A useful tip is that if you have a cheap computer speaker you can place it close to the transmitter — when it transmits, the speak often picks up the signal and you can hear some sort of beeping sound. Probably not all speakers will pick up the signals, so try your remote control first and see if the speaker can pick it up. Then try OSPi. If there is no actual signal sent out from OSPi, you should check if +5V and GND are wired to the transmitter correctly. Also, after you modified the source code, and recompiled, you should restart RPi to effect the changes.
The computer speaker trick can also allow you to identify if the simulated signal roughly matches the original signal. Specifically, the pitch you hear is correlated with the signal timing — the slower the signal, the lower pitch you will hear.