Support
Looper's Delight
|
Support |
|
|
Very cool! Thanks for that technical discussion, I love learning about that. And I certainly can't argue technical details, I don't know enough about them. But I know more now. But I can honestly state my experience, which is, and remains: On the same system, same settings, same software: latency is different between the m-audio I used and the motu. It could very well be the way the drivers are written, but whatever the reason. It was noticeable in my system. > So, this was a long winded way of saying that it is difficult to > make generalizations like "the MOTU has lower latency than the > M-Audio". But it is ok to make generalizations that firewire devices are the same, in terms of latency? Technically, after your report, yes. Based on my experience, no. But I wasn't trying to make a generalization about all fw devices, I was answering a question using a comparison between devices based purely on my experience, and will try to be more clear in the future that it is purely my opinion/experience. So also, my apologies if someone felt maligned by my language if I seemed to be slamming someone's beloved device. Anyway, this is a long winded way of saying I may be technically incorrect, but I stand by my experience.....but from now on I will say, "I couldn't tune the latency low enough...." And, really, thanks Jeff, for all that great information. It helps to discuss from a more technical standpoint. best regards, Jeff Jeff Kaiser http://www.jeffkaisermusic.com pfMENTUM.com • AngryVegan.com On Jun 7, 2006, at 9:25 AM, jeff larson wrote: >> From: Jeff Kaiser [mailto:loopersdelight@pfmentum.com] >> >> I created my live rig in Max/MSP. I don't know how to measure >> latency, so I can only say I don't notice it after switching to the > MOTU > > Technically it is incorrect to say that one audio interface has better > latency than another. Latency in a computer-based system isn't a fixed > characteristic of a device, it is something you tune for the > combination > of components in your system including the audio interface, computer, > operating system, other attached devices, and many other tings. > > At a simplistic level, you can think of latency as being defined by > two things: the size of the buffer used by the software device driver > and the size of the buffer used by the hardware digital/audio > converter in the interface. You have no control over the DAC buffer > size, but you do have control over the driver buffer size. > > So assuming that two devices have comparable DAC buffer sizes, > and you set the driver buffers to be the same, the two devices > will have exactly the same amount of latency. One cannot be better > than another. > > "But wait!" I can hear some of you say. What about those DAC buffers? > If one device has a smaller buffer then it has better latency right? > Technically yes, but we're talking about extremely small buffers, > somewhere between 5 and 100 samples. Measurements of my sound card > indicate that it has a buffer of around 32 samples. I don't care how > sensitive a musician you think you are, *you cannot hear this*. > > Think you can? 32 samples at 44K is about 0.64 milliseconds. The > speed of sound is 13.63 inches/millisecond at 75 degrees F. So a 32 > sample buffer produces the same amount of delay as moving your head > about 8.7 inches away from a sound source. The difference between > slouching over your acoustic guitar vs. sitting upright. > > So unless the audio interface's DAC has an extraordinarily large > buffer, latency is determined by the device driver buffer. As I said > before you get to decide what this is. You tune latency by setting > the buffer size as low as possible without hearing artifacts that > usually sound like clicks. How small you can set this buffer is > determined by a lot of things. One of them is the quality of the > device driver for the audio interface. > > If one device has a badly written driver that does not allow you to > select small buffer sizes without hearing clicks, then you could say > that the device "has higher latency" than another but what that > really means is "I cannot tune latency low enough". > > In my limited experience with "prosumer" grade audio interfaces, the > the device driver has never had any effect on latency. Latency > problems I've had have always been related to the other things running > on the computer, and the other devices attached to it. > > So, this was a long winded way of saying that it is difficult to > make generalizations like "the MOTU has lower latency than the > M-Audio". > The latency you can achieve is dependent on many things in the system, > it is rarely an intrinsic characteristic of a single device. > > Jeff >