Expanding on what Hexreader wrote:
IR signaling protocols broadly fall into three categories
1. Constant mark duration with the space duration varied to represent 1 or 0,
2. Constant space duration with the mark duration varied to represent 1 or 0,
3. Constant bit rate with the inversion time used to represent 1 or 0. (RC5 and RC6 protocols)
Here, 'mark' means the carrier is enabled and 'space' means the carrier is disabled. The carrier is typically in the range 35 to 45 KHz. The actual durations vary from one product to another and usually, but not always, the data is split into an address field (to select one particular product) and a data field (to select the function on that product). Also many products send the ID data burst twice, once in 'normal' form and then with the original address and data bits (but not the mark/space timing) inverted.
If you want to send audio or video directly via IR, there is no established protocol and it is actually quite difficult to do, especially at video (up to ~5MHz) rates. For audio, most systems use multiple carriers, all FM at frequencies just above the audible frequency range.
Brian.