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authorPhilipp Zabel <p.zabel@pengutronix.de>2018-11-28 16:01:21 +0300
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2018-12-07 16:17:21 +0300
commitd338e17993f78155196af4cb780d8271996a02ac (patch)
treec6ef2186898b3802fc3afe5483eb862dc1391305 /Documentation/media
parent91dc5e91edf767e27db4ee1fae19b56cd21152c0 (diff)
downloadlinux-d338e17993f78155196af4cb780d8271996a02ac.tar.xz
media: v4l2: clarify H.264 loop filter offset controls
The venus and s5p-mfc drivers add the loop filter alpha/beta offset controls V4L2_CID_MPEG_VIDEO_H264_LOOP_FILTER_ALPHA/BETA with a range of -6 to +6, inclusive. This is exactly the range specified for the slice header fields slice_alpha_c0_offset_div2 and slice_beta_offset_div2, which store half the actual filter offsets FilterOffsetA/B. Clarify that this control contains the halved offsets. Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'Documentation/media')
-rw-r--r--Documentation/media/uapi/v4l/extended-controls.rst6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/extended-controls.rst b/Documentation/media/uapi/v4l/extended-controls.rst
index 4e6255dd11a5..0b302413ab3a 100644
--- a/Documentation/media/uapi/v4l/extended-controls.rst
+++ b/Documentation/media/uapi/v4l/extended-controls.rst
@@ -1117,10 +1117,16 @@ enum v4l2_mpeg_video_h264_loop_filter_mode -
``V4L2_CID_MPEG_VIDEO_H264_LOOP_FILTER_ALPHA (integer)``
Loop filter alpha coefficient, defined in the H264 standard.
+ This value corresponds to the slice_alpha_c0_offset_div2 slice header
+ field, and should be in the range of -6 to +6, inclusive. The actual alpha
+ offset FilterOffsetA is twice this value.
Applicable to the H264 encoder.
``V4L2_CID_MPEG_VIDEO_H264_LOOP_FILTER_BETA (integer)``
Loop filter beta coefficient, defined in the H264 standard.
+ This corresponds to the slice_beta_offset_div2 slice header field, and
+ should be in the range of -6 to +6, inclusive. The actual beta offset
+ FilterOffsetB is twice this value.
Applicable to the H264 encoder.
.. _v4l2-mpeg-video-h264-entropy-mode: