On Thu, 20 Sep 2001, Peter Surda wrote:
> On Wed, Sep 19, 2001 at 07:52:16PM -0700, Mark Vojkovich wrote:
> > > I'd like to propose a change to Xv standard, to add a function
> > > "XvGetImage",
> > > which could be used to transfer data from videoram to system memory.
> 2
> > > possible situations it can be used:
> > What's the prototype look like. Ie, what's the source. Port
> > or Drawable?
> Hmm I haven't gone so far yet, I'd like to find out first whether my
> idea has
> support in general or not.
>
> I'm looking at R128's XvPutVideo function now, and I think the proposed
> XvGetVideo should look similarly, but instead of copying the data from
> bt829
> to a different place in video memory and telling the card to perfom YUV
> conversion and scaling, it should be copied into userspace. Hence it
> seems to
> be more reasonable to have Port as a source, as it will allow to capture
> without displaying something which actually is what I want.
>
Then the client API would be the same as XvGetStill but would use
an XvImage as the destination instead of a Drawable. That's a fine
API addition. Having the Bt829 copy the data to system memory
has implemenation issues though. Kernel support is required to
make sure the XvImage is swapped in and locked down while the
hardware dumps data to it. That's primarily why something like
that hasn't been added.
Mark.
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