Hi, On Tuesday 24 March 2009 13:18:37 Frank Barknecht wrote: > Arnold Krille hat gesagt: // Arnold Krille wrote: > > I _seriously_ doubt that all usb devices have the same latency. Indeed > > they do alls have the same latency introduced from the usb-protocol added > > to their specific latency, but that specific latency still depends on the > > actual hardware and the driver. And yes, there are different usb-audio > > drivers in the linux kernel, just search for *usx2y* for example. And the > > hardware latency is determined by the converters and the processing chip, > > just like with any other sound device, be it pci, pcmcia or firewire > > based... > I'm no expert on this, but IMO ALSA-dev Clemens Ladisch is one. He wrote: > "Due to how the USB protocol works, all USB audio devices have the same > latency." I know that clemens knows his stuff. But he is talking about the usb-protocol here. The same can be said about the firewire interfaces: Because of the way firewire works all have the same latency[*]. But still that is the latency of the bus/transport. You have to add the latency of the actual hardware and I am very certain that there are different converters/chips in use in the different usb audio devices. And even with using the same chips, the programming in the firmware can be different resulting in different latencies. [*] Probably this statement is not as true for firewire as it is for usb as firewire seems to allow synchronuous and asynchronuous transfer, so its probably two different protocol-specific latencies in the fw-world. But for the details you have to ask ppalmers or wagi or Jonathan Woithe who all know more about firewire than me. I just know from actually programming (or at least trying to program) an atmega with an ad-converter connected by a bus that inside the device you have an additional latency, no matter which device. Arnold
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