Messages in this thread | | | Date | Tue, 31 May 2022 08:58:46 +0200 | Subject | Re: [PATCH v6 11/17] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS control | From | Benjamin Gaignard <> |
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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.
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 >>>>> >>>>> >>>> >> >
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