OutputBackend

The output half of a platform: one clock, one audio sink factory, and optionally a subtitle rasterizer. It supplies no video renderer: a renderer needs a surface that only the application owns, so the application builds one and passes it to KitePlayer.attachRenderer.

The clock and the sink travel together because they cannot be chosen independently. An audio sink reports when a buffer becomes audible on the platform's own time base, and the engine anchors its master clock to that instant. Measure time from a different source and the two agree only by luck: audio and video then sit at a constant offset that no correction can find, because both sides believe they are right. The Apple sink asserts the pairing at construction, and this interface is what stops the mismatch from being assemblable in the first place.

There is no discovery here either. A platform provides one object that wires its own pair together, and whoever creates the player passes it in.