Decode an infrared signal with an IR demodulator inside a microphone jack
Yes you can plug it in the microphone jack with a few extra components.

Here what schematic I have found on LIRC's webpage (by Matthias Ringwald):



As far as I know most IR signals are Manchester coded:


high to low transition means 1
low to high transition means 0


Or the other way round because there are two conventions.

Be sure to check SB-Projects for information regarding different IR protocols.

To view the signal on your PC I recommend Christian Zeitnitz's Scope and to record it try Audacity.