The encoder chip used has this datasheet: http://www.holtek.com/pdf/consumer/2_12ev120.pdf
It looks like the module will transmit continuously, so if you can figure out the cycle
time through the 4 inputs you can ensure you don't change the inputs too quickly.
You'll have to build some sort of protocol on top of what the chip provides, its merely
an IR remote encoder/decoder pair with 4 input channels. Think of it as 4 slow
virtual wire connections.
More importantly though theses modules seem not to have the band/frequency
labelled, so cannot legally be operated until you determine what band they use and
whether that band is legal in your territory. Well I can't see that information in
the eBay link...