diff -r e4ebb16b39ea -r 603d3f8b6302 src/multimedia/qxvideosurface_maemo5.cpp
--- a/src/multimedia/qxvideosurface_maemo5.cpp	Fri Sep 17 08:34:34 2010 +0300
+++ b/src/multimedia/qxvideosurface_maemo5.cpp	Mon Oct 04 01:37:06 2010 +0300
@@ -46,6 +46,8 @@
 
 #include "qxvideosurface_maemo5_p.h"
 
+//#define DEBUG_XV_SURFACE
+
 struct XvFormatRgb
 {
     QVideoFrame::PixelFormat pixelFormat;
@@ -162,6 +164,10 @@
     if (id == m_winId)
         return;
 
+#ifdef DEBUG_XV_SURFACE
+    qDebug() << "QXVideoSurface::setWinId" << id;
+#endif
+
     if (m_image)
         XFree(m_image);
 
@@ -173,6 +179,7 @@
     if (m_portId != 0)
         XvUngrabPort(QX11Info::display(), m_portId, 0);
 
+    QList<QVideoFrame::PixelFormat> prevFormats = m_supportedPixelFormats;
     m_supportedPixelFormats.clear();
     m_formatIds.clear();
 
@@ -195,7 +202,12 @@
         QAbstractVideoSurface::stop();
     }
 
-    emit supportedFormatsChanged();
+    if (m_supportedPixelFormats != prevFormats) {
+#ifdef DEBUG_XV_SURFACE
+        qDebug() << "QXVideoSurface: supportedFormatsChanged";
+#endif
+        emit supportedFormatsChanged();
+    }
 }
 
 QRect QXVideoSurface::displayRect() const
@@ -258,7 +270,9 @@
 
 bool QXVideoSurface::start(const QVideoSurfaceFormat &format)
 {
-    //qDebug() << "QXVideoSurface::start" << format;
+#ifdef DEBUG_XV_SURFACE
+    qDebug() << "QXVideoSurface::start" << format;
+#endif
 
     m_lastFrame = QVideoFrame();
 
@@ -296,7 +310,7 @@
         m_shminfo.readOnly = False;
 
         if (!XShmAttach(QX11Info::display(), &m_shminfo)) {
-            //qDebug() << "XShmAttach failed";
+            qWarning() << "XShmAttach failed" << format;
             return false;
         }
 
@@ -431,7 +445,10 @@
             }
         }
         XvFreeAdaptorInfo(adaptors);
-    }
+    }    
+
+    if (!portFound)
+        qWarning() << "QXVideoSurface::findPort: failed to find XVideo port";
 
     return portFound;
 }
@@ -472,4 +489,9 @@
         }
         XFree(imageFormats);
     }
+
+#ifdef DEBUG_XV_SURFACE
+    qDebug() << "Supported pixel formats:" << m_supportedPixelFormats;
+#endif
+
 }