Re: [PATCH 06/10] media: uapi: h264: Cleanup DPB entry interface

From: Jernej Åkrabec
Date: Wed Jul 22 2020 - 12:09:31 EST

Hi!

Dne sreda, 15. julij 2020 ob 22:22:29 CEST je Ezequiel Garcia napisal(a):
> As discussed recently, the current interface for the
> Decoded Picture Buffer is not enough to properly
> support field coding.
>
> This commit introduces enough semantics to support
> frame and field coding, and to signal how DPB entries
> are "used for reference".
>
> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx>
> ---
> .../media/v4l/ext-ctrls-codec.rst | 46 ++++++++++++-------
> drivers/media/v4l2-core/v4l2-h264.c | 4 +-
> drivers/staging/media/rkvdec/rkvdec-h264.c | 8 ++--
> include/media/h264-ctrls.h | 8 +++-
> 4 files changed, 42 insertions(+), 24 deletions(-)
>
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst index
> dd8e5a2e8986..46d4c8c6ad47 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -2058,10 +2058,35 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
> * - __s32
> - ``bottom_field_order_cnt``
> -
> + * - enum :c:type:`v4l2_h264_dpb_reference`
> + - ``reference``
> + - Specifies how the DPB entry is referenced.
> * - __u32
> - ``flags``
> - See :ref:`DPB Entry Flags <h264_dpb_flags>`
>
> +.. 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.
> +
> .. _h264_dpb_flags:
>
> ``DPB Entries Flags``
> @@ -2075,29 +2100,16 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
>
> * - ``V4L2_H264_DPB_ENTRY_FLAG_VALID``
> - 0x00000001
> - - The DPB entry is valid and should be considered
> + - The DPB entry is valid (non-empty) and should be considered.
> * - ``V4L2_H264_DPB_ENTRY_FLAG_ACTIVE``

I'm still not sure that we actually need both flags. Technically, if entry is
not used for reference then doesn't need to be present. Am I missing
something?

Best regards,
Jernej

> - 0x00000002
> - - The DPB entry is currently being used as a reference frame
> + - The DPB entry is used for reference.
> * - ``V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM``
> - 0x00000004
> - - The DPB entry is a long term reference frame
> + - The DPB entry is used for long-term reference.
> * - ``V4L2_H264_DPB_ENTRY_FLAG_FIELD``
> - 0x00000008
> - - The DPB entry is a field reference, which means only one of the
> field - will be used when decoding the new frame/field. When not set
> the DPB - entry is a frame reference (both fields will be used).
> Note that this - flag does not say anything about the number of
> fields contained in the - reference frame, it just describes the one
> used to decode the new - field/frame
> - * - ``V4L2_H264_DPB_ENTRY_FLAG_BOTTOM_FIELD``
> - - 0x00000010
> - - The DPB entry is a bottom field reference (only the bottom field of
> the - reference frame is needed to decode the new frame/field). Only
> valid if - V4L2_H264_DPB_ENTRY_FLAG_FIELD is set. When
> - V4L2_H264_DPB_ENTRY_FLAG_FIELD is set but
> - V4L2_H264_DPB_ENTRY_FLAG_BOTTOM_FIELD is not, that means the
> - DPB entry is a top field reference
> + - The DPB entry is a single field or a complementary field pair.
>
> ``V4L2_CID_MPEG_VIDEO_H264_DECODE_MODE (enum)``
> Specifies the decoding mode to use. Currently exposes slice-based and
> diff --git a/drivers/media/v4l2-core/v4l2-h264.c
> b/drivers/media/v4l2-core/v4l2-h264.c index edf6225f0522..306a51683606
> 100644
> --- a/drivers/media/v4l2-core/v4l2-h264.c
> +++ b/drivers/media/v4l2-core/v4l2-h264.c
> @@ -66,10 +66,10 @@ v4l2_h264_init_reflist_builder(struct
> v4l2_h264_reflist_builder *b, else
> b->refs[i].frame_num = dpb[i].frame_num;
>
> - if (!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_FIELD))
> + if (dpb[i].reference & V4L2_H264_DPB_FRAME_REF)
> pic_order_count =
min(dpb[i].top_field_order_cnt,
>
dpb[i].bottom_field_order_cnt);
> - else if (dpb[i].flags &
V4L2_H264_DPB_ENTRY_FLAG_BOTTOM_FIELD)
> + else if (dpb[i].reference & V4L2_H264_DPB_BOTTOM_REF)
> pic_order_count =
dpb[i].bottom_field_order_cnt;
> else
> pic_order_count = dpb[i].top_field_order_cnt;
> diff --git a/drivers/staging/media/rkvdec/rkvdec-h264.c
> b/drivers/staging/media/rkvdec/rkvdec-h264.c index
> 7b66e2743a4f..57539c630422 100644
> --- a/drivers/staging/media/rkvdec/rkvdec-h264.c
> +++ b/drivers/staging/media/rkvdec/rkvdec-h264.c
> @@ -953,11 +953,11 @@ static void config_registers(struct rkvdec_ctx *ctx,
> RKVDEC_COLMV_USED_FLAG_REF;
>
> if (!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_FIELD))
> - refer_addr |= RKVDEC_TOPFIELD_USED_REF |
> - RKVDEC_BOTFIELD_USED_REF;
> - else if (dpb[i].flags &
V4L2_H264_DPB_ENTRY_FLAG_BOTTOM_FIELD)
> + refer_addr |= RKVDEC_FIELD_REF;
> +
> + if (dpb[i].reference & V4L2_H264_DPB_TOP_REF)
> refer_addr |= RKVDEC_BOTFIELD_USED_REF;
> - else
> + else if (dpb[i].reference & V4L2_H264_DPB_BOTTOM_REF)
> refer_addr |= RKVDEC_TOPFIELD_USED_REF;
>
> writel_relaxed(dpb[i].top_field_order_cnt,
> diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
> index 620ee8863d74..52f3976b986c 100644
> --- a/include/media/h264-ctrls.h
> +++ b/include/media/h264-ctrls.h
> @@ -202,7 +202,12 @@ struct v4l2_ctrl_h264_slice_params {
> #define V4L2_H264_DPB_ENTRY_FLAG_ACTIVE 0x02
> #define V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM 0x04
> #define V4L2_H264_DPB_ENTRY_FLAG_FIELD 0x08
> -#define V4L2_H264_DPB_ENTRY_FLAG_BOTTOM_FIELD 0x10
> +
> +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_dpb_entry {
> __u64 reference_ts;
> @@ -211,6 +216,7 @@ struct v4l2_h264_dpb_entry {
> /* Note that field is indicated by v4l2_buffer.field */
> __s32 top_field_order_cnt;
> __s32 bottom_field_order_cnt;
> + enum v4l2_h264_dpb_reference reference;
> __u32 flags; /* V4L2_H264_DPB_ENTRY_FLAG_* */
> };