56 lines
1.9 KiB
C++
56 lines
1.9 KiB
C++
#ifndef MEDIAPIPE_FRAMEWORK_API2_STREAM_LOOPBACK_H_
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#define MEDIAPIPE_FRAMEWORK_API2_STREAM_LOOPBACK_H_
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#include <functional>
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#include <utility>
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#include "mediapipe/framework/api2/builder.h"
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#include "mediapipe/framework/api2/port.h"
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namespace mediapipe::api2::builder {
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// Returns a pair of two values:
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// - A stream with loopback data. Such stream, for each new packet in @tick
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// stream, provides a packet previously calculated within the graph.
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// - A function to define/set loopback data producing stream.
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// NOTE:
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// * function must be called and only once, otherwise graph validation will
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// fail.
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// * calling function after graph is destroyed results in undefined behavior
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//
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// The function wraps `PreviousLoopbackCalculator` into a convenience function
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// and allows graph input to be processed together with some previous output.
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//
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// -------
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//
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// Example:
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//
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// ```
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//
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// Graph graph;
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// Stream<...> tick = ...; // E.g. main input can surve as a tick.
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// auto [prev_data, set_loopback_fn] = GetLoopbackData<int>(tick, graph);
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// ...
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// Stream<int> data = ...;
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// set_loopback_fn(data);
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//
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// ```
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template <class DataT, class TickT>
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std::pair<Stream<DataT>, std::function<void(Stream<DataT>)>> GetLoopbackData(
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Stream<TickT> tick, mediapipe::api2::builder::Graph& graph) {
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auto& prev = graph.AddNode("PreviousLoopbackCalculator");
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tick.ConnectTo(prev.In("MAIN"));
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return {prev.Out("PREV_LOOP").template Cast<DataT>(),
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[prev_ptr = &prev](Stream<DataT> data) {
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// TODO: input stream info must be specified, but
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// builder api doesn't support it at the moment. As a workaround,
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// input stream info is added by GraphBuilder as a graph building
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// post processing step.
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data.ConnectTo(prev_ptr->In("LOOP"));
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}};
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}
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} // namespace mediapipe::api2::builder
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#endif // MEDIAPIPE_FRAMEWORK_API2_STREAM_LOOPBACK_H_
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