The sync header at the start of the message is intended to gives you a bit time expectation; measure a few and average them.

The idea here is time the bits and then set up your timer so that you offset a HALF bit. This means that if you now sample at the bit rate, you'll be sampling during the clean CENTER of the bit cell far from the bit edges. Due to the short block size, this is usually sufficient.

This is not good for larger data transmissions because the error in timing can quickly get you bit samples out of synchronization. But IR Remotes are designed to be cheap. Their oscillators vary too much and so the receiver should use the sync information available to read them.

aka j