Re: [xine-devel] Interesting /dev/nvidiaX vsync fact

[Stephen T. <st...@sb...>]

On Mon, 2003-03-24 at 14:30, Miguel Freitas wrote:
> hi Andrew,
>=20
> On Sun, 2003-03-23 at 19:18, Andrew de Quincey wrote:
> > If (using the binary nvidia drivers), you open /dev/nvidiaX, and then c=
all=20
> > poll() on it, you will receive a POLLPRI event every VSYNC. For systems=
 using=20
> > a single head of one of these cards, this would be an ideal way to=20
> > synchronise the vo_xv plugin to the vsync.
>=20
> have your tried to measure latency/jitter on that mechanism? what
> kernel?
> idea: you may use rdtsc instruction for a good guess...

If you really want to see jitter try a kernel that provides preemption.
I tried it and a stream that plays smoothly on a vanilla 2.4.18 kernel
shows jitter/latency on a preemption enabled kernel. I use KURT Linux,
http://www.ittc.ku.edu/kurt, for testing RT software.

Stephen
--=20
Stephen Torri <st...@sb...>