On 8/12/19 1:56 PM, Ezequiel Garcia wrote: > On Mon, 2019-08-12 at 12:11 +0200, Hans Verkuil wrote: >> On 8/8/19 12:34 PM, Ezequiel Garcia wrote: >>> Stateless decoders have different expectations about the >>> start code that is prepended on H264 slices. Add a >>> menu control to express the supported start code types >>> (including no start code). >>> >>> Drivers are allowed to support only one start code type, >>> but they can support both too. >>> >>> Note that this is independent of the H264 decoding mode, >>> which specifies the granularity of the decoding operations. >>> Either in frame-based or slice-based mode, this new control >>> will allow to define the start code expected on H264 slices. >>> >>> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> >>> --- >>> Changes in v4: >>> * New patch. >>> --- >>> .../media/uapi/v4l/ext-ctrls-codec.rst | 31 +++++++++++++++++++ >>> drivers/media/v4l2-core/v4l2-ctrls.c | 9 ++++++ >>> include/media/h264-ctrls.h | 6 ++++ >>> 3 files changed, 46 insertions(+) >>> >>> diff --git a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst >>> index ea0455957149..94fd3a9b8b9e 100644 >>> --- a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst >>> +++ b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst >>> @@ -2062,6 +2062,37 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type - >>> The OUTPUT buffer should contain all slices needed to decode the >>> frame/field. >>> >>> +``V4L2_CID_MPEG_VIDEO_H264_STARTCODE (enum)`` >>> + Specifies the H264 slice start code expected for each slice. >>> + This control shall e used to complement V4L2_PIX_FMT_H264_SLICE >> >> e -> be >> >>> + pixel format. Drivers may expose a single or multiple >>> + start codes, depending on what they can support. >>> + >>> + .. note:: >>> + >>> + This menu control is not yet part of the public kernel API and >>> + it is expected to change. >>> + >>> +.. c:type:: v4l2_mpeg_video_h264_startcode >>> + >>> +.. cssclass:: longtable >>> + >>> +.. flat-table:: >>> + :header-rows: 0 >>> + :stub-columns: 0 >>> + :widths: 1 1 2 >>> + >>> + * - ``V4L2_MPEG_VIDEO_H264_NO_STARTCODE`` >>> + - 0 >>> + - Selecting this value specifies that H264 slices are passed >>> + to the driver without any start code. >>> + Bla. >> >> Bla? >> > > Well, despite how many times I reviewed this doc, it seems > this slipped through :-( > >>> + * - ``V4L2_MPEG_VIDEO_H264_ANNEX_B_STARTCODE`` >>> + - 1 >>> + - Selecting this value specifies that H264 slices are expected >>> + to be prefixed by Annex B start codes. According to :ref:`h264` >>> + valid start codes can be 3-bytes 0x000001, or 4-bytes 0x00000001. >>> + >> >> I had the impression that it is more common to require startcodes. If that's >> indeed the case, shouldn't this have value 0 instead of 1? >> 1? >> > > I'm not sure this is indeed the case. > > For instance, VA-API accelerators work on H264 slices that are not > prepended by the NALU start code. > > I'm fine flipping the values, but at this point, with only cedrus and hantro, > there's doesn't seem to be a "natural" choice. OK, let's keep this as-is then. Regards, Hans > > Thanks, > Ezequiel > _______________________________________________ Linux-rockchip mailing list Linux-rockchip@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-rockchip
