Lower Latency with USB than with Firewire; how??

[dn83]

Hi all --

I have been using firewire audio interfaces with both PCs and Macs for a few years now. I had tried USB ones, but as we all know, they have higher latencies than firewire.

I was recently troubleshooting an issue and in doing so, picked up a cheap USB audio interface - the M-Audio MobilePre (second generation).

I have been unable to confirm if it is USB 2.0, but the strange thing is, I'm getting lower latency with it than with my firewire interface (the PreSonus FireStudio Mobile)...how can this be??

The difference is pretty substantial; the best I can safely get with the firewire interface is about 512 (25 to 30 milliseconds overall latency)...with the M-Audio MobilePre USB, I'm getting 128 (10 milliseconds overall latency), even when tested with a heavy Live 7 set...?!

Does anyone have any insight into how this could be? I'm interested to hear your thoughts. Thanks!

[shuutobi]

Drivers.

[dn83]

Ah yes...I was suspecting that. =)

[Tone Deft]

as we all know, they have higher latencies than firewire.

*cough*bullshit*cough*

they're pretty much the same. only reasonable argument I've ever read is that when you're doing many many many many audio channels firewire is better and that was a marginal argument at best.

or post a credible link and teach me something.

[Khazul]

All things being equal, then generally the lowest acheivable *reliable* latency between FW and USB2 should be about the same, but with FW requiring more CPU and leaving a little bit less for you audio application.

Now in practice, as the RME UFX is the only dual interface (ie it has USB2 and FW400) audio interface that I know of, then you might be hard pressed to test this in any meaningful way due to hardware and driver differences between differen companies and interface models etc, but my breifs est with the UFX tend to back that up.

In theory, USB2 can acheive lower latency (than FW400), but tends not to achive it relaibly due to drivers, other stuff thats connected to same root hub, which port the audio interface is conncted to, other stuff running on the machine... etc etc. FW is usually just safer, even with its generally higher CPU use to do the same amount of work. And if you running some dodgy motherboard chipset set, then all bets may be off anyway. In practice FW tends to be better under heavier load due to way it manages bandwidth use etc.

Also it could be that your FW audio interface just hates the FW chipset in your computer - that used to be quite a common problem.

[Tone Deft]

^interesting.

I imagine in the day and age of multi-core computers the marks against FW for being a CPU hog become less important.

[Khazul]

In this day of high speed multi-core computers Ive also noticed that good USB2 audio interfaces have become very reliable these days

A few years agao - I wouldnt touch USB2 for audio with a barge pole - now its what I use all the time with the exception of my UFX being connected to my PC via FW (so tha mac can connect to it at the same time via USB2).

The headache with USB is it isnt obvious whether the port is being shared or not until you actually plug something into them all and look at you system diagnostics to see what devices are on what ports and which are sharing hubs etc - basically like the old irq conflict nightmare from the old days back to haunt us. Now generally with FW, you dont tend to get a load internal devices hanging off firewire.

[gosinisha]

rme devices, for example use usb hardware and bypass the class compliant composite driver, and use their own. otherwise, forget 4ms or less.

[crumhorn]

I have a presonus firepod, but I guess the drivers might be similar.

with the firepod If you right click on the presonus tool tray icon you get a little menu with a CPU setting - make sure it is set to "high". It makes a huge difference.

Also for all the slagging off people give to M-Audio their drivers are very fast. I've never quite managed to match the latency since I replaced my fw410 with the firepod.

[dn83]

Interesting, thanks...I didn't know about the FirePod CPU tool, very cool...the control panels for the Inspire and FireStudio Mobile do not have this to my knowledge.

Right...I had tried USB interfaces in the past, but I get the feeling that until recently, they were not quite on par with FireWire.

Also...I have had my fair share of experience with USB chipset problems (interruptions in the audio stream, drop-outs, crackles, no matter how high you set the latency)...it seems that the only manufacturers currently using decent chipsets for USB (and FireWire for that matter) are ASUS and SONY. I own an ASUS myself.

Looking forward to seeing the first Thunderbolt / ("Light Peak") interfaces!!

[gosinisha]

intel ich8/ich9/ich10 and nec usb3 work perfect. some asus usb controllers have been reported uncompatible by rme.

[Simbosan]

The only issue I have had with USB is bandwidth. The USB soundcard I have reserves 40% of the USB bandwidth, my wind controller wants 20%, all good till I plugged in a Webcam and my EWI stopped working... Turns out that the webcam wanted 60% reserved...

That was the only issue I have had with USB, no webcam for me!

S