I need to be able to transfer data from a loudspeaker to a microphone by inserting a small data payload into the audio signal that the speaker plays. When the microphone captures the audio signal, an application must be able to extract the data payload from the recorded audio signal.
The inserted data must be inaudible to the human ear
Source code has to be cross-platform
so only use standard C++
Do not use pre-compiled (third party) libraries
if you use any libraries they have to be included as source code!