[PATCH v3 1/3] media: uapi: h264: Clarify our expectations regarding NAL header format

Boris Brezillon
2019-07-03T12:28:56Z

Looks like some stateless decoders expect slices to be prefixed with
ANNEX B start codes (they most likely do some kind of bitstream parsing
and/or need that to delimit slices when doing per frame decoding).
Since skipping those start codes for dummy stateless decoders (those
expecting all params to be passed through controls) should be pretty
easy, let's mandate that all slices be prepended with ANNEX B start
codes.

If we ever need to support AVC headers, we can add a new menu control
to select the type of NAL header to use.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
Changes in v3:
* Add Paul's R-b

Changes in v2:
* None
---
Documentation/media/uapi/v4l/ext-ctrls-codec.rst | 1 +
1 file changed, 1 insertion(+)

diff --git a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
index 7a1947f5be96..3ae1367806cf 100644
--- a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
+++ b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
@@ -1726,6 +1726,7 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
:ref:`h264`, section 7.4.3 "Slice Header Semantics". For further
documentation, refer to the above specification, unless there is
an explicit comment stating otherwise.
+ All slices should be prepended with an ANNEX B start code.

.. note::

--
2.21.0