ffmpeg at half speed ... sort of.

[Paul Chvostek]

On Mon, Feb 14, 2005 at 10:23:31AM +0000, Steve O'Hara-Smith wrote:
> 
> > or is the sync signal merely a timer?  Could this be a problem
> > with the frequency of the sync signal coming from the driver?  Does the
> > driver time its sync signals based on the hardware, or something else?
> 
> 	The driver gets it's sync signals from the incoming video field sync.

So ... if the same video signal and same hardware shows these wildly
inconsistent framerates encoding with ffmpeg in FreeBSD but not in
Fedora, it's likely a problem in the bktr driver?

If it's a bug in the driver, it seems odd that I'd be the first person
to experience this.  I see there have been some fairly recent changes to
bktr_core.c, but I'm not sure whether they're timing related.

> > > 	Do you get any of the SLEPT ... messages ?
> > 
> > Plenty of them.  From five to ten for every notice as to what frame I've
> > reached,
> 
> 	That's not good - probable causes for that many are lousy signal or bad
> timekeeping - given the other symptoms I strongly suspect bad timekeeping.

I get the same behaviour with multiple video sources (both analog and
digital satellite video decoders, a handycam, a VCR, various cables) and
multiple encoder cards (AVerMedia cx878 and an old Intel bt848) ...  and
of course, as I said, the problem seems exclusive to FreeBSD (tested
with both 4.11 and 5.3).

If the bad timekeeping you suspect is just in the bktr driver ... is
there anything else I can do to help identify what needs to be fixed?
Alas, I'm not equipped to help much with actual driver programming.

> > kern.timecounter.hardware: ACPI-fast
> > kern.timecounter.choice: TSC(800) ACPI-fast(1000) i8254(0) dummy(-1000000)
> 
> 	kern.timecounter.hardware should be the one - from the looks of it. Try setting
> it to TSC or i8254 (probably TSC will do a better job).

Tried both, to no avail; the symptoms remain.

> 	It might be worth checking on Hyperthreading having an effect.

No effect that I can see.

-- 
  Paul Chvostek                                             <paul at it.ca>
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