Graph

A flow graph is constructed and run using the graph class. First create an instance

flow::graph gr;

Adding filters

Filter nodes are added using

my_filter& filt = gr.add_filter<my_filter>(...);

If the filter’s constructor takes additional arguments (after the first filter_node&), they can be passed to graph::add_filter and will be forwarded to it. The function returns a reference to the created filter object. The filter object, and the underlying node, are owned by the graph, and will be destructed when the graph is destructed.

This creates a synchronous node by default. To create an asynchronous node for the same filter, use

my_filter& filt = gr.add_filter<my_filter, flow::async_node>(...);

To create the sink node, use

my_sink_filter& sink = gr.add_sink<my_sink_filter>(...);

Exactly one sink must be created for the graph.

Connections

Connections are made using the connect() function of filter inputs:

sink.input.connect(filt.output);

Here, sink.input and filt.output need to have the same frame dimension and element type. Connections must be made before the graph gets setup.

Currently, all inputs of all filters that were added into the graph need to be connected. Connections are one-by-one, it is not possible to connect multiple inputs to one same output.

Running graph

After the connections have been made, the graph needs to be setup using

gr.setup();

This initialized the underlying nodes, allocates buffers and creates threads, and calls the setup() functions of the filters.

After that the graph can be run using

gr.run();

This runs until the end of the stream. Alternately gr.run_for(time_unit duration) and gr.run_until(time_unit last) can be used to run only for a limited number of frames.

The graph is seekable if all its source filters are seekable. When this is the case, the time index can be changed using gr.seek(time_unit pos).