Merge pull request #20832 from TolyaTalamanov:at/python-gstreamer-source

G-API: Wrap GStreamerSource

* Wrap GStreamerSource into python

* Fixed test skipping when can't make Gst-src

* Wrapped GStreamerPipeline class, added dummy test for it

* Fix no_gst testing

* Changed wrap for GStreamerPipeline::getStreamingSource() : now python-specific in-class method GStreamerPipeline::get_streaming_source()

* Added accuracy tests vs OCV:VideoCapture(Gstreamer)

* Add skipping when can't use VideoCapture(GSTREAMER);
Add better handling of GStreamer backend unavailable;
Changed video to avoid terminations

* Applying comments

* back to a separate get_streaming_source function, with comment

Co-authored-by: OrestChura <orest.chura@intel.com>

modules/gapi/include/opencv2/gapi/streaming/gstreamer/gstreamerpipeline.hpp

@@ -19,12 +19,12 @@ namespace gapi {
 namespace wip {
 namespace gst {
 
-class GAPI_EXPORTS GStreamerPipeline
+class GAPI_EXPORTS_W GStreamerPipeline
 {
 public:
     class Priv;
 
-    explicit GStreamerPipeline(const std::string& pipeline);
+    GAPI_WRAP explicit GStreamerPipeline(const std::string& pipeline);
     IStreamSource::Ptr getStreamingSource(const std::string& appsinkName,
                                           const GStreamerSource::OutputType outputType =
                                               GStreamerSource::OutputType::MAT);
@@ -40,6 +40,18 @@ protected:
 
 using GStreamerPipeline = gst::GStreamerPipeline;
 
+// NB: Function for using from python
+// FIXME: a separate function is created due to absence of wrappers for `shared_ptr<> `
+// Ideally would be to wrap the `GStreamerPipeline::getStreamingSource()` method as is
+GAPI_EXPORTS_W cv::Ptr<IStreamSource>
+inline get_streaming_source(cv::Ptr<GStreamerPipeline>& pipeline,
+                            const std::string& appsinkName,
+                            const GStreamerSource::OutputType outputType
+                                = GStreamerSource::OutputType::MAT)
+{
+    return pipeline->getStreamingSource(appsinkName, outputType);
+}
+
 } // namespace wip
 } // namespace gapi
 } // namespace cv

modules/gapi/include/opencv2/gapi/streaming/gstreamer/gstreamersource.hpp

@@ -82,6 +82,14 @@ protected:
 
 using GStreamerSource = gst::GStreamerSource;
 
+// NB: Overload for using from python
+GAPI_EXPORTS_W cv::Ptr<IStreamSource>
+inline make_gst_src(const std::string& pipeline,
+                    const GStreamerSource::OutputType outputType =
+                    GStreamerSource::OutputType::MAT)
+{
+    return make_src<GStreamerSource>(pipeline, outputType);
+}
 } // namespace wip
 } // namespace gapi
 } // namespace cv