diff --git a/examples/player/main.cpp b/examples/player/main.cpp
index b406f98b..d5b29d6c 100644
--- a/examples/player/main.cpp
+++ b/examples/player/main.cpp
@@ -75,6 +75,8 @@ void Logger(QtMsgType type, const QMessageLogContext &, const QString& qmsg)
 
 int main(int argc, char *argv[])
 {
+    // has no effect if qInstallMessageHandler() called
+    //qSetMessagePattern("%{function} @%{line}: %{message}");
     QApplication a(argc, argv);
     if (a.arguments().contains("-h") || a.arguments().contains("--help")) {
         qDebug("Usage: %s [-vo qt/gl/d2d/gdi] [url/path]filename", a.applicationFilePath().section(QDir::separator(), -1).toUtf8().constData());
@@ -184,10 +186,9 @@ int main(int argc, char *argv[])
     if (!vd.isEmpty())
         window.setVideoDecoderNames(vd);
 
-
     idx = a.arguments().indexOf("--no-ffmpeg-log");
     idxmax = qMax(idx, idxmax);
-    if (idx < 0)
+    if (idx > 0)
         setFFmpegLogHandler(0);
     bool opt_has_file = argc > idxmax+1;
     if (opt_has_file) {
diff --git a/qml/QmlAV/QQuickItemRenderer.h b/qml/QmlAV/QQuickItemRenderer.h
index 19811a9f..88628cf0 100644
--- a/qml/QmlAV/QQuickItemRenderer.h
+++ b/qml/QmlAV/QQuickItemRenderer.h
@@ -27,8 +27,7 @@
 #include <QtAV/VideoRenderer.h>
 #include <QtQuick/QQuickItem>
 
-namespace QtAV
-{
+namespace QtAV {
 extern QMLAV_EXPORT VideoRendererId VideoRendererId_QQuickItem;
 
 class QQuickItemRendererPrivate;
@@ -85,5 +84,6 @@ private:
 };
 typedef QQuickItemRenderer VideoRendererQQuickItem;
 }
+QML_DECLARE_TYPE(QtAV::QQuickItemRenderer)
 
 #endif // QTAV_QML_QQUICKRENDERER_H
diff --git a/src/AVClock.cpp b/src/AVClock.cpp
index b54273e4..f97da911 100644
--- a/src/AVClock.cpp
+++ b/src/AVClock.cpp
@@ -22,6 +22,7 @@
 
 #include <QtAV/AVClock.h>
 #include <QtCore/QTimerEvent>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/AVCompat.cpp b/src/AVCompat.cpp
index 47bd4180..c8e5dd46 100644
--- a/src/AVCompat.cpp
+++ b/src/AVCompat.cpp
@@ -19,7 +19,7 @@
     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 ******************************************************************************/
 
-#include <QtAV/private/AVCompat.h>
+#include "QtAV/private/AVCompat.h"
 #include "QtAV/version.h"
 #include "QtAV/prepost.h"
 
@@ -68,7 +68,7 @@ void ffmpeg_version_print()
     fflush(0);
 }
 
-PRE_FUNC_ADD(ffmpeg_version_print);
+//PRE_FUNC_ADD(ffmpeg_version_print); //move to Internal::Logger
 
 #ifndef av_err2str
 
diff --git a/src/AVDemuxThread.cpp b/src/AVDemuxThread.cpp
index b48326a6..0f4bb77d 100644
--- a/src/AVDemuxThread.cpp
+++ b/src/AVDemuxThread.cpp
@@ -26,6 +26,7 @@
 #include <QtAV/AVThread.h>
 #include <QtCore/QTimer>
 #include <QtCore/QEventLoop>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/AVDemuxer.cpp b/src/AVDemuxer.cpp
index 629ca90a..ec66aed7 100644
--- a/src/AVDemuxer.cpp
+++ b/src/AVDemuxer.cpp
@@ -27,6 +27,7 @@
 #include "QtAV/Packet.h"
 #include "QAVIOContext.h"
 #include "QtAV/private/AVCompat.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
@@ -165,7 +166,7 @@ AVDemuxer::AVDemuxer(const QString& fileName, QObject *parent)
     class AVInitializer {
     public:
         AVInitializer() {
-            qDebug("av_register_all, avcodec_register_all, avformat_network_init");
+            //qDebug("av_register_all, avcodec_register_all, avformat_network_init");
             avcodec_register_all();
 #if QTAV_HAVE(AVDEVICE)
             avdevice_register_all();
diff --git a/src/AVPlayer.cpp b/src/AVPlayer.cpp
index 8bc18062..fded4f30 100644
--- a/src/AVPlayer.cpp
+++ b/src/AVPlayer.cpp
@@ -48,6 +48,7 @@
 #include "output/OutputSet.h"
 #include "output/video/VideoOutputEventFilter.h"
 #include "QtAV/private/AVCompat.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
@@ -103,7 +104,6 @@ AVPlayer::AVPlayer(QObject *parent) :
 
     mpVOSet = new OutputSet(this);
     mpAOSet = new OutputSet(this);
-    qDebug("%s", aboutQtAV_PlainText().toUtf8().constData());
     /*
      * call stop() before the window(_renderer) closed to stop the waitcondition
      * If close the _renderer widget, the the _renderer may destroy before waking up.
diff --git a/src/AVThread.cpp b/src/AVThread.cpp
index 10499654..a94e65de 100644
--- a/src/AVThread.cpp
+++ b/src/AVThread.cpp
@@ -24,6 +24,7 @@
 #include "QtAV/AVOutput.h"
 #include "QtAV/Filter.h"
 #include "output/OutputSet.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/AudioFormat.cpp b/src/AudioFormat.cpp
index bd51e61c..3fee28fd 100644
--- a/src/AudioFormat.cpp
+++ b/src/AudioFormat.cpp
@@ -20,9 +20,10 @@
 ******************************************************************************/
 
