Hello Jernej,
I'd like to post a new H264 uAPI cleanup series soon,
would you mind resending this, or otherwise do you
mind if I include this patch in the series?
See below for a tiny comment.
On Thu, 4 Jun 2020 at 15:55, Jernej Skrabec <jernej.skrabec@xxxxxxxx> wrote:
>
> 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 flags along
> index into DPB array. Flags will tell if reference is meant for top or
> bottom field.
>
> Currently the only user of these lists is Cedrus which is just compile
> fixed here. Actual usage of newly introduced flags will come in
> following commit.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@xxxxxxxx>
> ---
> .../media/v4l/ext-ctrls-codec.rst | 40 ++++++++++++++++++-
> .../staging/media/sunxi/cedrus/cedrus_h264.c | 6 +--
> include/media/h264-ctrls.h | 12 +++++-
> 3 files changed, 51 insertions(+), 7 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..6c36d298db20 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 +1926,42 @@ 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
> +
> + * - __u16
> + - ``flags``
> + - See :ref:`Picture Reference Flags <h264_reference_flags>`
> + * - __u8
> + - ``index``
> + -
> +
> +.. _h264_reference_flags:
> +
> +``Picture Reference Flags``
> +
> +.. cssclass:: longtable
> +
> +.. flat-table::
> + :header-rows: 0
> + :stub-columns: 0
> + :widths: 1 1 2
> +
> + * - ``V4L2_H264_REFERENCE_FLAG_TOP_FIELD``
> + - 0x00000001
> + -
> + * - ``V4L2_H264_REFERENCE_FLAG_BOTTOM_FIELD``
> + - 0x00000002
> + -
> +
> ``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..9b1cbc9bc38e 100644
> --- a/include/media/h264-ctrls.h
> +++ b/include/media/h264-ctrls.h
> @@ -140,6 +140,14 @@ 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
>
> +#define V4L2_H264_REFERENCE_FLAG_TOP_FIELD 0x01
> +#define V4L2_H264_REFERENCE_FLAG_BOTTOM_FIELD 0x02
> +
> +struct v4l2_h264_reference {
> + __u8 flags;
> + __u8 index;
> +};
> +
> struct v4l2_ctrl_h264_slice_params {
> /* Size in bytes, including header */
> __u32 size;
> @@ -182,8 +190,8 @@ struct v4l2_ctrl_h264_slice_params {
> * 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[32];
> + struct v4l2_h264_reference ref_pic_list1[32];
>
Could we use a macro for "32" here? Something like:
#define V4L2_H264_REF_PIC_LIST_LEN (V4L2_H264_NUM_DPB_ENTRIES * 2).
Does it make sense to add a comment as well?
I was thinking something along these lines:
"""
Pictures in the DPB can be a frame, a complementary field pair or a
single field.
Therefore, reference pictures lists need twice as much entries, so it
can reference
either field of a field pair.
"""
While it doesn't replace proper H264 specification reading,
it would add some clarity.
Thanks,
Ezequiel
