Re: Re: [PATCH v6 11/17] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS control

Jernej Škrabec
2022-05-31T18:20:45Z

Dne torek, 31. maj 2022 ob 08:58:46 CEST je Benjamin Gaignard napisal(a):
>
> Le 30/05/2022 à 23:24, Jernej Škrabec a écrit :
> > Dne ponedeljek, 30. maj 2022 ob 15:49:57 CEST je Hans Verkuil napisal(a):
> >> On 30/05/2022 11:18, Hans Verkuil wrote:
> >>> On 29/05/2022 08:40, Jernej Škrabec wrote:
> >>>> Hi!
> >>>>
> >>>> This series looks very good and I plan to test it shortly on Cedrus,
but
> > I
> >>>> have one major concern below.
> >>>>
> >>>> Dne petek, 27. maj 2022 ob 16:31:28 CEST je Benjamin Gaignard
napisal(a):
> >>>>> 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.
> >>>> Slice control by itself is variable length array, so you would actually
> > need
> >>>> 2D variable array for entry points which is not supported. However,
easy
> >>>> workaround for that is to flatten 2D array to 1D and either have another
> > slice
> >>>> control field which would tell first entry point index for convenience or
> > let
> >>>> driver calculate it by adding up all num_entry_point_offsets of previous
> >>>> slices.
> >>>>
> >>>> Hans, what do you think?
> >>> If I would support 2D variable array sizes, wouldn't that be more
elegant?
> >>>
> >>> The current implementation doesn't support that, but as the commit log
for
> >>> patch 1/17 says:
> >>>
> >>> "Currently dynamically sized arrays are limited to one dimensional
arrays,
> >>> but that might change in the future if there is a need for it."
> >>>
> >>> Let me know if you agree, and I'll try to implement this. It's been a
> > while
> >>> since I last looked at this, so I'm not sure how much work it is, but it
> > is
> >>> probably worth a shot.
> >> Digging more into this made me realize that this doesn't actually help
for
> > this
> >> particular case.
> >>
> >> I would lean towards your second suggestion of adding up all
> > num_entry_point_offsets
> >> of previous slices.
> > Just one question/clarification about dynamic arrays - does driver need to
> > reserve maximum amount of memory for dynamic array control at
initialization
> > time? If so, this would still be problematic, since there cound be a huge
> > amount of entry points in theory.
>
> When adding the control the driver could set .dims field to specify
> the max number of accepted slices.
> I have added '#define V4L2_HEVC_SLICE_MAX_COUNT 600' that you could use
> for this field. It is the value we have found when using slices with RKVDEC
> driver.

Is this maximum value applicable only to RKVDEC or is universal? Anyway, this
means maximum offset points control for Cedrus would be 600 * 1024 (max. offset
points supported per slice) * 4 ~= 2.4 MB, which is a lot for one control, but
I can live with that...

Best regards,
Jernej

>
> Regards,
> Benjamin
>
> >
> > Best regards,
> > Jernej
> >
> >> Regards,
> >>
> >> Hans
> >>
> >>> Regards,
> >>>
> >>> Hans
> >>>
> >>>> Note, it seems that H265 decoding on Cedrus still works without entry
> > points,
> >>>> so this problem can be solved later. I'm not sure what we lose with
that
> > but
> >>>> it was suggested that this could influence speed or error resilience or
> > both.
> >>>> However, I think we're close to solve it, so I'd like to do that now.
> >>>>
> >>>> Best regards,
> >>>> Jernej
> >>>>
> >>>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.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 0796b1563daa..05228e280f66 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.
> >>>>> * - __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 a3c829ef531a..1319cb99ae3f 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
> >>>>> @@ -318,6 +319,8 @@ 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_{}
> >>>>> @@ -360,7 +363,7 @@ 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
> >>>>>
> >>>>>
> >>>>
> >>
> >
>