Wed, 17 Jan 2001 Cort Dougan wrote:
> } Problem is, I need an understanding of how useful
> } this would be to people. My requirements troll
> } on linux-audio-dev doesn't seem to have elicited
> } a response.
> }
> } Do we need it? If so, how bad?
>
> Be sure to send this to the FB console list. They've been looking for a
> solution for over a year.
What about retrace sync? (Which is not in the mainstream fbcon, as it's
inherently horrible code on most cards.)
I have a solution that "kind of" works even if SCHED_FIFO threads are allowed
to preempt the retrace polling loop every now and then - the only impact will
be that whoever uses the retrace sync ioctl will (obviously) return a little
late, depending on how nasty the SCHED_FIFO threads are. (Not if the video
thread has higher priority, of course!)
The current implementation simply uses the Pentium performance counter to keep
track of when the next retrace should occur, syncing the internal "milliframe"
time to the video card whenever it actually gets a chance to see the retrace
bit.
This could probably be extended to use some kind of kernel timers, but I'm
not sure how reliable that would be from the video perspective. (When using
real hardware pageflipping as opposed to blitting, you *can't* be late. If you
are, you'll simply miss a frame!)
Then again, as we're talking about lowlatency here, this could actually work
pretty well if done right.
//David
..- M A I A -------------------------------------------------.
| Multimedia Application Integration Architecture |
| A Free/Open Source Plugin API for Professional Multimedia |
`----------------------> http://www.linuxaudiodev.com/maia -'
..- David Olofson -------------------------------------------.
| Audio Hacker - Open Source Advocate - Singer - Songwriter |
`--------------------------------------> [EMAIL PROTECTED] -'
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