Subject: Re: [PATCH v2 3/4] media: uapi: hevc: Add segment address field

From: Mauro Carvalho Chehab <[email-masked]>
Date: Wed, 8 Jan 2020 15:31:26 +0100

Em Fri, 13 Dec 2019 17:04:27 +0100
Jernej Skrabec <[email-masked]> escreveu:

> If HEVC frame consists of multiple slices, segment address has to be
> known in order to properly decode it.
> 
> Add segment address field to slice parameters.
> 
> Signed-off-by: Jernej Skrabec <[email-masked]>
> ---
>  Documentation/media/uapi/v4l/ext-ctrls-codec.rst | 5 ++++-
>  include/media/hevc-ctrls.h                       | 5 ++++-
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
> index aab1451e54d4..5415d5babcc2 100644
> --- a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
> @@ -3975,6 +3975,9 @@ 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
> +      - ``slice_segment_addr``
> +      -
>      * - __u8
>        - ``nal_unit_type``
>        -
> @@ -4052,7 +4055,7 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>        - ``num_rps_poc_lt_curr``
>        - The number of reference pictures in the long-term set.
>      * - __u8
> -      - ``padding[7]``
> +      - ``padding[5]``
>        - Applications and drivers must set this to zero.
>      * - struct :c:type:`v4l2_hevc_dpb_entry`
>        - ``dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> index 1592e52c3614..3e2e32098312 100644
> --- a/include/media/hevc-ctrls.h
> +++ b/include/media/hevc-ctrls.h
> @@ -167,6 +167,9 @@ struct v4l2_ctrl_hevc_slice_params {
>  	__u32	bit_size;
>  	__u32	data_bit_offset;
>  
> +	/* ISO/IEC 23008-2, ITU-T Rec. H.265: General slice segment header */
> +	__u32	slice_segment_addr;
> +

Why are you adding it in the middle of the data? This will break any 
existing userspace code that might be relying on it.

Ok, I know that this header is not yet under include/uapi,and there's a
warning on it for letting people know that it shouldn't be used anywhere.

Still, people might be using it.

>  	/* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
>  	__u8	nal_unit_type;
>  	__u8	nuh_temporal_id_plus1;
> @@ -200,7 +203,7 @@ struct v4l2_ctrl_hevc_slice_params {
>  	__u8	num_rps_poc_st_curr_after;
>  	__u8	num_rps_poc_lt_curr;
>  
> -	__u8	padding;
> +	__u8	padding[5];
>  
>  	/* ISO/IEC 23008-2, ITU-T Rec. H.265: General slice segment header */
>  	struct v4l2_hevc_dpb_entry dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];

Cheers,
Mauro

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