++++++-
    .../media/uapi/v4l/pixfmt-compressed.rst | 6 ++-
    drivers/media/v4l2-core/v4l2-ctrls.c | 9 ++++
    include/media/h264-ctrls.h | 10 ++++
    4 files changed, 69 insertions(+), 3 deletions(-)

    diff --git a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
    index c5f39dd50043..623b34f61b32 100644
    --- a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
    +++ b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
    @@ -1747,6 +1747,11 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
    * - __u32
    - ``size``
    -
    + * - __u32
    + - ``start_byte_offset``
    + Offset (in bytes) from the beginning of the OUTPUT buffer to the start
    + of the slice. If the slice starts with a start code, then this is the
    + offset to such start code.
    * - __u32
    - ``header_bit_size``
    -
    @@ -1930,7 +1935,10 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
    -
    * - __u16
    - ``num_slices``
    - - Number of slices needed to decode the current frame
    + - Number of slices needed to decode the current frame/field. When
    + operating in slice-based decoding mode (see
    + :c:type:`v4l2_mpeg_video_h264_decode_mode`), this field
    + should always be set to one.
    * - __u16
    - ``nal_ref_idc``
    - NAL reference ID value coming from the NAL Unit header
    @@ -2021,6 +2029,43 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
    - 0x00000004
    - The DPB entry is a long term reference frame

    +``V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE (enum)``
    + Specifies the decoding mode to use. Currently exposes slice-based and
    + frame-based decoding but new modes might be added later on.
    + This control is used as a modifier for V4L2_PIX_FMT_H264_SLICE
    + pixel format. Applications that support V4L2_PIX_FMT_H264_SLICE
    + are required to set this control in order to specify the decoding mode
    + that is expected for the buffer.
    + Drivers may expose a single or multiple decoding modes, depending
    + on what they can support.
    +
    + .. note::
    +
    + This menu control is not yet part of the public kernel API and
    + it is expected to change.
    +
    +.. c:type:: v4l2_mpeg_video_h264_decode_mode
    +
    +.. cssclass:: longtable
    +
    +.. flat-table::
    + :header-rows: 0
    + :stub-columns: 0
    + :widths: 1 1 2
    +
    + * - ``V4L2_MPEG_VIDEO_H264_DECODE_MODE_SLICE_BASED``
    + - 0
    + - Decoding is done at the slice granularity.
    + v4l2_ctrl_h264_decode_params->num_slices should be set to 1.
    + The OUTPUT buffer must contain a single slice.
    + * - ``V4L2_MPEG_VIDEO_H264_DECODE_MODE_FRAME_BASED``
    + - 1
    + - Decoding is done at the frame granularity.
    + v4l2_ctrl_h264_decode_params->num_slices should be set to the number of
    + slices forming a frame.
    + The OUTPUT buffer must contain all slices needed to decode the
    + frame. The OUTPUT buffer must also contain both fields.
    +
    .. _v4l2-mpeg-mpeg2:

