Improved Device support for V4L2 streams

Allow to reload list of devices, avoid timestamp warning in Loopback, clear UI menu.

src/DeviceSource.cpp

@@ -203,7 +203,7 @@ void Device::remove(GstDevice *device)
     g_free (device_name);
 }
 
-Device::Device(): monitor_initialized_(false), monitor_unplug_event_(false)
+Device::Device(): monitor_(nullptr), monitor_initialized_(false), monitor_unplug_event_(false)
 {
     std::thread(launchMonitoring, this).detach();
 }
@@ -212,6 +212,7 @@ void Device::launchMonitoring(Device *d)
 {
     // gstreamer monitoring of devices
     d->monitor_ = gst_device_monitor_new ();
+    gst_device_monitor_set_show_all_devices(d->monitor_, true);
 
     // watching all video stream sources
     GstCaps *caps = gst_caps_new_empty_simple ("video/x-raw");
@@ -280,6 +281,15 @@ bool Device::initialized()
     return Device::manager().monitor_initialized_;
 }
 
+void Device::reload()
+{
+    if (monitor_ != nullptr) {
+        gst_device_monitor_stop(monitor_);
+        if ( !gst_device_monitor_start (monitor_) )
+            Log::Info("Device discovery start failed.");
+    }
+}
+
 int Device::numDevices()
 {
     access_.lock();

src/DeviceSource.h

@@ -5,7 +5,6 @@
 #include <vector>
 #include <set>
 
-#include "GstToolkit.h"
 #include "StreamSource.h"
 
 class DeviceSource : public StreamSource
@@ -53,19 +52,6 @@ struct DeviceConfig {
         format = "";
     }
 
-    inline DeviceConfig& operator = (const DeviceConfig& b)
-    {
-        if (this != &b) {
-            this->width = b.width;
-            this->height = b.height;
-            this->fps_numerator = b.fps_numerator;
-            this->fps_denominator = b.fps_denominator;
-            this->stream = b.stream;
-            this->format = b.format;
-        }
-        return *this;
-    }
-
     inline bool operator < (const DeviceConfig b) const
     {
         int formatscore = this->format.find("R") != std::string::npos ? 2 : 1; // best score for RGBx
@@ -124,6 +110,7 @@ public:
 
     int  index  (const std::string &device);
     bool exists (const std::string &device) ;
+    void reload ();
 
     static gboolean callback_device_monitor (GstBus *, GstMessage *, gpointer);
     static DeviceConfigSet getDeviceConfigs(const std::string &src_description);

src/Loopback.cpp

@@ -86,7 +86,7 @@ std::string Loopback::init(GstCaps *caps)
         return std::string("Loopback : Invalid caps");
 
     // create a gstreamer pipeline
-    std::string description = "appsrc name=src ! videoconvert ! ";
+    std::string description = "appsrc name=src ! videoconvert ! queue ! ";
 
     // complement pipeline with sink
     description += Loopback::loopback_sink_ + " name=sink";

src/UserInterfaceManager.cpp

@@ -4377,6 +4377,10 @@ void OutputPreview::Render()
                         ImGui::SetCursorPos(draw_pos);
                     }
                 }
+                else {
+                    ImGui::Separator();
+                    ImGui::MenuItem("No active streams", nullptr, false, false);
+                }
 
                 ImGui::EndMenu();
             }
@@ -7484,6 +7488,9 @@ void Navigator::RenderNewPannel()
             // Indication
             ImGui::SameLine();
             ImVec2 pos = ImGui::GetCursorPos();
+            if (ImGuiToolkit::IconButton(5,15,"Reload list"))
+                Device::manager().reload();
+            ImGui::SameLine();
             ImGuiToolkit::HelpToolTip("Create a source capturing video streams from connected devices or machines;\n"
                                      ICON_FA_CARET_RIGHT " webcams or frame grabbers\n"
                                      ICON_FA_CARET_RIGHT " screen capture\n"