[LAU] jdelay - measured latency of a usb interface

torbenh at gmx.de torbenh at gmx.de
Tue Mar 24 09:07:08 EDT 2009

On Tue, Mar 24, 2009 at 01:18:37PM +0100, Frank Barknecht wrote:
> Hallo,
> 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...
> > 
> > Have fun and excuse my nitpicking,
> 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." 
>   http://lalists.stanford.edu/lau/2005/06/0200.html

that statement is 4 years old.
i doubt it holds. because the statement that USB cards require -n3
doesnt really hold anymore. so a lot of stuff changed.
well... i am getting a few xruns with -p128 -n2 but this is nowhere near
the xrun storms which were hapenning with 2.6.26....

torben Hohn
http://galan.sourceforge.net -- The graphical Audio language

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