Control signal from headphone jack?

I have a situation where I'm trying to send a control signal (via the analogue inputs) to the arduino from the headphone output of a bluetooth audio receiver (roughly the same kind of output as an ipod). The signal is weak and noisy so I am experimenting with amplifying it to use more of input range of the arduino.

Which will be a better way of smoothing out the data? a physical envelope following circuit? Or trying to smooth (average) the data in the code? I can not send a control voltage over bluetooth because the audio receiver filters DC out of the audio. So I'm going to need to implement some envelope following somewhere. Any suggestions for a very simple amplifier/enveloping circuit?

Thanks,
Casey

I think your problem is not a weak and noisy output signal only. Perhaps it's a question of matching impedances.