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authorNicolas Dufresne <nicolas.dufresne@collabora.com>2021-02-09 18:22:33 +0100
committerMauro Carvalho Chehab <mchehab+huawei@kernel.org>2021-03-11 11:59:42 +0100
commit21ea3defde62fb9441049d1cea282807b7d773d4 (patch)
treec64b18efb0d4a238e17f10304195d136cd30f09e /Documentation/userspace-api
parent6a49401e15b5ea41503a6905f99f3b32f0a534fb (diff)
media: doc: h264/hevc: Clarify _START_CODE_NONE meaning
As some hardware have a knob to enable or disable emulation prevention bytes removal, driver writers ended up wondering what exactly the START_CODE_NONE modes meant in this regards. This patch clarify what is expected with a reference to the specification. Reported-by: John Cox <jc@kynesim.co.uk> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Diffstat (limited to 'Documentation/userspace-api')
-rw-r--r--Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst4
-rw-r--r--Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst4
2 files changed, 6 insertions, 2 deletions
diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
index 681f59e0a8f5..90c0e1d57544 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
@@ -769,7 +769,9 @@ Stateless Codec Control ID
* - ``V4L2_STATELESS_H264_START_CODE_NONE``
- 0
- Selecting this value specifies that H264 slices are passed
- to the driver without any start code.
+ to the driver without any start code. The bitstream data should be
+ according to :ref:`h264` 7.3.1 NAL unit syntax, hence contains
+ emulation prevention bytes when required.
* - ``V4L2_STATELESS_H264_START_CODE_ANNEX_B``
- 1
- Selecting this value specifies that H264 slices are expected
diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
index 76ebf86b9d0b..7ee8ae073b91 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
@@ -3719,7 +3719,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
* - ``V4L2_MPEG_VIDEO_HEVC_START_CODE_NONE``
- 0
- Selecting this value specifies that HEVC slices are passed
- to the driver without any start code.
+ to the driver without any start code. The bitstream data should be
+ according to :ref:`hevc` 7.3.1.1 General NAL unit syntax, hence
+ contains emulation prevention bytes when required.
* - ``V4L2_MPEG_VIDEO_HEVC_START_CODE_ANNEX_B``
- 1
- Selecting this value specifies that HEVC slices are expected