ffmpeg at half speed ... sort of.

[Steve O'Hara-Smith]

On Fri, 18 Feb 2005 09:56:55 -0500
Paul Chvostek <paul+fbsd at it.ca> wrote:

> 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?

	No I think it's in the low level timekeeping that usleep uses
rather than anything specific to bktr. There isn't much around that I
know of other than video capture that is particularly sensitive to
accurate usleep though. I rather suspect ACPI is screwing up fine
timekeeping. The Linux grab code also uses a timer fallback for missed
sync signals (it's a pretty common problem) but is less noisy about it
than my BSD grab code in ffmpeg.

> 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).

	Do both 4.11 and 5.3 crash with ACPI disabled ?

> > 	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.

	In a word ... bugger!

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