 #include "QtAV/AudioFormat.h"
-#include <QtCore/QtDebug>
 #include "QtAV/private/AVCompat.h"
-
+#ifndef QT_NO_DEBUG_STREAM
+#include <QtDebug>
+#endif //QT_NO_DEBUG_STREAM
 //FF_API_OLD_SAMPLE_FMT. e.g. FFmpeg 0.9
 #ifdef SampleFormat
 #undef SampleFormat
diff --git a/src/AudioResamplerFF.cpp b/src/AudioResamplerFF.cpp
index 232bc266..5ef1ea7f 100644
--- a/src/AudioResamplerFF.cpp
+++ b/src/AudioResamplerFF.cpp
@@ -24,6 +24,7 @@
 #include "QtAV/private/AudioResampler_p.h"
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/prepost.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
@@ -223,6 +224,7 @@ bool AudioResamplerFF::prepare()
     int ret = swr_init(d.context);
     if (ret < 0) {
         qWarning("swr_init failed: %s", av_err2str(ret));
+        swr_free(&d.context);
         return false;
     }
     return true;
diff --git a/src/AudioResamplerLibav.cpp b/src/AudioResamplerLibav.cpp
index 332907ee..bb15421a 100644
--- a/src/AudioResamplerLibav.cpp
+++ b/src/AudioResamplerLibav.cpp
@@ -25,6 +25,7 @@
 #include "QtAV/private/AudioResampler_p.h"
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/prepost.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
@@ -257,6 +258,7 @@ bool AudioResamplerLibav::prepare()
     int ret = swr_init(d.context);
     if (ret < 0) {
         qWarning("swr_init failed: %s", av_err2str(ret));
+        swr_free(&d.context);
         return false;
     }
     return true;
diff --git a/src/AudioThread.cpp b/src/AudioThread.cpp
index 1fb2a0df..a121f388 100644
--- a/src/AudioThread.cpp
+++ b/src/AudioThread.cpp
@@ -30,6 +30,7 @@
 #include "output/OutputSet.h"
 #include "QtAV/private/AVCompat.h"
 #include <QtCore/QCoreApplication>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/Frame.cpp b/src/Frame.cpp
index 11a37cf5..5fa5ba1b 100644
--- a/src/Frame.cpp
+++ b/src/Frame.cpp
@@ -21,6 +21,7 @@
 
 #include "QtAV/Frame.h"
 #include "QtAV/private/Frame_p.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/ImageConverterFF.cpp b/src/ImageConverterFF.cpp
index 222f874f..e72f5b17 100644
--- a/src/ImageConverterFF.cpp
+++ b/src/ImageConverterFF.cpp
@@ -24,6 +24,7 @@
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/private/mkid.h"
 #include "QtAV/prepost.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/ImageConverterIPP.cpp b/src/ImageConverterIPP.cpp
index ef8288ce..5d5f8aa7 100644
--- a/src/ImageConverterIPP.cpp
+++ b/src/ImageConverterIPP.cpp
@@ -30,6 +30,7 @@
 #else
 
 #endif
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/OpenGLVideo.cpp b/src/OpenGLVideo.cpp
index d14cc187..b9337833 100644
--- a/src/OpenGLVideo.cpp
+++ b/src/OpenGLVideo.cpp
@@ -34,6 +34,7 @@
 #include "QtAV/SurfaceInterop.h"
 #include "QtAV/VideoShader.h"
 #include "ShaderManager.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/Packet.cpp b/src/Packet.cpp
index 97118075..05dc1b08 100644
--- a/src/Packet.cpp
+++ b/src/Packet.cpp
@@ -20,6 +20,7 @@
 ******************************************************************************/
 
 #include <QtAV/Packet.h>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/QAVIOContext.cpp b/src/QAVIOContext.cpp
index 42033961..d3b7556d 100644
--- a/src/QAVIOContext.cpp
+++ b/src/QAVIOContext.cpp
@@ -23,6 +23,7 @@
 #include "QAVIOContext.h"
 #include "QtAV/private/AVCompat.h"
 #include <QtCore/QIODevice>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/QtAV/AVClock.h b/src/QtAV/AVClock.h
index cf63e412..aedd3d2d 100644
--- a/src/QtAV/AVClock.h
+++ b/src/QtAV/AVClock.h
@@ -136,7 +136,7 @@ double AVClock::value() const
         if (timer.isValid()) {
             pts_ += double(timer.restart()) * kThousandth;
         } else {//timer is paused
-            qDebug("clock is paused. return the last value %f", pts_);
+            //qDebug("clock is paused. return the last value %f", pts_);
         }
         return pts_ * speed() + value0;
     }
diff --git a/src/QtAV/QtAV_Global.h b/src/QtAV/QtAV_Global.h
index 8c51563a..dd5b671b 100644
--- a/src/QtAV/QtAV_Global.h
+++ b/src/QtAV/QtAV_Global.h
@@ -44,12 +44,11 @@ Q_AV_EXPORT QString QtAV_Version_String_Long();
 namespace QtAV {
 
 enum LogLevel {
-    LogOff = -1,
-    LogDefault = 0,
-    LogDebug,
-    LogWarning,
-    LogCritical,
-    LogFatal,
+    LogOff,
+    LogDebug, // log all
+    LogWarning, // log warning, critical, fatal
+    LogCritical, // log critical, fatal
+    LogFatal, // log fatal
     LogAll
 };
 
@@ -61,6 +60,11 @@ Q_AV_EXPORT void aboutQtAV();
 Q_AV_EXPORT QString aboutQtAV_PlainText();
 Q_AV_EXPORT QString aboutQtAV_HTML();
 
+/*!
+ * The level can also be changed at runtime by setting the QTAV_LOG_LEVEL environment variable;
+ * QTAV_LOG_LEVEL can be: off, debug, warning, critical, fatal, all. Or use their enum values
+ * if both setLogLevel() is called and QTAV_LOG_LEVEL is set, the environment variable takes preceden.
+*/
 Q_AV_EXPORT void setLogLevel(LogLevel value);
 Q_AV_EXPORT LogLevel logLevel();
 
