Using Streaming Algorithms that Require matrix_real

[nvssynthesis]

I am wondering how to use any of the streaming algorithms that require a matrix_real as one of their inputs or outputs.
For example, the Onsets algorithm expects a matrix_real, which is a typedef for TNT::Array2D, as the "detections" input.
Normally, if it were e.g. a Vector input, I could use essentia::streaming::VectorInput to get it working in a streaming Network, but I am at a loss as how to do something similar with a matrix_real.