[Ardour-users] WAV files, xruns

[Anthony DiSante]

Jesse Chappell wrote:
>  > > Also, how do I know what values to choose for -n and -p for my card?
>  > 
>  > OK, I can't set n to anything but 2.  However, I set p to 4096, and now 
>  > there's no more xruns (so far)!  Thanks a lot.
>  > 
>  > How can I test the actual value of latency on my system?
>  
> As usual, terminology may be confusing here.  Latency is a fixed
> measurable buffering delay defined entirely by your period size
> (4096 here), the period count (2) and your sample rate.  
> 
> What you want to know, is how small of a latency can your system
> handle your system without buffer over/underruns.... and it appears that
> that number is not very small on you system, sadly.  
> 
> Did you say what audio hardware you are using?

OK, it looks like the lowest period I can use without xruns is 2048.  So I'm 
doing:

jackd --realtime -d alsa -d snd-emu10k1 -n 2 -p 2048

And then I get:

creating alsa driver ... 
snd-emu10k1|snd-emu10k1|2048|2|48000|0|0|nomon|swmeter|rt|32bit
configuring for 48000Hz, period = 2048 frames, buffer = 2 periods
Couldn't open snd-emu10k1 for 32bit samples trying 24bit instead
Couldn't open snd-emu10k1 for 24bit samples trying 16bit instead
Couldn't open snd-emu10k1 for 32bit samples trying 24bit instead
Couldn't open snd-emu10k1 for 24bit samples trying 16bit instead

And then despite those 4 warnings/errors, it works fine, I guess at 16 bit.

(My hardware is an SB Audigy 2-channel consumer card.)

So can I tell what latency I've achieved based on those numbers?  I've seen 
people on this list say, "I get X ms latency," etc.  Is there a formula?  I 
assume it's something divided by the sample rate (in kHz) in order to get a 
result in ms.

-Anthony
http://nodivisions.com/