I want to be able to set keyframeable attributes on a clip. These attributes then affect the output of a transmitter or a player.
My idea of how to do this is to create a filter that has the attributes I need, but doesn't actually alter the pixels. Instead it just stores the attributes somehow (in the PPix?). Then the transmitter/player will read the values of these attributes and modify its output. The question is whether it's possible to store data about the frame inside a filter, and read it from a transmitter/player.
I guess I could create my own pixel format that contains the data, but that seems a bit overkill, and inconvenient.
You could achieve this by looking for the existence of the effect in the segment at the current timeline position, and then getting the effect parameter data. In your transmitter, you'd use the Video Segment Suite, much like the RTPlayback sample uses the suite to parse the timeline, and you would search for an effect node with attributes matching the effect you're building.