Merge pull request #20546 from sivanov-work:initial_vpl_source

G-API: oneVPL (simplification) source base commit

* oneVPL source initial

* Fix compilation

* Fix compilation path

* Fix NO VPL compile

* Fix unused vars

* Fix unused vars in example

* Simplify oneVPL search: no custom path & download

* Fix standalone GAPI

* Apply comments

modules/gapi/include/opencv2/gapi/streaming/onevpl/onevpl_source.hpp

@@ -0,0 +1,44 @@
+// This file is part of OpenCV project.
+// It is subject to the license terms in the LICENSE file found in the top-level directory
+// of this distribution and at http://opencv.org/license.html.
+//
+// Copyright (C) 2021 Intel Corporation
+
+#ifndef OPENCV_GAPI_STREAMING_ONEVPL_ONEVPL_SOURCE_HPP
+#define OPENCV_GAPI_STREAMING_ONEVPL_ONEVPL_SOURCE_HPP
+
+#include <opencv2/gapi/garg.hpp>
+#include <opencv2/gapi/streaming/meta.hpp>
+#include <opencv2/gapi/streaming/source.hpp>
+
+namespace cv {
+namespace gapi {
+namespace wip {
+
+class GAPI_EXPORTS OneVPLSource : public IStreamSource
+{
+public:
+    struct Priv;
+
+    explicit OneVPLSource(const std::string& filePath);
+    ~OneVPLSource() override;
+
+    bool pull(cv::gapi::wip::Data& data) override;
+    GMetaArg descr_of() const override;
+
+private:
+    explicit OneVPLSource(std::unique_ptr<Priv>&& impl);
+    std::unique_ptr<Priv> m_priv;
+};
+
+template<class... Args>
+GAPI_EXPORTS_W cv::Ptr<IStreamSource> inline make_vpl_src(const std::string& filePath, Args&&... args)
+{
+    return make_src<OneVPLSource>(filePath, std::forward<Args>(args)...);
+}
+
+} // namespace wip
+} // namespace gapi
+} // namespace cv
+
+#endif // OPENCV_GAPI_STREAMING_ONEVPL_ONEVPL_SOURCE_HPP