On Sat, Jul 27, 2019 at 6:37 PM Paul Kocialkowski <paul.kocialkow...@bootlin.com> wrote: > > Hi, > > On Wed 24 Jul 19, 13:05, Hans Verkuil wrote: > > Add an enum_fmt format flag to specifically tag coded formats where > > full bitstream parsing is supported by the device. > > > > Some stateful decoders are capable of fully parsing a bitstream, > > but others require that userspace pre-parses the bitstream into > > frames or fields (see the corresponding pixelformat descriptions > > for details). > > > > If this flag is set, then this pre-parsing step is not required > > (but still possible, of course). > > > > Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl> > > --- > > Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 8 ++++++++ > > Documentation/media/videodev2.h.rst.exceptions | 1 + > > include/uapi/linux/videodev2.h | 5 +++-- > > 3 files changed, 12 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > > b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > > index 822d6730e7d2..4e24e671f32e 100644 > > --- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > > +++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst > > @@ -127,6 +127,14 @@ one until ``EINVAL`` is returned. > > - This format is not native to the device but emulated through > > software (usually libv4l2), where possible try to use a native > > format instead for better performance. > > + * - ``V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER`` > > + - 0x0004 > > + - The hardware decoder for this compressed bitstream format (aka > > coded > > + format) is capable of parsing the bitstream. Applications do not > > + need to parse the bitstream themselves to find the boundaries between > > + frames/fields. This flag can only be used in combination with the > > + ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to compressed > > + formats only. > > Should this flag be set for stateless codecs as well? It seems a bit over-kill > for this case. I am not sure whether "compressed bitstream format" clearly > only > covers the formats used by stateful decoders and not the ones for stateless > decoders.
I'd suggest using a different name for the flag, because "bitstream parser" is actually one of the core differences between stateful and stateless. All stateful decoders have bitstream parsers, the only difference between the implementations is the unit on which the parser operates, i.e. full stream, frame, NALU. Perhaps V4L2_FMT_FLAG_CONTINUOUS_BITSTREAM (as opposed to discrete, framed/sliced chunks)? Regardless of that, it doesn't make sense for a stateless decoder to set this flag anyway, because the userspace needs to parse the whole stream anyway and the whole stateless API is based on the assumption that the userspace splits the bitstream into frames (or slices). Best regards, Tomasz
