Re: [PATCH v2 01/14] media: uapi: h264: Update reference lists

[Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>]

On Thu, 6 Aug 2020 at 14:38, Ezequiel Garcia <ezequiel@collabora.com> wrote:
>
> From: Jernej Skrabec <jernej.skrabec@siol.net>
>
> When dealing with with interlaced frames, reference lists must tell if
> each particular reference is meant for top or bottom field. This info
> is currently not provided at all in the H264 related controls.
>
> Make reference lists hold a structure which will also hold an
> enumerator type along index into DPB array. The enumerator must
> be used to specify if reference is for top or bottom field.
>
> Currently the only user of these lists is Cedrus which is just compile
> fixed here. Actual usage of will come in a following commit.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
> v2:
> * As pointed out by Jonas, enum v4l2_h264_dpb_reference here.
> ---
>  .../media/v4l/ext-ctrls-codec.rst             | 44 ++++++++++++++++++-
>  .../staging/media/sunxi/cedrus/cedrus_h264.c  |  6 +--
>  include/media/h264-ctrls.h                    | 23 +++++++---
>  3 files changed, 62 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index d0d506a444b1..f2b2a381369f 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -1843,10 +1843,10 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
>      * - __u32
>        - ``slice_group_change_cycle``
>        -
> -    * - __u8
> +    * - struct :c:type:`v4l2_h264_reference`
>        - ``ref_pic_list0[32]``
>        - Reference picture list after applying the per-slice modifications
> -    * - __u8
> +    * - struct :c:type:`v4l2_h264_reference`
>        - ``ref_pic_list1[32]``
>        - Reference picture list after applying the per-slice modifications
>      * - __u32
> @@ -1926,6 +1926,46 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
>        - ``chroma_offset[32][2]``
>        -
>
> +``Picture Reference``
> +
> +.. c:type:: v4l2_h264_reference
> +
> +.. cssclass:: longtable
> +
> +.. flat-table:: struct v4l2_h264_reference
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths:       1 1 2
> +
> +    * - enum :c:type:`v4l2_h264_dpb_reference`
> +      - ``reference``
> +      - Specifies how the DPB entry is referenced.

Ah, a small overlook on my side. Given this struct
is used for DPB entries and slice references,
we should name this using something more generic,
and not mention DPB to avoid confusions.

Perhaps "struct v4l2_h264_field_reference".

Thanks!
Ezequiel


> +    * - __u8
> +      - ``index``
> +      - Index into the :c:type:`v4l2_ctrl_h264_decode_params`.dpb array.
> +
> +.. c:type:: v4l2_h264_dpb_reference
> +
> +.. cssclass:: longtable
> +
> +.. flat-table::
> +    :header-rows:  0
> +    :stub-columns: 0
> +    :widths:       1 1 2
> +
> +    * - ``V4L2_H264_DPB_TOP_REF``
> +      - 0x1
> +      - The top field in field pair is used for
> +        short-term reference.
> +    * - ``V4L2_H264_DPB_BOTTOM_REF``
> +      - 0x2
> +     - The bottom field in field pair is used for
> +        short-term reference.
> +    * - ``V4L2_H264_DPB_FRAME_REF``
> +      - 0x3
> +      - The frame (or the top/bottom fields, if it's a field pair)
> +        is used for short-term reference.
> +
>  ``V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS (struct)``
>      Specifies the decode parameters (as extracted from the bitstream)
>      for the associated H264 slice data. This includes the necessary
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> index 54ee2aa423e2..cce527bbdf86 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> @@ -166,8 +166,8 @@ static void cedrus_write_frame_list(struct cedrus_ctx *ctx,
>
>  static void _cedrus_write_ref_list(struct cedrus_ctx *ctx,
>                                    struct cedrus_run *run,
> -                                  const u8 *ref_list, u8 num_ref,
> -                                  enum cedrus_h264_sram_off sram)
> +                                  const struct v4l2_h264_reference *ref_list,
> +                                  u8 num_ref, enum cedrus_h264_sram_off sram)
>  {
>         const struct v4l2_ctrl_h264_decode_params *decode = run->h264.decode_params;
>         struct vb2_queue *cap_q;
> @@ -188,7 +188,7 @@ static void _cedrus_write_ref_list(struct cedrus_ctx *ctx,
>                 int buf_idx;
>                 u8 dpb_idx;
>
> -               dpb_idx = ref_list[i];
> +               dpb_idx = ref_list[i].index;
>                 dpb = &decode->dpb[dpb_idx];
>
>                 if (!(dpb->flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE))
> diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
> index 080fd1293c42..4c0bb7f5fb05 100644
> --- a/include/media/h264-ctrls.h
> +++ b/include/media/h264-ctrls.h
> @@ -19,6 +19,8 @@
>   */
>  #define V4L2_H264_NUM_DPB_ENTRIES 16
>
> +#define V4L2_H264_REF_LIST_LEN (2 * V4L2_H264_NUM_DPB_ENTRIES)
> +
>  /* Our pixel format isn't stable at the moment */
>  #define V4L2_PIX_FMT_H264_SLICE v4l2_fourcc('S', '2', '6', '4') /* H264 parsed slices */
>
> @@ -140,6 +142,19 @@ struct v4l2_h264_pred_weight_table {
>  #define V4L2_H264_SLICE_FLAG_DIRECT_SPATIAL_MV_PRED    0x04
>  #define V4L2_H264_SLICE_FLAG_SP_FOR_SWITCH             0x08
>
> +enum v4l2_h264_dpb_reference {
> +       V4L2_H264_DPB_TOP_REF = 0x1,
> +       V4L2_H264_DPB_BOTTOM_REF = 0x2,
> +       V4L2_H264_DPB_FRAME_REF = 0x3,
> +};
> +
> +struct v4l2_h264_reference {
> +       enum v4l2_h264_dpb_reference fields;
> +
> +       /* Index into v4l2_ctrl_h264_decode_params.dpb[] */
> +       __u8 index;
> +};
> +
>  struct v4l2_ctrl_h264_slice_params {
>         /* Size in bytes, including header */
>         __u32 size;
> @@ -178,12 +193,8 @@ struct v4l2_ctrl_h264_slice_params {
>         __u8 num_ref_idx_l1_active_minus1;
>         __u32 slice_group_change_cycle;
>
> -       /*
> -        * Entries on each list are indices into
> -        * v4l2_ctrl_h264_decode_params.dpb[].
> -        */
> -       __u8 ref_pic_list0[32];
> -       __u8 ref_pic_list1[32];
> +       struct v4l2_h264_reference ref_pic_list0[V4L2_H264_REF_LIST_LEN];
> +       struct v4l2_h264_reference ref_pic_list1[V4L2_H264_REF_LIST_LEN];
>
>         __u32 flags;
>  };
> --
> 2.27.0
>