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.
Cheers,
Paul
>
> Return Value
> diff --git a/Documentation/media/videodev2.h.rst.exceptions
> b/Documentation/media/videodev2.h.rst.exceptions
> index 55cbe324b9fc..74fb9f00c12d 100644
> --- a/Documentation/media/videodev2.h.rst.exceptions
> +++ b/Documentation/media/videodev2.h.rst.exceptions
> @@ -180,6 +180,7 @@ replace define V4L2_PIX_FMT_FLAG_PREMUL_ALPHA
> reserved-formats
> # V4L2 format flags
> replace define V4L2_FMT_FLAG_COMPRESSED fmtdesc-flags
> replace define V4L2_FMT_FLAG_EMULATED fmtdesc-flags
> +replace define V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER fmtdesc-flags
>
> # V4L2 tymecode types
> replace define V4L2_TC_TYPE_24FPS timecode-type
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 2427bc4d8eba..8c5a28666b16 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -774,8 +774,9 @@ struct v4l2_fmtdesc {
> __u32 reserved[4];
> };
>
> -#define V4L2_FMT_FLAG_COMPRESSED 0x0001
> -#define V4L2_FMT_FLAG_EMULATED 0x0002
> +#define V4L2_FMT_FLAG_COMPRESSED 0x0001
> +#define V4L2_FMT_FLAG_EMULATED 0x0002
> +#define V4L2_FMT_FLAG_HAS_BITSTREAM_PARSER 0x0004
>
> /* Frame Size and frame rate enumeration */
> /*
> --
> 2.20.1
>
--
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
