On Fri, 19 Oct 2001, Billy Biggs wrote:
> Mark Vojkovich ([EMAIL PROTECTED]):
>
> > It doesn't work that way. There's no such thing as subpixel
> > destinations so you have to stop thinking about it that way. You have
> > integer rectangles on the screen but you can align how the source
> > scales to that. You can essentially assign the corners of that screen
> > aligned rectangle to subpixel points within the source. I can have
> > the top line of the destination display not the top line of the source
> > but adjust the filter kernel so that it starts displaying, for
> > example, 5/16 of the way between the first and second lines of the
> > source, effectively shifting the whole image up by 5/16 of a pixel. I
> > have subpixel alignment of the source within the destination
> > rectangle.
> >
> > I have not seen any hardware which cannot do this.
>
> Ok, awesome! Makes sense. So, should I start by adding this to the
> i810 or something? I bet I could figure that out. So should we maybe
There's probably already code that does that in the i810's
XvMC driver. You could add it or Matthew Sottek could if he
had time.
> standardize on XV_DISPLAY_FIELD and implement that everywhere? I'd like
I like that name. Maybe somebody else has a better suggestion.
> to see this implemented ASAP as I know both my code and at least
> mjpegtools code (if not all video players) could benefit from this.
>
> Seems slightly inconsistent with XvMC's signalling though. Or we can
> use the same type:
>
> #define XVMC_TOP_FIELD 0x00000001
> #define XVMC_BOTTOM_FIELD 0x00000002
> #define XVMC_FRAME_PICTURE (XVMC_TOP_FIELD | XVMC_BOTTOM_FIELD)
That's mpeg's picture structure flags. We could use that
but I think the gaps are a little awkward. There is some other
0=top, 1=bottom precedence with things like mpeg's
motion_vertical_field_select.
If it's allowing stuff like frame display, the name XV_DISPLAY_FIELD
probably isn't appropriate. And I don't know what a value of zero
is supposed to do.
>
> > > > With write-only port attributes you can essentially extend the
> > > > Xv(Shm)PutImage function by specifying additional attributes
> > > > before the request. An attribute such as XV_DISPLAY_FIELD could
> > > > be set to indicate that the next Put request is to be a field.
> > > > The value would be 0=top, 1=bottom in MPEG fashion. It's a
> > > > one-shot thing and only applies to the next put. All drivers
> > > > could add this without API or protocol changes.
> > >
> > > Yes, this would be ideal.
Mark.
_______________________________________________
Xpert mailing list
[EMAIL PROTECTED]
http://XFree86.Org/mailman/listinfo/xpert
