we will :-) Markus's stuff is fine but we've actually got 90% of the driver and I was curious to know before doing the last 10%. ----- Original Message ----- From: Jerry J. Trantow To: wdmaudiodev@xxxxxxxxxxxxx Sent: Monday, April 19, 2004 4:26 PM Subject: [wdmaudiodev] Re: Where is the latency in the USB audio stack ? Why not go asio? I've worked with Markus Medau at http://www.usb-audio.com/ He provides very low latency asio usb drivers for the Sound Device USBPre as well as other products. His driver was designed for asio but also functions as a Windows audio device. -----Original Message----- From: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Jerry Evans Sent: Monday, April 19, 2004 10:14 AM To: wdmaudiodev@xxxxxxxxxxxxx Subject: [wdmaudiodev] Where is the latency in the USB audio stack ? Hi all. We have some custom input only hardware running over USB 1 at 6 * 16 * 48K. Most happily the stock WinXP SP1 USB audio driver works properly when accessed in KS mode from our own user-mode app(s). The downside of this arrangement is that we need to sync 2 KS devices to enable low-latency playback. Measurements indicate that having 2 USB devices plugged into a single USB 2 hub (theoretically optimal configuration) gives us a minimum practical latency of ~45 ms. This leads me onto the core issue: Given that there is at least 10ms latency in the USB audio stack (as posted by DJS sometime last year in this list) we were wondering if a suitable USB driver could be made to supplant the stock USB stack, i.e. the user could opt to install the high performance driver. Question is how much of a win we might get: is the latency all in usbaudio.sys or is it further down the stack ? We'd be most happy if we could get the overall latency down below 20ms. Any tips would be greatly appreciated.