TV: Fix PiP swap

- ensure the main context and other contexts are reset for using null
video and dis/allowing hardware decoders
- ensure there is no deadlock when the decoder for the main context
attempts to call back into the UI thread while holding the global
avlock.

mythtv/libs/libmythtv/playercontext.h

@@ -105,7 +105,7 @@ class MTV_PUBLIC PlayerContext
     void SetPIPLocation(int loc) { m_pipLocation = loc; }
     void SetPIPState(PIPState change) { m_pipState = change; }
     void SetPlayerChangingBuffers(bool val) { m_playerUnsafe = val; }
-    void SetNoHardwareDecoders(void) { m_nohardwaredecoders = true; }
+    void SetNoHardwareDecoders(bool Disallow = true) { m_nohardwaredecoders = Disallow; }
 
     // Gets
     QRect    GetStandAlonePIPRect(void);

mythtv/libs/libmythtv/tv_play.cpp

@@ -6110,6 +6110,8 @@ void TV::RestartAllPlayers(PlayerContext *lctx,
             mctx->m_buffer->Unpause();
     }
 
+    mctx->SetNullVideo(false);
+    mctx->SetNoHardwareDecoders(false);
     bool ok = StartPlayer(mctx, mctx, mctx->GetState());
 
     if (ok)
@@ -6137,6 +6139,20 @@ void TV::RestartAllPlayers(PlayerContext *lctx,
                 pipctx->m_buffer->Unpause();
         }
 
+        pipctx->SetNullVideo(true);
+        pipctx->SetNoHardwareDecoders(true);
+
+        // if the main context is using a hardware decoder, it will callback to
+        // the main thread at some point while holding avcodeclock, which causes
+        // a deadlock. If we can't obtain the lock, try and process the callback.
+        while (!avcodeclock->tryLock(10))
+        {
+            mctx->LockDeletePlayer(__FILE__, __LINE__);
+            if (mctx->m_player)
+                mctx->m_player->ProcessCallbacks();
+            mctx->UnlockDeletePlayer(__FILE__, __LINE__);
+        }
+
         ok = StartPlayer(mctx, pipctx, pipctx->GetState());
 
         if (ok)
@@ -6155,6 +6171,8 @@ void TV::RestartAllPlayers(PlayerContext *lctx,
                 "Failed to restart new pip context (was main context)");
             ForceNextStateNone(pipctx);
         }
+
+        avcodeclock->unlock();
     }
 
     // If old main player had a kMuteAll | kMuteOff setting,