MythFrontend: Add a UPnP Media Server scanner.

N.B. This is disabled for the time being while the UI side is added and
an outstanding thread contention issue is resolved.

This will currently successfully detect other UPnP media servers on the
network (while ignoring the master backend), retrieve and parse their
device descriptions and then subscribe to their event URLs for media
update notifications. Subscriptions are renewed before they expire and
there is initial support for browsing the media available from each
device. Tested with PlayOn, gmediaserver, Windows Media Player 11 and
mediatomb.

The code is entirely event driven, sits its own low priority thread and
should have extremely low resource demands in normal use. Given recent
issues with 'background' events causing playback issues, however, I've
added a minimum level of general logging that should flag up any
scanning activity and thus correlate it with any pauses etc. If a media
server becomes available during playback there may be a small spike in
cpu utilisation while the device description xml file is parsed - though
in testing this has not caused any issues at all.

Additional code is still needed to iterate through and download all the
media metadata available on each server and for UI integration.

Author: Mark Kendall

mythtv/programs/mythfrontend/mediarenderer.cpp

@@ -12,6 +12,8 @@
 #include "mediarenderer.h"
 #include "mythfexml.h"
 #include "compat.h"
+#include "upnpsubscription.h"
+#include "upnpscanner.h"
 
 class MythFrontendStatus : public HttpServerExtension
 {
@@ -272,8 +274,16 @@ MediaRenderer::MediaRenderer()
         // VERBOSE(VB_UPNP, QString( "MediaRenderer::Registering RenderingControl Service." ));
         // m_pHttpServer->RegisterExtension( m_pUPnpRCTL= new UPnpRCTL( RootDevice() ));
 
+        //VERBOSE(VB_UPNP, QString("MediaRenderer: Registering subscription service."));
+        //UPNPSubscription *subscription =
+        //    new UPNPSubscription(m_pHttpServer->m_sSharePath, nPort);
+        //m_pHttpServer->RegisterExtension(subscription);
+
         Start();
 
+        // Start scanning for UPnP media servers
+        //UPNPScanner::Enable(true, subscription);
+
         // ensure the frontend is aware of all backends (slave and master) and
         // other frontends
         SSDP::Instance()->PerformSearch("ssdp:all");

mythtv/programs/mythfrontend/mythfrontend.pro

@@ -38,7 +38,7 @@ HEADERS += videofileassoc.h             videometadatasettings.h
 HEADERS += videoplayercommand.h         videopopups.h
 HEADERS += videofilter.h                videolist.h
 HEADERS += videoplayersettings.h        videodlg.h
-HEADERS += videoglobalsettings.h
+HEADERS += videoglobalsettings.h        upnpscanner.h
 
 SOURCES += main.cpp playbackbox.cpp viewscheduled.cpp audiogeneralsettings.cpp
 SOURCES += globalsettings.cpp manualschedule.cpp programrecpriority.cpp
@@ -58,7 +58,7 @@ SOURCES += videofileassoc.cpp           videometadatasettings.cpp
 SOURCES += videoplayercommand.cpp       videopopups.cpp
 SOURCES += videofilter.cpp              videolist.cpp
 SOURCES += videoplayersettings.cpp      videodlg.cpp
-SOURCES += videoglobalsettings.cpp
+SOURCES += videoglobalsettings.cpp      upnpscanner.cpp
 
 macx {
     mac_bundle {