I apologise in advance for asking here, but extensive enquiries turn up absolutely nothing.
There are three ways to potentially do it:
1) 3.5mm jack
I can plug in the hands free kit, and the mike on that works with the Sound Recorder app. However, the video camera app continues to use the built-in mike in this case.
I have tried several USB sound interfaces and none work at all. One drew 60mA and another drew 120mA, and I also tried it powering both externally (breaking into the +5V USB rail so the phone doesn't have to supply any +5V). Nothing works at all. In just one case, the phone said the device was incompatible.
Obviously, the phone doesn't dynamically load USB drivers from nokia.com like a PC might. Is there a document somewhere describing which USB slave chips (which USB "sound cards") the 808 is hard coded for?
I cannot find any bluetooth product which has an external sound input.
There is no config in the phone for anything that I can find.
From some random one-line remarks on the web, it appears that many people have been up this road before. Nobody I can find managed to get USB or bluetooth external audio to work in ANY mode, and some got the 3.5mm jack input to work but not for the video camera.
Is there a document somewhere which details how this is all supposed to work?
The Nokia community forums are, of course, useless.
Very many thanks in advance for any pointers.
UPDATE: the 3rd party camera app, CameraPro, does use the 3.5mm jack for audio on videos. So the problem is with the Nokia camera app. The USB issue remains.