From 21ea3defde62fb9441049d1cea282807b7d773d4 Mon Sep 17 00:00:00 2001 From: Nicolas Dufresne Date: Tue, 9 Feb 2021 18:22:33 +0100 Subject: 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 Signed-off-by: Nicolas Dufresne Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst | 4 +++- Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) (limited to 'Documentation/userspace-api') 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 -- cgit v1.2.3-59-g8ed1b