BSD video capture emulation question

Steve O'Hara-Smith steve at
Thu Jul 10 22:09:27 PDT 2003

On Thu, 10 Jul 2003 13:40:47 -0700
John-Mark Gurney <gurney_j at> wrote:

JMG> Yes, I followed the bktr interface, but the bktr interface needs to
JMG> disappear ASAP!  The bktr interface is very bad as we make FreeBSD
JMG> multiplatform.  It lets the user supply the physical address when
JMG> doing video overlay to the video card.  This should be handled by the
JMG> driver, not the userland app.

	Hmm, that implies that the driver must know how to find the
overlay area that the userland app wants it to use - irrespective of the
video out driver in use.

	Conclusion the overlay areas have to be entities of some kind in
the in the multimedia infrastructure. 

JMG> > 	AFAICS what's needed is someone with some insight into what makes
JMG> > a good video API if FreeBSD is ever going to get one. The innards
JMG> > of things like ffmpeg and transcode are probably worth looking at
JMG> > as models.
JMG> Hmmm.  I'll have to look at that.
JMG> But there is more than just codec handling.  One of the features that

	Oh sure - but seamless plumbing of codecs, sources and sinks is
a very desirable feature IMHO. This is the bit that these apps seem to

JMG> the Zoran card supports is the ability to have two sources (since as
JMG> external video and MJPEG playback) one in a window of the other.  But
JMG> you need to only have one video clock running the output.  This
JMG> should be handled by the video api so the drivers just write the raw
JMG> interface and the api does the manipulation of the driver.

	Yep seamless plumbing - so somehow the PIP has to present as a video
sink and DTRT when you plumb the other video source into it - even if that
turns out to be the output of mplayer playing a VCD and not the expected
other bit from the card. If it can't do it the plumbing must fail.

	ISTM the plumbing actions either require a smart plumber or a
dialogue between the interfaces being plumbed. The latter seems to fit
the UNIX device model better.

	Are thinking in similar terms ?

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