Bug 96804

This is the only documentation about `module-filter-heuristics` and `module-filter-apply`:

### Modules to allow autoloading of filters (such as echo cancellation)
### on demand. module-filter-heuristics tries to determine what filters
### make sense, and module-filter-apply does the heavy-lifting of
### loading modules and rerouting streams.

By reading these lines, I still have no idea what these filters actually do, and why both are required to operate.

That's not enough for me, I want to know /exactly/ what these filters do. I can read the code, but I shouldn't have to. If you look online, the first thing everybody suggests is to disable these modules as nobody knows what they are supposed to do and in which conditions.

Please document the exact behavior.
Thanks.