What is an event filter? It is a mechanism to filter songs before adding them to the playlist. Why is it any useful? To implement something better than a priority system!
Real world example: you have many events. Some are very long (“shows”), some are short (“jingle”). If you have a long show of 2hours, and a jingle every 15minutes, then at the end of your jingle you’ll find 8 jingle stacked. That’s bad! How to fix it? There are many solutions, none of them is very general or suits every need. EventFilter is a mechanism to have multiple filters running serially to find a reason to exclude an event.
Using an event filter¶
larigira provides some basic filter. A simple example can be “maxwait”. The principle is just “don’t add new events if the current playing song still needs more than X seconds to finish”. Setting this to, for example, 15 minutes, would have found only one jingle in the previous example. Great job!
However, it wouldn’t be very kind of long shows. If you have two long shows, each 2h long, scheduled let’s say at 8:00 and 9:30. Now the second show won’t start, because there is 30min remaining, and the maxwait is set to 15min. If you have this solution, maybe percentwait will better suit your needs. Set this to 200%, and a jingle can wait up to twice its own duration. This is like setting maxtime=4hours for the long shows, but maxtime=1minute for jingles. Nice!
This snippet will configure larigira to wait a maximum of 5 minutes:
(60*5 = 300seconds). This will basically cancel any event that finds a currently playing audio not at its end. It can be recommended if you have very accurate timing or don’t care about “losing” shows because the one preceding it lasted for too long.
This will configure larigira so that a 1-minute jingle can wait for a maximum of 4minutes, while a 20minutes event can wait up to 1h20min:
400 means 400%, that is 4 times the lenght of what we’re adding
Write your own¶
You probably have some very strange usecase here. Things to decide based on your custom naming convention, time of the day, moon phase, whatever. So you can and should write your own eventfilter. It often boils down to very simple python functions and configuration of an entrypoint for the larigira.eventfilter entrypoint.