Re: [Discuss-gnuradio] Re: FUNCube dongle

[Moeller]

On 26.02.2011 11:36, Patrick Strasser wrote:
> Just putting USB Audio Class 1 on USB 2.0 would not work, because blocks
> are structured different between 1.1 and 2.0.

That was my hope, but I didn't check the specs if it would be possible.

> But back in 2005 USB Audio Class 2 (UAC2) was adopted, offering notably
> higher sampling rates and bit depths. Apple introduced a UAC2 in Mac OSX
..
> The SDR widget people sounded every possible combination for the
> mentioned OSes, with lots of tricks to get the very best out of every
> driver (especially Windows UAC1). They have different firmware for UAC1
> and UAC2.

UAC2 with USB3 would be a good combination. With the "usb3" "uac2"
keywords in Google you find some developments for a "USB Super Speed patch"
in USB3 audio drivers. I think it's realistic because UAC2 is supported
in Linux and USB3 is now common in modern PC. With about 5 Gbit/s
it allows broadband SDR solutions, hopefully also low-cost ones.

> You can set every integer sampling rate you like withing the capacity
> limit, but most drivers expect the common sampling rates. The drivers
> are the limiting factor.

At least in Linux you can tune the drivers if you want.

> And still synchronization of clocks is a big problem.

Sync problems? I thought, the "audio" devices implement
a fixed sampling clock and the USB transmission is buffered to
achieve a continuous stream without gaps or clock variations.
Only the PC audio output has a different clock, but that problem
occurs with other external sources too, like the USRPs.