@@ -104,10 +108,5 @@ Q_AV_EXPORT void setFFmpegLogHandler(void(*)(void *, int, const char *, va_list)
 #define Q_FUNC_INFO __FUNCTION__
 #endif
 
-#if defined(BUILD_QTAV_LIB)
-#include "utils/Logger.h"
-//#undef qDebug()
-#endif //BUILD_QTAV_LIB
-
 #endif // QTAV_GLOBAL_H
 
diff --git a/src/QtAV/Statistics.h b/src/QtAV/Statistics.h
index f20e5e25..df152aba 100644
--- a/src/QtAV/Statistics.h
+++ b/src/QtAV/Statistics.h
@@ -116,6 +116,7 @@ public:
         qreal pts() const; // last pts
         // compute from pts history
         qreal currentDisplayFPS() const;
+        //http://ffmpeg.org/faq.html#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e
         //AVStream.avg_frame_rate may be 0, then use AVStream.r_frame_rate
         //http://libav-users.943685.n4.nabble.com/Libav-user-Reading-correct-frame-rate-fps-of-input-video-td4657666.html
         qreal fps_guess;
diff --git a/src/QtAV_Global.cpp b/src/QtAV_Global.cpp
index 5c393d9f..ca5cb003 100644
--- a/src/QtAV_Global.cpp
+++ b/src/QtAV_Global.cpp
@@ -22,7 +22,6 @@
 #include "QtAV/QtAV_Global.h"
 #include <QtCore/QObject>
 #include <QtCore/QRegExp>
-#include <QtDebug>
 #if QTAV_HAVE(WIDGETS)
 #include <QBoxLayout>
 #include <QMessageBox>
@@ -32,13 +31,7 @@
 #endif //QTAV_HAVE(WIDGETS)
 #include "QtAV/version.h"
 #include "QtAV/private/AVCompat.h"
-
-// disable logging for release. you can manually enable it.
-#ifdef QT_NO_DEBUG
-static QtAV::LogLevel gLogLevel = QtAV::LogOff;
-#else
-static QtAV::LogLevel gLogLevel = QtAV::LogAll;
-#endif
+#include "utils/Logger.h"
 
 unsigned QtAV_Version()
 {
@@ -57,6 +50,17 @@ QString QtAV_Version_String_Long()
 
 namespace QtAV {
 
+namespace Internal {
+// disable logging for release. you can manually enable it.
+#ifdef QT_NO_DEBUG
+static QtAV::LogLevel gLogLevel = QtAV::LogOff;
+#else
+static QtAV::LogLevel gLogLevel = QtAV::LogAll;
+#endif
+static bool gLogLevelSet = false;
+bool isLogLevelSet() { return gLogLevelSet;}
+} //namespace Internal
+
 //TODO: auto add new depend libraries information
 void about()
 {
@@ -183,12 +187,13 @@ QString aboutQtAV_HTML()
 
 void setLogLevel(LogLevel value)
 {
-    gLogLevel = value;
+    Internal::gLogLevelSet = true;
+    Internal::gLogLevel = value;
 }
 
 LogLevel logLevel()
 {
-    return (LogLevel)gLogLevel;
+    return (LogLevel)Internal::gLogLevel;
 }
 
 void setFFmpegLogHandler(void (*callback)(void *, int, const char *, va_list))
@@ -203,19 +208,14 @@ static void qtav_ffmpeg_log_callback(void* , int level,const char* fmt, va_list
 {
     QString qmsg = "{FFmpeg} " + QString().vsprintf(fmt, vl);
     qmsg = qmsg.trimmed();
-    QtMsgType mt = QtDebugMsg;
     if (level == AV_LOG_WARNING || level == AV_LOG_ERROR)
-        mt = QtWarningMsg;
+        qWarning() << qmsg;
     else if (level == AV_LOG_FATAL)
-        mt = QtCriticalMsg;
+        qFatal("%s", qmsg.toUtf8().constData());
     else if (level == AV_LOG_PANIC)
-        mt = QtFatalMsg;
-#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
-    QMessageLogContext ctx;
-    qt_message_output(mt, ctx, qmsg);
-#else
-    qt_message_output(mt, qPrintable(qmsg));
-#endif //QT_VERSION
+        qFatal("%s", qmsg.toUtf8().constData());
+    else
+        qDebug() << qmsg;
 }
 
 // TODO: static link. move all into 1
diff --git a/src/VideoCapture.cpp b/src/VideoCapture.cpp
index 30bb6ed9..2c0b1c74 100644
--- a/src/VideoCapture.cpp
+++ b/src/VideoCapture.cpp
@@ -28,6 +28,7 @@
 #include <QtCore/QRunnable>
 #include <QtCore/QThreadPool>
 #include <QtGui/QImage>
+#include "utils/Logger.h"
 
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 #include <QtGui/QDesktopServices>
diff --git a/src/VideoFormat.cpp b/src/VideoFormat.cpp
index fbc5077a..3839d425 100644
--- a/src/VideoFormat.cpp
+++ b/src/VideoFormat.cpp
@@ -20,9 +20,10 @@
 ******************************************************************************/
 
 #include "QtAV/VideoFormat.h"
-#include <QtCore/QtDebug>
 #include <QtCore/QVector>
-
+#ifndef QT_NO_DEBUG_STREAM
+#include <QtDebug>
+#endif
 #include "QtAV/private/AVCompat.h"
 extern "C" {
 #include <libavutil/imgutils.h>
diff --git a/src/VideoShader.cpp b/src/VideoShader.cpp
index aca777e6..dd9494ac 100644
--- a/src/VideoShader.cpp
+++ b/src/VideoShader.cpp
@@ -26,6 +26,7 @@
 #include <cmath>
 #include <QtCore/QCoreApplication>
 #include <QtCore/QFile>
+#include "utils/Logger.h"
 
