Android Question External Microphone?

[Michael Gasperi]

Would you think that a phone would automatically switch the microphone input from the built-in one to the mic in a headset/mic plugged into the 3.5mm jack? I'm using the audio.streamer for sound input and output and I'm afraid that under some conditions the mic source won't automatically switch just because you plugged in an external mic.

 

[stevel05]

I haven't been able to find an option to switch on an external microphone, so I would think it should be automatic. Do you know under which conditions if fails?

 

[Michael Gasperi]

Thanks for getting back to me.

I'm measuring electrical resistance by using the 3.5mm jack normally where you plug in a mic/headset. I output a 100Hz signal on the left channel. The signal flows through the resistor back into the microphone input. Basically the louder the mic signal the lower the resistance. I know it sounds pretty odd, but it works to measure skin resistance which is used for biofeedback and lie detectors. If you want to see more details you can look at http://www.extremenxt.com/gsr.htm

Anyway, this works on a Nexus 5 and an old cheap smart phone I've got, but it worries me that some phones don't use the external mic just because you plugged something into that jack. Or maybe the audio channel should be something other than Volume_Music. I've had a user of the App tell me they don't seem to be getting any mic input and thought maybe something like this was the problem.

 

[stevel05]

That's an interesting experiment. Having looked at some posts on Google I can't find anything definitive, but needless to say that it is possible that some devices just don't support an external microphone, and some that should, don't work properly. Do you know what device the user was trying it on?

 

[Michael Gasperi]

Droid Razr Maxx HD

 

[stevel05]

Seems like there might be an issue, but I don't know if this qualifies: https://motorola-global-portal.cust...er_detail/a_id/95459/p/30,6720,8882/kw/square

last paragraph.

 

[Michael Gasperi]

Wow! Nice find.

Kind of an odd statement about "microphone input but no microphone output". However, I think the square card reader works by doing something like I'm doing. Putting out a signal on the earphone output and inputting a signal on the mic.

Any idea what constitutes a "microphone output"?

 

[stevel05]

No unfortunately not, I wondered about that too.

 

[Michael Gasperi]

The help topic also says the phone doesn't work with the Jawbone UP which apparently communicates by plugging into the audio jack.

http://eftm.com.au/2013/04/the-jawbone-up-wellbeing-is-a-state-of-mind-10408

I perused the Square and Jawbone support pages to see if they list other incompatible devices. Fortunately the list doesn't look too long.

Thanks again.

 

[Michael Gasperi]

Just in case anyone still cares about this subject. I found some hacking information on the Square. http://andybromberg.com/credit-cards/ Turns out it ONLY uses the microphone input so the Motorola problem may be with Apps that use the external microphone but don't set up anything for output. It is not clear if the Jawbone UP device only sends data to the phone and not some bidirectional communications. If it is one way, then that would be the same problem.