Commit 4245232f authored Aug 25, 2020 by Ezequiel Garcia Committed by Mauro Carvalho Chehab Sep 01, 2020

media: uapi: h264: Increase size of 'first_mb_in_slice' field



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.

Although unlikely, a 8192x4320 video (where macroblocks are 16x16),
would contain 138240 macroblocks on a frame.

As per the H264 specification, 'first_mb_in_slice' can be up to
PicSizeInMbs - 1, so increase the size of the field to 32-bits.

Note that v4l2_ctrl_h264_slice_params struct will be modified
in a follow-up commit, and so we defer its 64-bit padding.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Tested-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

parent fb92c563

Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst

+1 −1

Original line number	Diff line number	Diff line
		@@ -1774,7 +1774,7 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
		* - __u32
		- ``header_bit_size``
		-
		* - __u16
		* - __u32
		- ``first_mb_in_slice``
		-
		* - __u8

include/media/h264-ctrls.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -172,7 +172,8 @@ 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;

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