[LAU] Value of low-latency in audio?

david gnome at hawaii.rr.com
Wed Dec 23 02:46:32 EST 2009


Jonathan E. Brickman wrote:
> 
>> Just wondering. Without an RT kernel here, my 2 laptops seem to run my 
>> simple audio needs pretty well at 64msec latency. At least, it's never 
>> bothered my playing along with computer-generated audio.
>>
>> I don't do any heavy-duty audio work here. Once I tried Jackrack, put 
>> one effect in it (that worked) or one amplifer (that worked) but trying 
>> to use both didn't. But I don't know if that had so much to do with 
>> latency or lack of RT kernel as with a smallish amount of memory and an 
>> underpowered processor driving the whole thing. Now that I''ve upgraded 
>> the memory on both laptops, perhaps it would work? On musicbox, with 
>> 512MB, using a single good quality (larger) soundfont was enough to 
>> cause problems. With 768MB in it, it works without problems.
>>
>> I see people on the list running much lower latencies than 64msec, and 
>> seemingly trying to get even lower ...
>>
>> So, just wondering.
>>   
> Depends entirely on specifically what you're trying to do.  I'm using my 
> setup as a live-gig MIDI module, in the sense that when I play a note on 
> my keyboard, it sends noteon/noteoff via MIDI to the box, which either 
> (a) puts out that note as close to zero-latency as possible or (b) 
> delays everything, which hurts live cohesion in many ways, not the least 
> being my fellow band-members taking cues from the positions my fingers 
> are in. 

That's sort of what musicbox is headed for.

> It's true that RAM and CPU are both needed if you're going to use your 
> laptop for effects.  A good sound system can ease the CPU needs some, 
> but not much in the effects zone.  Apart from MIDI event processing, 
> soundfonts are actually perhaps the least resource-intensive 
> music-generation task in my current experience, as long as your sound 
> system is reasonably tweaked, except some simple sound synthesis tasks 
> in well-written code, e.g., some organ-only simulators.  Sophisticated 
> sound synthesis will eat your CPU alive (that's why I bought this AMD 
> X4), as will anything but the simplest effects setup.
> 
> Which brings me to a 'hmmm'.  CPU.  GPU?  :-)  Not yet, but we can pray 
> for it :-)

CPU in musicbox is a 2.8GHz Celeron processor. Not the Celeron M, the 
non-M version.

The "GPU" is old Intel 8xx series junk, and probably the source of about 
half of the xrum problems ... I tried a music distro on it that used 
KDE3 with Compiz, and having any of the video effects turn on would peg 
the CPU and bring sound processing to a silent halt.

-- 
David
gnome at hawaii.rr.com
authenticity, honesty, community



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