 /*
  * TODO: glActiveTexture for Qt4
diff --git a/src/VideoThread.cpp b/src/VideoThread.cpp
index c42c85fa..e43f6828 100644
--- a/src/VideoThread.cpp
+++ b/src/VideoThread.cpp
@@ -34,6 +34,7 @@
 #include "output/OutputSet.h"
 #include "QtAV/private/AVCompat.h"
 #include <QtCore/QFileInfo>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/codec/AVDecoder.cpp b/src/codec/AVDecoder.cpp
index 32d69700..c31ae9ca 100644
--- a/src/codec/AVDecoder.cpp
+++ b/src/codec/AVDecoder.cpp
@@ -22,7 +22,7 @@
 #include <QtAV/AVDecoder.h>
 #include <QtAV/private/AVDecoder_p.h>
 #include <QtAV/version.h>
-#include <QtDebug>
+#include "utils/Logger.h"
 
 namespace QtAV {
 AVDecoder::AVDecoder()
diff --git a/src/codec/audio/AudioDecoder.cpp b/src/codec/audio/AudioDecoder.cpp
index 6496b741..f3be58b7 100644
--- a/src/codec/audio/AudioDecoder.cpp
+++ b/src/codec/audio/AudioDecoder.cpp
@@ -24,6 +24,7 @@
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/AudioResampler.h"
 #include "QtAV/AudioResamplerTypes.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/codec/video/VideoDecoder.cpp b/src/codec/video/VideoDecoder.cpp
index 29102986..5029451f 100644
--- a/src/codec/video/VideoDecoder.cpp
+++ b/src/codec/video/VideoDecoder.cpp
@@ -23,6 +23,7 @@
 #include <QtAV/private/VideoDecoder_p.h>
 #include <QtCore/QSize>
 #include "QtAV/private/factory.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/codec/video/VideoDecoderCUDA.cpp b/src/codec/video/VideoDecoderCUDA.cpp
index 9ecf2705..4dca23c3 100644
--- a/src/codec/video/VideoDecoderCUDA.cpp
+++ b/src/codec/video/VideoDecoderCUDA.cpp
@@ -41,6 +41,7 @@
 
 #include "cuda/helper_cuda.h"
 #include "cuda/cuda_api.h"
+#include "utils/Logger.h"
 
 //decode error if not floating context
 
@@ -554,7 +555,9 @@ bool VideoDecoderCUDAPrivate::createCUVIDParser()
 {
     cudaVideoCodec cudaCodec = mapCodecFromFFmpeg(codec_ctx->codec_id);
     if (cudaCodec == -1) {
-        qWarning("CUVID does not support the codec");
+        QString es(QObject::tr("Codec %1 is not supported by CUDA").arg(avcodec_get_name(codec_ctx->codec_id)));
+        //emit error(AVError::CodecError, es);
+        qWarning() << es;
         available = false;
         return false;
     }
diff --git a/src/codec/video/VideoDecoderCedarv.cpp b/src/codec/video/VideoDecoderCedarv.cpp
index 9138def3..7c57c981 100644
--- a/src/codec/video/VideoDecoderCedarv.cpp
+++ b/src/codec/video/VideoDecoderCedarv.cpp
@@ -24,14 +24,12 @@
 #include "QtAV/Packet.h"
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/prepost.h"
-
-#include <QDebug>
-
 #include <libavcodec/avcodec.h>
 extern "C"
 {
 	#include <libcedarv/libcedarv.h>
 }
+#include "utils/Logger.h"
 
 #ifdef NO_NEON_OPT //Don't HAVE_NEON
 static void map32x32_to_yuv_Y(unsigned char* srcY, unsigned char* tarY, unsigned int coded_width, unsigned int coded_height)
diff --git a/src/codec/video/VideoDecoderDXVA.cpp b/src/codec/video/VideoDecoderDXVA.cpp
index 0d53c762..da83b649 100644
--- a/src/codec/video/VideoDecoderDXVA.cpp
+++ b/src/codec/video/VideoDecoderDXVA.cpp
@@ -26,6 +26,7 @@
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/prepost.h"
 #include "utils/GPUMemCopy.h"
+#include "utils/Logger.h"
 
 // TODO: add to QtAV_Compat.h?
 // FF_API_PIX_FMT
diff --git a/src/codec/video/VideoDecoderFFmpeg.cpp b/src/codec/video/VideoDecoderFFmpeg.cpp
index 59fd4d8a..0ab84cac 100644
--- a/src/codec/video/VideoDecoderFFmpeg.cpp
+++ b/src/codec/video/VideoDecoderFFmpeg.cpp
@@ -24,6 +24,7 @@
 #include "QtAV/Packet.h"
 #include "QtAV/private/AVCompat.h"
 #include "QtAV/prepost.h"
+#include "utils/Logger.h"
 
 /*!
  * options (properties) are from libavcodec/options_table.h
diff --git a/src/codec/video/VideoDecoderFFmpegHW.cpp b/src/codec/video/VideoDecoderFFmpegHW.cpp
index a517a382..cd924335 100644
--- a/src/codec/video/VideoDecoderFFmpegHW.cpp
+++ b/src/codec/video/VideoDecoderFFmpegHW.cpp
@@ -21,6 +21,7 @@
 
 #include "QtAV/VideoDecoderFFmpegHW.h"
 #include "QtAV/private/VideoDecoderFFmpegHW_p.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/codec/video/VideoDecoderVAAPI.cpp b/src/codec/video/VideoDecoderVAAPI.cpp
index 45a257e0..1c79fec1 100644
--- a/src/codec/video/VideoDecoderVAAPI.cpp
+++ b/src/codec/video/VideoDecoderVAAPI.cpp
@@ -39,6 +39,7 @@ extern "C" {
 #include "QtAV/prepost.h"
 #include "vaapi/vaapi_helper.h"
 #include "vaapi/SurfaceInteropVAAPI.h"
+#include "utils/Logger.h"
 
 // TODO: add to AVCompat.h?
 // FF_API_PIX_FMT
diff --git a/src/codec/video/VideoDecoderVDA.cpp b/src/codec/video/VideoDecoderVDA.cpp
index c9167481..0c40c9b2 100755
--- a/src/codec/video/VideoDecoderVDA.cpp
+++ b/src/codec/video/VideoDecoderVDA.cpp
@@ -34,6 +34,7 @@ extern "C" {
 }
 #endif //__cplusplus
 #include <VideoDecodeAcceleration/VDADecoder.h>
+#include "utils/Logger.h"
 
