On Thu, 18 Oct 2001, Billy Biggs wrote:
> Hi Mark (and list), apologies for keeping traffic so high, but I have
> another question about XVideo and it's just too useful. :)
>
> Say I'm attemping to play 525/59.94 video (identical problem exists
> for 625/50 systems). Ideally, I want to do software deinterlacing and
> output full 720x486 images at 59.94fps. However, PCs are still slow, so
> my application has three choices:
>
> a) full resolution 59.94 deinterlaced,
> b) half-resolution 59.94 (using Xv for scaling up each field),
> c) full-resolution 29.97 deinterlaced.
>
> Dealing with (a) and (c) is easy, but (b) is ambiguous. I see two
> basic methods:
>
> Method 1: Create Xv images of size 720x240. Make sure the scaling of
> the window is such that input scanlines are aligned to output scanlines.
>
> o Blit top fields to x,y of 0,0, w,h of 720,485 (scaled)
> o Blit bottom fields to x,y of 0,1, w,h of 720,486 (scaled)
>
> Problems:
>
> 1) Since I usually get input as frames, I need to do an extra copy to
> split the input into the two field buffers. This is really, really
> awkward since at least for DVDs we often switch between progressive
> and interlaced input. With the i810 at least, any time I start
> blitting images of a new size, the card resets and I get a few bad
> frames blit before it wakes up! :( (is this a bug?)
>
> It seems to me that the Xv API could have benefited from a pixel
> stride parameter for blits. Is this fixable?
It's possible for the driver to offer a port attribute with
top/bottom. Maybe it's best that it's write only and applies
only to the next command. It could work like a hint for the next
PutImage. XvMC has explicit top/bottom/frame instructions in the
Put command.
Mark.
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