    ``V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS (struct)``
    diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
    index 9b65473a2288..d666eb51741a 100644
    --- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
    +++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
    @@ -60,8 +60,10 @@ Compressed Formats
    extracted from the H264 bitstream. This format is adapted for
    stateless video decoders that implement an H264 pipeline
    (using the :ref:`mem2mem` and :ref:`media-request-api`).
    - Metadata associated with the frame to decode are required to
    - be passed through the ``V4L2_CID_MPEG_VIDEO_H264_SPS``,
    + This pixelformat has a modifier that must be set at least once
    + through the ``V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE`` control.
    + In addition, metadata associated with the frame to decode are
    + required to be passed through the ``V4L2_CID_MPEG_VIDEO_H264_SPS``,
    ``V4L2_CID_MPEG_VIDEO_H264_PPS``,
    ``V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX``,
    ``V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS`` and
    diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
    index cd1ae016706f..2c67f9fc4d5b 100644
    --- a/drivers/media/v4l2-core/v4l2-ctrls.c
    +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
    @@ -402,6 +402,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
    "Explicit",
    NULL,
    };
    + static const char * const h264_decode_mode[] = {
    + "Slice-Based",
    + "Frame-Based",
    + NULL,
    + };
    static const char * const mpeg_mpeg2_level[] = {
    "Low",
    "Main",
    @@ -633,6 +638,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
    return h264_fp_arrangement_type;
    case V4L2_CID_MPEG_VIDEO_H264_FMO_MAP_TYPE:
    return h264_fmo_map_type;
    + case V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE:
    + return h264_decode_mode;
    case V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL:
    return mpeg_mpeg2_level;
    case V4L2_CID_MPEG_VIDEO_MPEG2_PROFILE:
    @@ -852,6 +859,7 @@ const char *v4l2_ctrl_get_name(u32 id)
    case V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX: return "H264 Scaling Matrix";
    case V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS: return "H264 Slice Parameters";
    case V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS: return "H264 Decode Parameters";
    + case V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE: return "H264 Decode Mode";
    case V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL: return "MPEG2 Level";
    case V4L2_CID_MPEG_VIDEO_MPEG2_PROFILE: return "MPEG2 Profile";
    case V4L2_CID_MPEG_VIDEO_MPEG4_I_FRAME_QP: return "MPEG4 I-Frame QP Value";
    @@ -1220,6 +1228,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
    case V4L2_CID_MPEG_VIDEO_H264_VUI_SAR_IDC:
    case V4L2_CID_MPEG_VIDEO_H264_SEI_FP_ARRANGEMENT_TYPE:
    case V4L2_CID_MPEG_VIDEO_H264_FMO_MAP_TYPE:
    + case V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE:
    case V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL:
    case V4L2_CID_MPEG_VIDEO_MPEG2_PROFILE:
    case V4L2_CID_MPEG_VIDEO_MPEG4_LEVEL:
    diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
    index 6160a69c0143..928c48c57282 100644
    --- a/include/media/h264-ctrls.h
    +++ b/include/media/h264-ctrls.h
    @@ -26,6 +26,7 @@
    #define V4L2_CID_MPEG_VIDEO_H264_SCALING_MATRIX (V4L2_CID_MPEG_BASE+1002)
    #define V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS (V4L2_CID_MPEG_BASE+1003)
    #define V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS (V4L2_CID_MPEG_BASE+1004)
    +#define V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE (V4L2_CID_MPEG_BASE+1005)

    /* enum v4l2_ctrl_type type values */
    #define V4L2_CTRL_TYPE_H264_SPS 0x0110
    @@ -34,6 +35,11 @@
    #define V4L2_CTRL_TYPE_H264_SLICE_PARAMS 0x0113
    #define V4L2_CTRL_TYPE_H264_DECODE_PARAMS 0x0114

    +enum v4l2_mpeg_video_h264_decode_mode {
    + V4L2_MPEG_VIDEO_H264_DECODE_MODE_SLICE_BASED,
    + V4L2_MPEG_VIDEO_H264_DECODE_MODE_FRAME_BASED,
    +};
    +
    #define V4L2_H264_SPS_CONSTRAINT_SET0_FLAG 0x01
    #define V4L2_H264_SPS_CONSTRAINT_SET1_FLAG 0x02
    #define V4L2_H264_SPS_CONSTRAINT_SET2_FLAG 0x04
    @@ -125,6 +131,10 @@ struct v4l2_h264_pred_weight_table {
    struct v4l2_ctrl_h264_slice_params {
    /* Size in bytes, including header */
    __u32 size;
    +
    + /* Offset in bytes to the start of slice in the OUTPUT buffer. */
    + __u32 start_byte_offset;
    +
    /* Offset in bits to slice_data() from the beginning of this slice. */
    __u32 header_bit_size;

    --
    2.22.0
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