 // TODO: add to QtAV_Compat.h?
 // FF_API_PIX_FMT
diff --git a/src/filter/Filter.cpp b/src/filter/Filter.cpp
index 699ff8c1..fbddc831 100644
--- a/src/filter/Filter.cpp
+++ b/src/filter/Filter.cpp
@@ -25,6 +25,7 @@
 #include "QtAV/AVOutput.h"
 #include "QtAV/AVPlayer.h"
 #include "filter/FilterManager.h"
+#include "utils/Logger.h"
 
 /*
  * 1. parent == target (QObject):
diff --git a/src/filter/FilterContext.cpp b/src/filter/FilterContext.cpp
index df1a1c41..3425ff0e 100644
--- a/src/filter/FilterContext.cpp
+++ b/src/filter/FilterContext.cpp
@@ -24,6 +24,7 @@
 #include <QtGui/QPainter>
 #include <QtGui/QTextDocument>
 #include "QtAV/VideoFrame.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/filter/LibAVFilter.cpp b/src/filter/LibAVFilter.cpp
index 3275fcd3..def5d47d 100644
--- a/src/filter/LibAVFilter.cpp
+++ b/src/filter/LibAVFilter.cpp
@@ -25,6 +25,7 @@
 #include "QtAV/Statistics.h"
 #include "QtAV/VideoFrame.h"
 #include "QtAV/private/AVCompat.h"
+#include "utils/Logger.h"
 
 /*
  * libav10.x, ffmpeg2.x: av_buffersink_read deprecated
diff --git a/src/filter/SubtitleFilter.cpp b/src/filter/SubtitleFilter.cpp
index 145fad45..25f0484f 100644
--- a/src/filter/SubtitleFilter.cpp
+++ b/src/filter/SubtitleFilter.cpp
@@ -25,7 +25,7 @@
 #include "QtAV/Subtitle.h"
 #include "QtAV/VideoFrame.h"
 #include <QtCore/QScopedPointer>
-#include <QtDebug>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/AVOutput.cpp b/src/output/AVOutput.cpp
index efa53e69..8d535fe5 100644
--- a/src/output/AVOutput.cpp
+++ b/src/output/AVOutput.cpp
@@ -25,6 +25,7 @@
 #include "QtAV/FilterContext.h"
 #include "filter/FilterManager.h"
 #include "output/OutputSet.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/audio/AudioOutput.cpp b/src/output/audio/AudioOutput.cpp
index 093d7238..2012b3ef 100644
--- a/src/output/audio/AudioOutput.cpp
+++ b/src/output/audio/AudioOutput.cpp
@@ -21,6 +21,7 @@
 
 #include "QtAV/AudioOutput.h"
 #include "QtAV/private/AudioOutput_p.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 AudioOutput::AudioOutput()
diff --git a/src/output/audio/AudioOutputDSound.cpp b/src/output/audio/AudioOutputDSound.cpp
index 22fb159b..7cfbd848 100644
--- a/src/output/audio/AudioOutputDSound.cpp
+++ b/src/output/audio/AudioOutputDSound.cpp
@@ -27,6 +27,7 @@
 #define DIRECTSOUND_VERSION 0x0600
 #include <dsound.h>
 #include "QtAV/private/AVCompat.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 class AudioOutputDSoundPrivate;
diff --git a/src/output/audio/AudioOutputOpenAL.cpp b/src/output/audio/AudioOutputOpenAL.cpp
index 9b589e66..c7d88d5e 100644
--- a/src/output/audio/AudioOutputOpenAL.cpp
+++ b/src/output/audio/AudioOutputOpenAL.cpp
@@ -29,6 +29,7 @@
 #include <AL/al.h>
 #include <AL/alc.h>
 #endif
+#include "utils/Logger.h"
 
 #define UNQUEUE_QUICK 0
 
diff --git a/src/output/audio/AudioOutputOpenSL.cpp b/src/output/audio/AudioOutputOpenSL.cpp
index 29400bfe..f3f83f83 100644
--- a/src/output/audio/AudioOutputOpenSL.cpp
+++ b/src/output/audio/AudioOutputOpenSL.cpp
@@ -21,6 +21,7 @@
 #include <QtCore/QThread>
 #include <SLES/OpenSLES.h>
 #include "QtAV/prepost.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/audio/AudioOutputPortAudio.cpp b/src/output/audio/AudioOutputPortAudio.cpp
index eda3da44..cbb93728 100644
--- a/src/output/audio/AudioOutputPortAudio.cpp
+++ b/src/output/audio/AudioOutputPortAudio.cpp
@@ -25,6 +25,7 @@
 #include "QtAV/prepost.h"
 #include <portaudio.h>
 #include <QtCore/QString>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/Direct2DRenderer.cpp b/src/output/video/Direct2DRenderer.cpp
index c362b309..42a41cdd 100644
--- a/src/output/video/Direct2DRenderer.cpp
+++ b/src/output/video/Direct2DRenderer.cpp
@@ -43,6 +43,7 @@
 //performance: http://msdn.microsoft.com/en-us/library/windows/desktop/dd372260(v=vs.85).aspx
 //vlc is helpful
 //layer(opacity): http://www.cnblogs.com/graphics/archive/2013/04/15/2781969.html
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/GDIRenderer.cpp b/src/output/video/GDIRenderer.cpp
index 2bdb8def..07432c10 100644
--- a/src/output/video/GDIRenderer.cpp
+++ b/src/output/video/GDIRenderer.cpp
@@ -26,6 +26,7 @@
 #include <gdiplus.h>
 #include <QResizeEvent>
 #include "QtAV/prepost.h"
+#include "utils/Logger.h"
 
 #define USE_GRAPHICS 0
 
diff --git a/src/output/video/GLWidgetRenderer.cpp b/src/output/video/GLWidgetRenderer.cpp
index 57468202..31c53ec9 100644
--- a/src/output/video/GLWidgetRenderer.cpp
+++ b/src/output/video/GLWidgetRenderer.cpp
@@ -44,6 +44,7 @@
 
