[hpsdr] Janus/Ozy with Linux?

[Frank Brickle]

Ramakrishnan Muthukrishnan wrote:

>> How hard would it be to integrate Janus/Ozy/Atlas into ALSA?  I note you
>> didn't mention that option.  I suspect that is the hardest way, but also
>> perhaps has some benefits for the labor.
> 
> I think there were afew suggestions on that on this list before. If I
> remember, we have an ALSA developer on the list. Perhaps it is quite
> possible.

There's a fundamental problem. Both audio and control paths lead through 
libusb. That means on Linux they're both in user space, since libusb is 
user-side code.

Unfortunately, ALSA drivers (the sound part of the configuration only) 
need to be loadable in the kernel.

Forget hacking ALSA. It's basically incompatible with this design. 
That's not to say there's no way to integrate OJ under Linux. The 
solution has to be somewhere at the user level, outside the kernel, however.

The immediately obvious strategy is to create a daemon talking to OJ via 
libusb, which splits and merges the control and audio streams and makes 
them available at the application side as file descriptors. That way 
ALSA can think it's MUXing to files for the audio data (using the file 
PCM plugins), and the hardware control functions can simply use ordinary 
IO for the control stream data.

73
Frank
AB2KT

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