[wdmaudiodev] Re: KMDF for a USB audio driver?

  • From: "Jerry Evans" <jerry@xxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Fri, 3 Mar 2006 18:07:30 -0000

Nick,

You will be hard pressed to get <10ms roundtrip via DirectKS with decent PCI card.
You will not even get close with DirectKS and USB hardware as there is 10ms of buffering in the stack.
With a decent custom driver you should be able to get single figure roundtrip latencies over USB.


That said: I've no idea of your resources but there are already solutions out there that may be more cost effective than a complete DIY approach. Writing a driver that will work with all USB audio class compliant hardware (which it should!) is not a trivial undertaking. I suspect that the core of the driver, setup, teardown and handling isoch packets, is about 10% of the task, with the rest being a vast amount of testing of installations and hardware targets.

See www.usbaudio.com and http://www.thesycon.de/eng/home.shtml for more info on alternatives. I have no connection with either of these organisations save for once buying a retail driver from the USB audio guys.

HTH

Jerry.

----- Original Message ----- From: "Nick Dowell" <nick@xxxxxxxxxxxxx>
To: <wdmaudiodev@xxxxxxxxxxxxx>
Sent: Friday, March 03, 2006 5:34 PM
Subject: [wdmaudiodev] Re: KMDF for a USB audio driver?



I get the impression you don't have much of an idea how software music production applications get used, so I don't think you're qualified to speak for those of us working in this field.

On 3 Mar 2006, at 17:07, Tim Roberts wrote:

Why?  I mean, was this "10 ms" number a bullet point on a PowerPoint
slide concocted by some marketing guy after a bottle of cheap bourbon,
or do you actually have some empirical usability studies that show
complaints if latency is higher than that?

Studies have shown that hearing your own signal monitored more than 10 ms later seriously affects performer's abilities to keep in time.


http://ccrma.stanford.edu/~grace/chafeISMA.pdf

In a recording scenario one often listens to the already recorded tracks combined with their live signal with effects applied. This requires the signal to be processed by the application, and therefore go in and out of the driver.

Low latency is also very important when playing virtual software instruments. Most musicians complain when the delay between pressing a key and hearing the sound reaches over 10 ms latency, and again have trouble keeping in time or playing fast.

There's a reason why this figure of 10 ms gets used so often, and it isn't down to some marketing bozo.

I guess what I'm saying is that I don't believe you.  Most telephones
have vastly more than 10 ms latency.  Most cell phones have many
hundreds of  milliseconds of latency, and people are fine with  them.  50
ms latency in a movie or TV show is undetectable.

Um, I'm not sure what your point is here. Every application has different requirements, and how often do you think musicians play together over a teleconferencing system?


If you really need sub 10 ms latency, then you need a piece of  hardware,
not a general purpose computer running a consumer operating system.

Tell that to everyone out there using Cubase, Sonar, Logic etc...

Many soundcards on Windows with custom driver offer throughput latencies of 5-10ms (just look at M-Audio, RME, MOTU, Echo...). Oh and this product on Mac OS X offers about 7ms thru latency without breaking a sweat.

Nick
******************

WDMAUDIODEV addresses:
Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx
Subscribe:    mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe
Unsubscribe:  mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe
Moderator:    mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx

URL to WDMAUDIODEV page:
http://www.wdmaudiodev.com/


******************

WDMAUDIODEV addresses:
Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx
Subscribe:    mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe
Unsubscribe:  mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe
Moderator:    mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx

URL to WDMAUDIODEV page:
http://www.wdmaudiodev.com/

Other related posts: