Audio playbacK: Don't waste memory on video frames for audio

- we no longer need video buffers to assist with rendering overlays as
they are all handled by OPenGL
- use zero sized buffers
- always set the frame rate to 23.97 as this should be lower than any
actual display refresh - ensuring we don't wait for video buffers we
don't need
- set reference frames to zero.

mythtv/libs/libmythtv/decoders/avformatdecoder.cpp

@@ -2408,18 +2408,9 @@ int AvFormatDecoder::ScanStreams(bool novideo)
     // video params are set properly
     if (m_selectedTrack[kTrackTypeVideo].m_av_stream_index == -1)
     {
-        QString tvformat = gCoreContext->GetSetting("TVFormat").toLower();
-        if (tvformat == "ntsc" || tvformat == "ntsc-jp" ||
-            tvformat == "pal-m" || tvformat == "atsc")
-        {
-            m_fps = 29.97F;
-            m_parent->SetVideoParams(-1, -1, 29.97, 1.0F, false, 16);
-        }
-        else
-        {
-            m_fps = 25.0F;
-            m_parent->SetVideoParams(-1, -1, 25.0, 1.0F, false, 16);
-        }
+        m_fps = 23.97F; // minimum likey display refresh rate
+        // N.B. we know longer need a 'dummy' frame to render overlays into
+        m_parent->SetVideoParams(0, 0, 23.97, 1.0F, false, 0);
     }
 
     if (m_parent->IsErrored())

mythtv/libs/libmythtv/mythplayer.cpp

@@ -622,7 +622,7 @@ void MythPlayer::SetVideoParams(int width, int height, double fps,
 {
     bool paramsChanged = ForceUpdate;
 
-    if (width >= 1 && height >= 1)
+    if (width >= 0 && height >= 0)
     {
         paramsChanged  = true;
         m_videoDim      = m_videoDispDim = QSize(width, height);

mythtv/libs/libmythtv/videooutwindow.cpp

@@ -113,15 +113,6 @@ void VideoOutWindow::MoveResize(void)
     m_videoRect = QRect(QPoint(0, 0), m_videoDispDim);
     m_displayVideoRect = m_displayVisibleRect;
 
-
-    // Avoid too small frames for audio only streams (for OSD).
-    if ((m_videoRect.width() <= 0) || (m_videoRect.height() <= 0))
-    {
-        m_videoDispDim = m_displayVisibleRect.size();
-        m_videoDim     = fix_alignment(m_displayVisibleRect.size());
-        m_videoRect    = QRect(QPoint(0, 0), m_videoDim);
-    }
-
     // Apply various modifications
     ApplyDBScaleAndMove();
     ApplyLetterboxing();