BMediaEventLooper

The BMediaEventLooper class provides a control thread that automatically queues received media events and calls the HandleEvent() function you implement to process them as necessary. This takes a lot of the drudgery out of writing nodes:

• You don’t have to write a service thread to receive and process incoming messages; BMediaEventLooper does this for you (much like a BLooper, hence the similarity in names).

• You don’t have to write code to queue up events until it’s time to handle them, since BMediaEventLooper maintains a BTimedEventQueue for you. Just push events onto the queue as you receive them and the BMediaEventLooper pops them off for you at the appropriate times and asks you to handle them.

• If all your node needs to do is know when Start(), Stop(), and Seek() requests come due, your node doesn’t even have to override these functions—BMediaEventLooper automatically intercepts them and pushes them onto the queue for you.

• The BTimedEventQueue employed by BMediaEventLooper automatically provides support for queueing multiple start, stop, and seek events.

BMediaEventLooper maintains two queues: one for real-time events, and one for normal events. Events in the real-time queue are handled according to their real time, while events in the other queue are handled based on their performance time. So the values of the time stamps on events in these two queues are handled differently; keep this in mind if you need to peek into the queues yourself.

Implementing a Node (the Easy Way)

Although BMediaEventLooper does take away a lot of the complicated node construction work, there’s still work to be done. There are still plenty of hooks you have to implement yourself (which ones, exactly, depend on whether you’re a producer or a consumer).

You can study a specific example of how to implement a node using BMediaEventLooper by reading “A BMediaEventLooper Example”.