I've done exactly what you're asking before. Each manufacturer has different means of encoding the data. There is a wealth of information on the web. I wrote my code to output a particular manufacturer's code (NEC).

If you want a quick and easy solution - buy a learning remote and connect relays contacts across the pushbuttons in the learner remote. Have your controller activate the relays. There are other ways of doing it apart from relays, but relays are simple to begin with.

There is some code on the dunfield development systems website that allows you to read an IR signal and to replay it using a 8051.

The learner remotes normally have a bit of battery backed ram to store the recordings - you will need this also if you want your micro to record also.