[mythtv] Ticket #6938: smoother playback

[Mark Spieth]

>Strange.  I had a lot of tearing when I used an integrated 6150 and a
>discreet 6200.  I'm now using an integrated 9400 and tried again last
>night.  There's not near as much tearing as before, but there's still
>some.
>
>Anyway, if no one objects to saying this "fixes jerky timestretching",
>I'm willing to commit it.  IOW, it's as much a bug fix as it is an
>enhancement sine we are in a feature freeze.

I cant vouch for the other vsync modes.
gigem said it was worse with RTC sync method and vdpau, though Im not sure 
why that would be.

be nice to get some other config tests too for reasonable coverage.
or put in a config flag for mode selection so it doesnt break anything worst 
case.

but tearing means I got rid of RTC mode long ago.

cheers
mark