[ardour-users] noise during playback

[Steven Chamberlain]

> I have investigated about xruns, and I think this is not the cause.
> The xruns happen sometimes when I minimize/maximize the window, and a
> big click/pop is heard. But the noise I am talking about is more
> continuous and not so loud (and has no xrun associated).

I used to suffer from this; even when I was getting no xruns reported, I
could still get clicks on any audio playback through JACK.  I think it
was related to the sound card's interrupts not being handled quickly
enough (causing some underrun which ALSA or JACK seemed to be unaware of).

I believe the problem is (or was) particularly bad on motherboards with
a VIA chipset, though I believe your chipset is Intel.  I had no luck
fixing this problem before and just waited until I could afford an
nForce4 though I'm not sure if that changed much.

What I currently do is use an '-rt' patched kernel and configure IRQ
priorities just from my boot scripts.  I needed to do this in order to
get low latencies without xruns, but I think this also got rid of my
crackling entirely.

However I now think there were a few other things I could have tried
with the old VIA motherboard and just an unpatched kernel:
* Changing IRQs so that the sound card had a higher priority may have
helped (I used to try to get the sound card to have IRQ 9).  This can
sometimes (but rarely, it seems to me) be done in BIOS; the alternative
is to physically swap PCI cards around.
* Perhaps making some hardware buffer larger if that's possible (maybe
something can be done in asound.conf?)
* Changing 'pci_latency_timer' settings with 'setpci'.  This was
suggested in response to VIA-related problems, I did try it but with no
success.

I'm merely guessing with some of this, but hopefully it might help.

Regards,
-- 
Steven Chamberlain
steven at pyro.eu.org