Reverse engineering modulated audio data

[holozip]

Hi folks,

I have an OSD unit onboard a model aircraft, which monitors battery life, speed, heading, altitude etc - and then overlays the results on top of a live video feed. It also modulates a data stream onto the audio channel, making the data available to accessories such as antenna trackers, or an iPhone app that plots the location on a map.

I'd like to reverse engineer the audio and use the data stream for use in my own projects, but I know very little about how to identify the encoding scheme.

Here is an example of the audio I found on youtube:


I've tried running the audio through the various modes available in sdr-radio without any success.

Can anyone help point me in the right direction?

[philpem]

It's probably something simple like FSK or 2PSK, but you'd need an uncompressed sample of the audio to confirm that. Trying to work from the compressed audio in a Youtube video would be a fairly difficult feat...