Merge pull request #16031 from aDanPin:dm/streaming_auto_meta

G-API-NG/Streaming: don't require explicit metadata in compileStreaming()

* First probably working version
Hardcode gose to setSource() :)

* Pre final version of move metadata declaration from compileStreaming() to setSource().

* G-API-NG/Streaming: recovered the existing Streaming functionality

- The auto-meta test is disabling since it crashes.
- Restored .gitignore

* G-API-NG/Streaming: Made the meta-less compileStreaming() work

- Works fine even with OpenCV backend;
- Fluid doesn't support such kind of compilation so far - to be fixed

* G-API-NG/Streaming: Fix Fluid to support meta-less compilation

- Introduced a notion of metadata-sensitive passes and slightly
  refactored GCompiler and GFluidBackend to support that
- Fixed a TwoVideoSourcesFail test on streaming

* Add three smoke streaming tests to gapi_streaming_tests.
All three teste run pipeline with two different input sets
1) SmokeTest_Two_Const_Mats test run pipeline with two const Mats
2) SmokeTest_One_Video_One_Const_Scalar test run pipleline with Mat(video source) and const Scalar
3) SmokeTest_One_Video_One_Const_Vector test run pipeline with Mat(video source) and const Vector
 # Please enter the commit message for your changes. Lines starting

* style fix

* Some review stuff

* Some review stuff

modules/gapi/src/api/gbackend.cpp

@@ -56,6 +56,13 @@ void cv::gapi::GBackend::Priv::addBackendPasses(ade::ExecutionEngineSetupContext
     // add custom (backend-specific) graph transformations
 }
 
+void cv::gapi::GBackend::Priv::addMetaSensitiveBackendPasses(ade::ExecutionEngineSetupContext &)
+{
+    // Do nothing by default, plugins may override this to
+    // add custom (backend-specific) graph transformations
+    // which are sensitive to metadata
+}
+
 cv::gapi::GKernelPackage cv::gapi::GBackend::Priv::auxiliaryKernels() const
 {
     return {};

modules/gapi/src/api/gbackend_priv.hpp

@@ -50,14 +50,22 @@ public:
                          const GCompileArgs &args,
                          const std::vector<ade::NodeHandle> &nodes) const;
 
+
     virtual EPtr compile(const ade::Graph   &graph,
                          const GCompileArgs &args,
                          const std::vector<ade::NodeHandle> &nodes,
                          const std::vector<cv::gimpl::Data>& ins_data,
                          const std::vector<cv::gimpl::Data>& outs_data) const;
 
+    // Ask backend to provide general backend-specific compiler passes
     virtual void addBackendPasses(ade::ExecutionEngineSetupContext &);
 
+    // Ask backend to put extra meta-sensitive backend passes Since
+    // the inception of Streaming API one can compile graph without
+    // meta information, so if some passes depend on this information,
+    // they are called when meta information becomes available.
+    virtual void addMetaSensitiveBackendPasses(ade::ExecutionEngineSetupContext &);
+
     virtual cv::gapi::GKernelPackage auxiliaryKernels() const;
 
     virtual ~Priv() = default;

modules/gapi/src/api/gcomputation.cpp

@@ -82,6 +82,12 @@ cv::GStreamingCompiled cv::GComputation::compileStreaming(GMetaArgs &&metas, GCo
     return comp.compileStreaming();
 }
 
+cv::GStreamingCompiled cv::GComputation::compileStreaming(GCompileArgs &&args)
+{
+    cv::gimpl::GCompiler comp(*this, {}, std::move(args));
+    return comp.compileStreaming();
+}
+
 // FIXME: Introduce similar query/test method for GMetaArgs as a building block
 // for functions like this?
 static bool formats_are_same(const cv::GMetaArgs& metas1, const cv::GMetaArgs& metas2)

modules/gapi/src/api/gproto.cpp

@@ -110,6 +110,9 @@ cv::GMetaArg cv::descr_of(const cv::GRunArg &arg)
         case GRunArg::index_of<cv::detail::VectorRef>():
             return cv::GMetaArg(util::get<cv::detail::VectorRef>(arg).descr_of());
 
+        case GRunArg::index_of<cv::gapi::wip::IStreamSource::Ptr>():
+            return cv::util::get<cv::gapi::wip::IStreamSource::Ptr>(arg)->descr_of();
+
         default: util::throw_error(std::logic_error("Unsupported GRunArg type"));
     }
 }