Hi all
Thanks very much to Ragnar et al for help with this so far.
Update
We successfully set up high quality live audio streaming to a remote server, using darkice and the Wolfson soundcard. For anyone encountering the issues we had: we had persistent 'buffer overrun' reports from darkice, excessive CPU usage and crashes.
Buffer overruns were solved by 2 changes: overclocking the Pi to 950 kHz, and setting the darkice parameter 'realtime' to 'no' (default is 'yes'). We don't yet know the full implications of disabling realtime, but for us at present the results are good. The stream is 44100 Hz stereo with 16 bit depth at 256 kbps, vbr set to quality 1.0 (which is the maximum).
For those who may be interested, the changes above also permit very good quality live audio streaming in mono using the Icicle usb soundcard and an external XLR microphone.
We will have disk images available for both these approaches shortly.
Question about external microphones
We have been testing with the stereo microphones on the Wolfson board, and have been impressed by the clean sound and low self noise. This setup could be a great solution in some locations, but relatively few for our purposes.
We mainly want to stream live audio from locations outside, typically in wild places with sometimes harsh conditions. So for us it generally makes sense to have the Pi indoors and then to run cables outside to the microphone(s). We can do this with XLR microphones, but they are quite expensive, and we are looking to place many microphones at locations around the world, so the cost is a big issue.
We would like to take advantage of the Primo EM-172 electret condenser microphone capsules to make cheap, high quality stereo pairs for use with the Wolfson card.
For this we would need to access the Wolfson preamplifiers externally, perhaps via the expansion header pins. We would also need to provide 5V plug-in-power to the microphones. We would be very grateful if anybody has suggestions about how to go about that.
Thanks
Best wishes
Grant (soundCamp)