Re: [RFC] media: uapi: Add VP8 low-level decoder API compound controls.

[Tomasz Figa <tfiga@chromium.org>]

On Fri, Feb 15, 2019 at 9:06 AM Ezequiel Garcia <ezequiel@collabora.com> wrote:
>
> On Wed, 2019-02-13 at 21:35 -0500, Nicolas Dufresne wrote:
> > Le mer. 13 févr. 2019 à 16:23, Ezequiel Garcia
> > <ezequiel@collabora.com> a écrit :
> > > Hi,
> > >
> > > On Wed, 2019-02-13 at 18:15 -0300, Ezequiel Garcia wrote:
[snip]
> > > > +     __u8 version;
> > > > +
> > > > +     /* Populated also if not a key frame */
> > > > +     __u16 width;
> > > > +     __u16 height;
> > > > +     __u8 horizontal_scale;
> > > > +     __u8 vertical_scale;
> > > > +
> > > > +     struct v4l2_vp8_segment_header segment_header;
> > > > +     struct v4l2_vp8_loopfilter_header lf_header;
> > > > +     struct v4l2_vp8_quantization_header quant_header;
> > > > +     struct v4l2_vp8_entropy_header entropy_header;
> > > > +
> > > > +     __u8 sign_bias_golden;
> > > > +     __u8 sign_bias_alternate;
> > > > +
> > > > +     __u8 prob_skip_false;
> > > > +     __u8 prob_intra;
> > > > +     __u8 prob_last;
> > > > +     __u8 prob_gf;
> > > > +
> > > > +     __u32 first_part_size;
> > > > +     __u32 first_part_offset; // this needed? it's always 3 + 7 * s->keyframe;
> > >
> > > As the comment says, it seems the first partition offset is always
> > > 3 + 7 * s->keyframe. Or am I wrong?
> >
> > I can't find it in VA API or GStreamer parsers. Ideally we need to
> > look in the spec, if it's calculated it does not belong here.
> >
>
> Looking into the spec, I don't think it's part of it.
>
> > https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/blob/master/gst-libs/gst/codecparsers/gstvp8parser.h#L255
> > https://github.com/intel/libva/blob/master/va/va_dec_vp8.h#L72
> >
> > Notice that VA splits this in two, the some part in the picture
> > parameter, and some parts as SliceParameters. I believe it's to avoid
> > having conditional field base on if key_frame == 0.
> >
>
> That might make sense. Something to look into.

Yeah, sounds reasonable, although VAAPI naming is a bit off, since VP8
doesn't have a notion of slices...

Best regards,
Tomasz