Input and resampling

The input operator is just an operator that is designed to be a good intake of the external signal. Programs must have at least an input operator, which will perform sanity checks on the input signal before forwarding the message to others. For example, an input operator will discard new messages with timestamps prior or equal to the last message received, guaranteeing the time order in the messages it forwards.

Resampling

Many operator implementations assume that the messages they will receive are time ordered and equidistant in time, or equally spaced in time. We will call this type of signal a regular one, while those that don't fulfill this will be named irregular. This is a strong assumption and it will likely be the case that input signals are irregular. This is why we have a special set of operators called resamplers.

A resampler operator will take an irregular input signal and will produce a regular one. Internally, it will use the irregular signal as its source of truth, to find a realistic interpolation over the time grid points. The interpolation algorithm depends on the resampler used. In practice this means that, while not strictly necessary, programs will start with input operators followed by resampler ones.