 #include "QtAV/ColorTransform.h"
 #include "QtAV/FilterContext.h"
+#include "utils/Logger.h"
 
 #define UPLOAD_ROI 0
 #define ROI_TEXCOORDS 1
diff --git a/src/output/video/GraphicsItemRenderer.cpp b/src/output/video/GraphicsItemRenderer.cpp
index d0718da5..79a102d6 100644
--- a/src/output/video/GraphicsItemRenderer.cpp
+++ b/src/output/video/GraphicsItemRenderer.cpp
@@ -31,6 +31,7 @@
 #if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
 #include <QtGui/QSurface>
 #endif
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/OpenGLRendererBase.cpp b/src/output/video/OpenGLRendererBase.cpp
index 7e536f9d..0a583578 100644
--- a/src/output/video/OpenGLRendererBase.cpp
+++ b/src/output/video/OpenGLRendererBase.cpp
@@ -31,6 +31,7 @@
 #define QOpenGLShaderProgram QGLShaderProgram
 #define initializeOpenGLFunctions() initializeGLFunctions()
 #endif
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/OpenGLWidgetRenderer.cpp b/src/output/video/OpenGLWidgetRenderer.cpp
index a9ac7969..86f66173 100644
--- a/src/output/video/OpenGLWidgetRenderer.cpp
+++ b/src/output/video/OpenGLWidgetRenderer.cpp
@@ -22,6 +22,7 @@
 #include "QtAV/OpenGLWidgetRenderer.h"
 #include "QtAV/private/OpenGLRendererBase_p.h"
 #include <QResizeEvent>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/OpenGLWindowRenderer.cpp b/src/output/video/OpenGLWindowRenderer.cpp
index d5a7dd9e..54b39dca 100644
--- a/src/output/video/OpenGLWindowRenderer.cpp
+++ b/src/output/video/OpenGLWindowRenderer.cpp
@@ -22,6 +22,7 @@
 #include "QtAV/OpenGLWindowRenderer.h"
 #include "QtAV/private/OpenGLRendererBase_p.h"
 #include <QResizeEvent>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/VideoOutputEventFilter.cpp b/src/output/video/VideoOutputEventFilter.cpp
index 453ff9e1..5042649c 100644
--- a/src/output/video/VideoOutputEventFilter.cpp
+++ b/src/output/video/VideoOutputEventFilter.cpp
@@ -24,6 +24,7 @@
 #include <QtCore/QEvent>
 #include <QKeyEvent>
 #include <QWidget>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/VideoRenderer.cpp b/src/output/video/VideoRenderer.cpp
index b1aad2d2..a29178b9 100644
--- a/src/output/video/VideoRenderer.cpp
+++ b/src/output/video/VideoRenderer.cpp
@@ -30,6 +30,7 @@
 #if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
 #include <QtGui/QWindow>
 #endif
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/WidgetRenderer.cpp b/src/output/video/WidgetRenderer.cpp
index c6f36060..091e8d28 100644
--- a/src/output/video/WidgetRenderer.cpp
+++ b/src/output/video/WidgetRenderer.cpp
@@ -26,6 +26,7 @@
 #include <QApplication>
 #include <QResizeEvent>
 #include "QtAV/Filter.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/output/video/XVRenderer.cpp b/src/output/video/XVRenderer.cpp
index 35e2d780..c74c5d65 100644
--- a/src/output/video/XVRenderer.cpp
+++ b/src/output/video/XVRenderer.cpp
@@ -27,11 +27,15 @@
 #include <QWidget>
 #include <QResizeEvent>
 #include <QtCore/qmath.h>
+//#error qtextstream.h must be included before any header file that defines Status. Xlib.h defines Status
+#include <QtCore/QTextStream> //build error
 #include <sys/shm.h>
 #include <X11/Xlib.h>
 #include <X11/extensions/Xvlib.h>
 #include "QtAV/prepost.h"
 
+#include "utils/Logger.h"
+
 //http://huangbster.i.sohu.com/blog/view/256490057.htm
 
 namespace QtAV {
diff --git a/src/subtitle/CharsetDetector.cpp b/src/subtitle/CharsetDetector.cpp
index c1fd501a..0deb9509 100644
--- a/src/subtitle/CharsetDetector.cpp
+++ b/src/subtitle/CharsetDetector.cpp
@@ -23,7 +23,7 @@
 #include "QtAV/QtAV_Global.h"
 #include <cassert>
 #include <QtCore/QLibrary>
-#include <QtDebug>
+#include "utils/Logger.h"
 
 #if QTAV_HAVE(CHARDET)
 #include <chardet.h>
diff --git a/src/subtitle/Subtitle.cpp b/src/subtitle/Subtitle.cpp
index 5c098dca..54feeb02 100644
--- a/src/subtitle/Subtitle.cpp
+++ b/src/subtitle/Subtitle.cpp
@@ -22,7 +22,6 @@
 #include "QtAV/Subtitle.h"
 #include "QtAV/private/SubtitleProcessor.h"
 #include <algorithm>
-#include <QtDebug>
 #include <QtCore/QBuffer>
 #include <QtCore/QDir>
 #include <QtCore/QFile>
@@ -36,6 +35,7 @@
 #include <QtCore/QTextStream>
 #include <QtCore/QMutexLocker>
 #include "subtitle/CharsetDetector.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/subtitle/SubtitleProcessor.cpp b/src/subtitle/SubtitleProcessor.cpp
index bcdccce7..b2709739 100644
--- a/src/subtitle/SubtitleProcessor.cpp
+++ b/src/subtitle/SubtitleProcessor.cpp
@@ -23,7 +23,7 @@
 #include "QtAV/FactoryDefine.h"
 #include "QtAV/private/factory.h"
 #include <QtCore/QFile>
-#include <QtDebug>
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/subtitle/SubtitleProcessorFFmpeg.cpp b/src/subtitle/SubtitleProcessorFFmpeg.cpp
index e8cf99b9..f18a2cc8 100644
--- a/src/subtitle/SubtitleProcessorFFmpeg.cpp
+++ b/src/subtitle/SubtitleProcessorFFmpeg.cpp
@@ -20,13 +20,13 @@
 ******************************************************************************/
 
