PiP: Add a dummy video sync sub-class for Picture in Picture.

Video timing for PiP's is handled by the main player - hence no actual
video sync is required for the PiP players.

mythtv/libs/libmythtv/mythplayer.cpp

@@ -2116,7 +2116,11 @@ void MythPlayer::VideoStart(void)
     m_double_framerate = false;
     m_scan_tracker     = 2;
 
-    if (using_null_videoout)
+    if (player_ctx->IsPIP() && using_null_videoout)
+    {
+        videosync = new DummyVideoSync(videoOutput, fr_int, 0, false);
+    }
+    else if (using_null_videoout)
     {
         videosync = new USleepVideoSync(videoOutput, fr_int, 0, false);
     }

mythtv/libs/libmythtv/vsync.h

@@ -192,7 +192,7 @@ class BusyWaitVideoSync : public VideoSync
  *   inaccurate on < Linux 2.6 kernels; not very accurate there either.
  *   Not phase-maintaining. Not tried automatically.
  *
- *   This only used when NVP's 'disablevideo' is true (i.e. for 
+ *   This is only used when MythPlayer's 'disablevideo' is true (i.e. for
  *   commercial flagging and for transcoding), since it doesn't
  *   waste CPU cycles busy-waiting like BusyWaitVideoSync.
  */
@@ -208,4 +208,16 @@ class USleepVideoSync : public VideoSync
     bool TryInit(void);
     int WaitForFrame(int sync_delay);
 };
+
+class DummyVideoSync : public VideoSync
+{
+  public:
+    DummyVideoSync(VideoOutput* vo, int fr, int ri, bool intl)
+     : VideoSync(vo, fr, ri, intl) { }
+    ~DummyVideoSync() { }
+
+    QString getName(void) const { return QString("Dummy"); }
+    bool TryInit(void) { return true; }
+    int WaitForFrame(int sync_delay) { return 0; }
+};
 #endif /* VSYNC_H_INCLUDED */