Re: [RFC 4/7] media: uapi: h264: increase size of fields

[Ezequiel Garcia <ezequiel@collabora.com>]

On Thu, 2020-06-25 at 11:01 -0400, Nicolas Dufresne wrote:
> Le mardi 23 juin 2020 à 15:28 -0300, Ezequiel Garcia a écrit :
> > Slice header syntax element 'first_mb_in_slice' can point
> > to the last macroblock, currently the field can only reference
> > 65536 macroblocks which is insufficient for 8K videos.
> > 
> > DPB entry PicNum maximum value is 2*MaxFrameNum for interlaced
> > content (field_pic_flag=1).
> > 
> > Therefore, increase 'first_mb_in_slice' and 'pic_num'.
> > 
> > The v4l2_h264_dpb_entry struct needs to be padded to avoid a hole,
> > which will be useful to allow future uAPI extensions.
> > 
> > Note that v4l2_ctrl_h264_slice_params struct will be modified
> > in a follow-up commit, and so we defer its 64-bit padding.
> 
> This patch includes two changes, with two distinct rationale. Please
> split in two, I would also add reference to the spec in the commit
> messages.

OK.

> The explanation is also insufficient. Need to mention that
> macro-blocks are 16x16, and the bounds for synthetic value
> MaxFrameNum (derived from bitstream value) has not be mention either.
> 

OK, will do.

Thanks!
Ezequiel

> > Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> > ---
> >  .../userspace-api/media/v4l/ext-ctrls-codec.rst          | 7 +++++--
> >  drivers/media/v4l2-core/v4l2-ctrls.c                     | 9 +++++++++
> >  include/media/h264-ctrls.h                               | 6 ++++--
> >  include/media/v4l2-h264.h                                | 2 +-
> >  4 files changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > index 0808a36777b6..e3b5a28fb965 100644
> > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > @@ -1772,7 +1772,7 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
> >      * - __u32
> >        - ``header_bit_size``
> >        -
> > -    * - __u16
> > +    * - __u32
> >        - ``first_mb_in_slice``
> >        -
> >      * - __u8
> > @@ -2046,7 +2046,10 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
> >      * - __u16
> >        - ``frame_num``
> >        -
> > -    * - __u16
> > +    * - __u8
> > +      - ``reserved[6]``
> > +      - Applications and drivers must set this to zero.
> > +    * - __u32
> >        - ``pic_num``
> >        -
> >      * - __s32
> > diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> > index 6abd023f10c7..a751c14f9c22 100644
> > --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> > +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> > @@ -1734,6 +1734,7 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
> >  	struct v4l2_ctrl_mpeg2_slice_params *p_mpeg2_slice_params;
> >  	struct v4l2_ctrl_vp8_frame_header *p_vp8_frame_header;
> >  	struct v4l2_ctrl_h264_slice_params *p_h264_slice_params;
> > +	struct v4l2_ctrl_h264_decode_params *p_h264_dec_params;
> >  	struct v4l2_ctrl_hevc_sps *p_hevc_sps;
> >  	struct v4l2_ctrl_hevc_pps *p_hevc_pps;
> >  	struct v4l2_ctrl_hevc_slice_params *p_hevc_slice_params;
> > @@ -1808,6 +1809,14 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
> >  		}
> >  		break;
> >  	case V4L2_CTRL_TYPE_H264_DECODE_PARAMS:
> > +		p_h264_dec_params = p;
> > +
> > +		for (i = 0; i < V4L2_H264_NUM_DPB_ENTRIES; i++) {
> > +			struct v4l2_h264_dpb_entry *dpb_entry =
> > +				&p_h264_dec_params->dpb[i];
> > +
> > +			zero_reserved(*dpb_entry);
> > +		}
> >  		break;
> >  
> >  	case V4L2_CTRL_TYPE_VP8_FRAME_HEADER:
> > diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
> > index c6cbf178c1c9..a938d16b901c 100644
> > --- a/include/media/h264-ctrls.h
> > +++ b/include/media/h264-ctrls.h
> > @@ -161,7 +161,8 @@ struct v4l2_ctrl_h264_slice_params {
> >  	/* Offset in bits to slice_data() from the beginning of this slice. */
> >  	__u32 header_bit_size;
> >  
> > -	__u16 first_mb_in_slice;
> > +	__u32 first_mb_in_slice;
> > +
> >  	__u8 slice_type;
> >  	__u8 pic_parameter_set_id;
> >  	__u8 colour_plane_id;
> > @@ -208,7 +209,8 @@ struct v4l2_ctrl_h264_slice_params {
> >  struct v4l2_h264_dpb_entry {
> >  	__u64 reference_ts;
> >  	__u16 frame_num;
> > -	__u16 pic_num;
> > +	__u8 reserved[6];
> > +	__u32 pic_num;
> >  	/* Note that field is indicated by v4l2_buffer.field */
> >  	__s32 top_field_order_cnt;
> >  	__s32 bottom_field_order_cnt;
> > diff --git a/include/media/v4l2-h264.h b/include/media/v4l2-h264.h
> > index bc9ebb560ccf..1a5f26fc2a9a 100644
> > --- a/include/media/v4l2-h264.h
> > +++ b/include/media/v4l2-h264.h
> > @@ -33,7 +33,7 @@ struct v4l2_h264_reflist_builder {
> >  	struct {
> >  		s32 pic_order_count;
> >  		int frame_num;
> > -		u16 pic_num;
> > +		u32 pic_num;
> >  		u16 longterm : 1;
> >  	} refs[V4L2_H264_NUM_DPB_ENTRIES];
> >  	s32 cur_pic_order_count;