 #include <string>
-#include <QtDebug>
 #include "QtAV/private/SubtitleProcessor.h"
 #include "QtAV/prepost.h"
 #include "QtAV/AVDemuxer.h"
 #include "QtAV/Packet.h"
 #include "QtAV/private/AVCompat.h"
 #include "PlainText.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
diff --git a/src/subtitle/SubtitleProcessorLibASS.cpp b/src/subtitle/SubtitleProcessorLibASS.cpp
index e4ad201c..061e50a6 100644
--- a/src/subtitle/SubtitleProcessorLibASS.cpp
+++ b/src/subtitle/SubtitleProcessorLibASS.cpp
@@ -24,11 +24,11 @@
 extern "C" {
 #include <ass/ass.h>
 }
-#include <QtDebug>
 #include "QtAV/private/SubtitleProcessor.h"
 #include "QtAV/prepost.h"
 #include "QtAV/Packet.h"
 #include "PlainText.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 
@@ -76,14 +76,24 @@ void RegisterSubtitleProcessorLibASS_Man()
     FACTORY_REGISTER_ID_MAN(SubtitleProcessor, LibASS, kName)
 }
 
+// log level from ass_utils.h
+#define MSGL_FATAL 0
+#define MSGL_ERR 1
+#define MSGL_WARN 2
+#define MSGL_INFO 4
+#define MSGL_V 6
+#define MSGL_DBG2 7
+
 static void msg_callback(int level, const char *fmt, va_list va, void *data)
 {
     Q_UNUSED(data)
-    if (level > 6)
-        return;
-    printf("libass: ");
-    vprintf(fmt, va);
-    printf("\n");
+    QString msg("{libass} " + QString().vsprintf(fmt, va));
+    if (level == MSGL_FATAL)
+        qFatal("%s", msg.toUtf8().constData());
+    else if (level <= 2)
+        qWarning() << msg;
+    else if (level <= MSGL_INFO)
+        qDebug() << msg;
 }
 
 SubtitleProcessorLibASS::SubtitleProcessorLibASS()
@@ -180,7 +190,7 @@ bool SubtitleProcessorLibASS::process(const QString &path)
     }
     m_track = ass_read_file(m_ass, (char*)path.toUtf8().constData(), NULL);
     if (!m_track) {
-        qWarning("ass_read_memory error, ass track init failed!");
+        qWarning("ass_read_file error, ass track init failed!");
         return false;
     }
     processTrack(m_track);
diff --git a/src/utils/BlockingQueue.h b/src/utils/BlockingQueue.h
index f750e41c..1c79afdc 100644
--- a/src/utils/BlockingQueue.h
+++ b/src/utils/BlockingQueue.h
@@ -89,7 +89,7 @@ BlockingQueue<T, Container>::BlockingQueue()
 template <typename T, template <typename> class Container>
 void BlockingQueue<T, Container>::setCapacity(int max)
 {
-    qDebug("queue capacity==>>%d", max);
+    //qDebug("queue capacity==>>%d", max);
     QWriteLocker locker(&lock);
     Q_UNUSED(locker);
     cap = max;
@@ -98,7 +98,7 @@ void BlockingQueue<T, Container>::setCapacity(int max)
 template <typename T, template <typename> class Container>
 void BlockingQueue<T, Container>::setThreshold(int min)
 {
-    qDebug("queue threshold==>>%d", min);
+    //qDebug("queue threshold==>>%d", min);
     QWriteLocker locker(&lock);
     Q_UNUSED(locker);
     thres = min;
diff --git a/src/utils/Logger.cpp b/src/utils/Logger.cpp
index 37ccba8a..9035dfe4 100644
--- a/src/utils/Logger.cpp
+++ b/src/utils/Logger.cpp
@@ -22,58 +22,78 @@
 /*!
  * DO NOT appear qDebug, qWanring etc in Logger.cpp! They are undefined and redefined to QtAV:Internal::Logger.xxx
  */
-//#include "Logger.h"
 // we need LogLevel so must include QtAV_Global.h
+#include <QtCore/QString>
 #include "QtAV/QtAV_Global.h"
+#include "Logger.h"
 
+#ifdef HACK_QT_LOG
+
+void ffmpeg_version_print();
 namespace QtAV {
 namespace Internal {
+static QString gQtAVLogTag("");
+
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 typedef Logger::Context QMessageLogger;
 #endif
 
 static void log_helper(QtMsgType msgType, const QMessageLogger *qlog, const char* msg, va_list ap) {
-    QString qmsg;
+    QString qmsg(gQtAVLogTag);
     if (msg)
-        qmsg = "<QtAV> " + QString().vsprintf(msg, ap);
+        qmsg += QString().vsprintf(msg, ap);
     // qt_message_output is a public api
-#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
-    if (qlog) {
-        qlog->debug() << qmsg;
-    } else {
+#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
+    qt_message_output(msgType, qmsg.toUtf8().constData());
+    return;
+#else
+    if (!qlog) {
         QMessageLogContext ctx;
         qt_message_output(msgType, ctx, qmsg);
+        return;
     }
+#endif
+#ifndef QT_NO_DEBUG_STREAM
+    if (msgType == QtWarningMsg)
+        qlog->warning() << qmsg;
+    else if (msgType == QtCriticalMsg)
+        qlog->critical() << qmsg;
+    else if (msgType == QtFatalMsg)
+        qlog->fatal("%s", qmsg.toUtf8().constData());
+    else
+        qlog->debug() << qmsg;
 #else
-    qt_message_output(msgType, qPrintable(qmsg));
-#endif //QT_VERSION
+    if (msgType == QtFatalMsg)
+        qlog->fatal("%s", qmsg.toUtf8().constData());
+#endif //
 }
 
