I just did an IR remote using RC5, and I had to sort this out. I did it using an SiLabs C8051F226, which only has the standard 8051 INT0\ and INT1\ falling-edge interrupts. I found it easiest to simply interrupt on the IR receiver module's first start bit falling edge, then disable the external interrupt and use a timer to count to the middle of each bit (well, not the transition in the middle, but the middle of bit time before or after the transition ... pick one).

Another way to do it would be to use a device with more-flexible external interrupts. Other SiLabs parts let you interrupt on any transition on a port pin. A simple state machine would keep track of the current state of the bit, and the interrupt could process whether the transition meant the new bit is a zero or a one.

A third way to do it is to simply poll for transitions and again use a simple state machine to determine the value of each incoming bit.

There are lots of ways to skin this cat.

-a