Re: Re: [PATCH v10 11/17] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS control

Ezequiel Garcia
2022-07-06T18:43:18Z

Hi Jernej,

On Tue, Jul 5, 2022 at 1:11 PM Jernej Škrabec <jernej.skrabec@gmail.com> wrote:
>
> Dne torek, 05. julij 2022 ob 18:03:28 CEST je Benjamin Gaignard napisal(a):
> > Le 05/07/2022 à 17:45, Ezequiel Garcia a écrit :
> > > Hi guys,
> > >
> > > On Tue, Jul 05, 2022 at 10:54:14AM +0200, Benjamin Gaignard wrote:
> > >> The number of 'entry point offset' can be very variable.
> > >> Instead of using a large static array define a v4l2 dynamic array
> > >> of U32 (V4L2_CTRL_TYPE_U32).
> > >> The number of entry point offsets is reported by the elems field
> > >> and in struct v4l2_ctrl_hevc_slice_params.num_entry_point_offsets
> > >> field.
> > >>
> > >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> > >> Acked-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> > >> Tested-by: Jernej Skrabec <jernej.skrabec@gmail.com>
> > >> ---
> > >>
> > >> .../userspace-api/media/v4l/ext-ctrls-codec.rst | 11 +++++++++++
> > >> drivers/media/v4l2-core/v4l2-ctrls-defs.c | 5 +++++
> > >> include/media/hevc-ctrls.h | 5 ++++-
> > >> 3 files changed, 20 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > >> b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst index
> > >> db0df7d9f27c..8df8d7fdfe70 100644
> > >> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > >> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > >> @@ -3010,6 +3010,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
> > >>
> > >> * - __u32
> > >>
> > >> - ``data_bit_offset``
> > >> - Offset (in bits) to the video data in the current slice data.
> > >>
> > >> + * - __u32
> > >> + - ``num_entry_point_offsets``
> > >> + - Specifies the number of entry point offset syntax elements in
> > >> the slice header.>
> > > This looks underdocumented. Somewhere in the docs it should be mentioned
> > > that the field 'num_entry_point_offsets' is linked to the control
> > > V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS.
> >
> > This field is here because some drivers would like know the number of
> > entry point offsets without getting the entry point offsets data itself.
>
> Yeah, this field must be set even when entry points offset control isn't used.
> Additionally, if entry point offsets control is needed and if submitting
> multiple slices at once, length of entry point offsets array must be sum of
> num_entry_point_offsets of all slices in that job. Not sure where to put this
> explanation.
>

This confused me a bit: so you mean that this field (called
num_entry_point_offsets)
must be the sum of "num_entry_point_offsets" syntax elements for
slices in the request?

If this is the case, then perhaps it will be a mistake to name our V4L2 field
exactly like the syntax element, since it this sum meaning.
Otherwise, developers would tend to get confused by it.

What do you think?

Thanks,
Ezequiel

> Best regards,
> Jernej
>
> >
> > Benjamin
> >
> > > Thanks,
> > > Ezequiel
> > >
> > >> * - __u8
> > >>
> > >> - ``nal_unit_type``
> > >> - Specifies the coding type of the slice (B, P or I).
> > >>
> > >> @@ -3150,6 +3153,14 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
> > >>
> > >> \normalsize
> > >>
> > >> +``V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (integer)``
> > >> + Specifies entry point offsets in bytes.
> > >> + This control is a dynamically sized array. The number of entry point
> > >> + offsets is reported by the ``elems`` field.
> > >> + This bitstream parameter is defined according to :ref:`hevc`.
> > >> + They are described in section 7.4.7.1 "General slice segment header
> > >> + semantics" of the specification.
> > >> +
> > >>
> > >> ``V4L2_CID_STATELESS_HEVC_SCALING_MATRIX (struct)``
> > >>
> > >> Specifies the HEVC scaling matrix parameters used for the scaling
> > >> process
> > >> for transform coefficients.
> > >>
> > >> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > >> b/drivers/media/v4l2-core/v4l2-ctrls-defs.c index
> > >> d594efbcbb93..e22921e7ea61 100644
> > >> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > >> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > >> @@ -1188,6 +1188,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> > >>
> > >> case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS: return
> "HEVC Decode
> > >> Parameters"; case V4L2_CID_STATELESS_HEVC_DECODE_MODE:
> return "HEVC
> > >> Decode Mode"; case V4L2_CID_STATELESS_HEVC_START_CODE:
> return "HEVC
> > >> Start Code";>>
> > >> + case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS: return
> "HEVC Entry
> > >> Point Offsets";>>
> > >> /* Colorimetry controls */
> > >> /* Keep the order of the 'case's the same as in v4l2-controls.h!
> */
> > >>
> > >> @@ -1518,6 +1519,10 @@ void v4l2_ctrl_fill(u32 id, const char **name,
> > >> enum v4l2_ctrl_type *type,>>
> > >> case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:
> > >> *type = V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS;
> > >> break;
> > >>
> > >> + case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:
> > >> + *type = V4L2_CTRL_TYPE_U32;
> > >> + *flags |= V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
> > >> + break;
> > >>
> > >> case V4L2_CID_STATELESS_VP9_COMPRESSED_HDR:
> > >> *type = V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR;
> > >> break;
> > >>
> > >> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> > >> index a372c184689e..3a6601a46ced 100644
> > >> --- a/include/media/hevc-ctrls.h
> > >> +++ b/include/media/hevc-ctrls.h
> > >> @@ -20,6 +20,7 @@
> > >>
> > >> #define V4L2_CID_STATELESS_HEVC_DECODE_PARAMS
> (V4L2_CID_CODEC_BASE +
> > >> 1012)
> > >> #define V4L2_CID_STATELESS_HEVC_DECODE_MODE (V4L2_CID_CODEC_BASE
> +
> > >> 1015)
> > >> #define V4L2_CID_STATELESS_HEVC_START_CODE (V4L2_CID_CODEC_BASE + 1016)
> > >>
> > >> +#define V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (V4L2_CID_CODEC_BASE
> > >> + 1017)>>
> > >> /* enum v4l2_ctrl_type type values */
> > >> #define V4L2_CTRL_TYPE_HEVC_SPS 0x0120
> > >>
> > >> @@ -316,6 +317,8 @@ struct v4l2_hevc_pred_weight_table {
> > >>
> > >> *
> > >> * @bit_size: size (in bits) of the current slice data
> > >> * @data_bit_offset: offset (in bits) to the video data in the current
> > >> slice data>>
> > >> + * @num_entry_point_offsets: specifies the number of entry point offset
> > >> syntax + * elements in the slice
> header.
> > >>
> > >> * @nal_unit_type: specifies the coding type of the slice (B, P or I)
> > >> * @nuh_temporal_id_plus1: minus 1 specifies a temporal identifier for
> > >> the NAL unit * @slice_type: see V4L2_HEVC_SLICE_TYPE_{}
> > >>
> > >> @@ -358,7 +361,7 @@ struct v4l2_hevc_pred_weight_table {
> > >>
> > >> struct v4l2_ctrl_hevc_slice_params {
> > >>
> > >> __u32 bit_size;
> > >> __u32 data_bit_offset;
> > >>
> > >> -
> > >> + __u32 num_entry_point_offsets;
> > >>
> > >> /* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
> > >> __u8 nal_unit_type;
> > >> __u8 nuh_temporal_id_plus1;
> > >>
> > >> --
> > >> 2.32.0