 // macro does not support A::##X
 
 void Logger::debug(const char *msg, ...) const
 {
-    QtAVDebug d(QtDebugMsg); // initialize something. e.g. environment check
+    QtAVDebug d; // initialize something. e.g. environment check
     Q_UNUSED(d);
     const int v = (int)logLevel();
-    if (v < (int)LogDebug)
+    if (v <= (int)LogOff)
         return;
-    if (v > (int)LogDebug && v != (int)LogAll)
+    if (v > (int)LogDebug && v < (int)LogAll)
         return;
     va_list ap;
     va_start(ap, msg);
+    // can not use ctx.debug() <<... because QT_NO_DEBUG_STREAM maybe defined
     log_helper(QtDebugMsg, &ctx, msg, ap);
     va_end(ap);
 }
 
 void Logger::warning(const char *msg, ...) const
 {
-    QtAVDebug d(QtWarningMsg); // initialize something. e.g. environment check
+    QtAVDebug d; // initialize something. e.g. environment check
     Q_UNUSED(d);
     const int v = (int)logLevel();
-    if (v < (int)LogWarning)
+    if (v <= (int)LogOff)
         return;
-    if (v > (int)LogWarning && v != (int)LogAll)
+    if (v > (int)LogWarning && v < (int)LogAll)
         return;
     va_list ap;
     va_start(ap, msg);
@@ -83,12 +103,12 @@ void Logger::warning(const char *msg, ...) const
 
 void Logger::critical(const char *msg, ...) const
 {
-    QtAVDebug d(QtCriticalMsg); // initialize something. e.g. environment check
+    QtAVDebug d; // initialize something. e.g. environment check
     Q_UNUSED(d);
     const int v = (int)logLevel();
-    if (v < (int)LogCritical)
+    if (v <= (int)LogOff)
         return;
-    if (v > (int)LogCritical && v != (int)LogAll)
+    if (v > (int)LogCritical && v < (int)LogAll)
         return;
     va_list ap;
     va_start(ap, msg);
@@ -98,62 +118,93 @@ void Logger::critical(const char *msg, ...) const
 
 void Logger::fatal(const char *msg, ...) const
 {
-    QtAVDebug d(QtFatalMsg); // initialize something. e.g. environment check
+    QtAVDebug d; // initialize something. e.g. environment check
     Q_UNUSED(d);
     const int v = (int)logLevel();
-    if (v < (int)LogFatal)
-        return;
-    if (v > (int)LogFatal && v != (int)LogAll)
-        return;
-    va_list ap;
-    va_start(ap, msg);
-    log_helper(QtFatalMsg, &ctx, msg, ap);
-    va_end(ap);
+    /*
+    if (v <= (int)LogOff)
+        abort();
+    if (v > (int)LogFatal && v < (int)LogAll)
+        abort();
+    */
+    if (v > (int)LogOff) {
+        va_list ap;
+        va_start(ap, msg);
+        log_helper(QtFatalMsg, &ctx, msg, ap);
+        va_end(ap);
+    }
+    abort();
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 #ifndef QT_NO_DEBUG_STREAM
+// internal used by Logger::fatal(const char*,...) with log level checked, so always do things here
+void Logger::Context::fatal(const char *msg, ...) const
+{
+    va_list ap;
+    va_start(ap, msg);
+    QString qmsg;
+    if (msg)
+        qmsg += QString().vsprintf(msg, ap);
+    qt_message_output(QtFatalMsg, qmsg.toUtf8().constData());
+    va_end(ap);
+    abort();
+}
+#endif //QT_NO_DEBUG_STREAM
+#endif //QT_VERSION
+
+#ifndef QT_NO_DEBUG_STREAM
+// will print message in ~QDebug()
+// can not use QDebug on stack. It must lives in QtAVDebug
 QtAVDebug Logger::debug() const
 {
-    if ((int)logLevel() < (int)LogDebug)
-        return QtAVDebug(QtDebugMsg);
-    // will print message in ~QDebug()
-    // can not use QDebug on stack. It must lives in QtAVDebug
-    return QtAVDebug(QtDebugMsg, new QDebug(ctx.debug()));
+    QtAVDebug d(QtDebugMsg); //// initialize something. e.g. environment check
+    const int v = (int)logLevel();
+    if (v <= (int)LogOff)
+        return d;
+    if (v <= (int)LogDebug || v >= (int)LogAll)
+        d.setQDebug(new QDebug(ctx.debug()));
+    return d;
 }
 
 QtAVDebug Logger::warning() const
 {
-    if ((int)logLevel() < (int)LogWarning)
-        return QtAVDebug(QtWarningMsg);
-    return QtAVDebug(QtWarningMsg, new QDebug(ctx.warning()));
+    QtAVDebug d(QtWarningMsg);
+    const int v = (int)logLevel();
+    if (v <= (int)LogOff)
+        return d;
+    if (v <= (int)LogWarning || v >= (int)LogAll)
+        d.setQDebug(new QDebug(ctx.warning()));
+    return d;
 }
 
 QtAVDebug Logger::critical() const
 {
-    if ((int)logLevel() < (int)LogCritical)
-        return QtAVDebug(QtCriticalMsg);
-    return QtAVDebug(QtCriticalMsg, new QDebug(ctx.critical()));
+    QtAVDebug d(QtCriticalMsg);
+    const int v = (int)logLevel();
+    if (v <= (int)LogOff)
+        return d;
+    if (v <= (int)LogCritical || v >= (int)LogAll)
+        d.setQDebug(new QDebug(ctx.critical()));
+    return d;
 }
 // no QMessageLogger::fatal()
-/*
-QtAVDebug Logger::fatal() const
-{
-    if ((int)logLevel() < (int)LogFatal)
-        return QtAVDebug(QtFatalMsg);
-    return QtAVDebug(QtFatalMsg, new QDebug(ctx.fatal()));
-}*/
 #endif //QT_NO_DEBUG_STREAM
 
+bool isLogLevelSet();
+
 QtAVDebug::QtAVDebug(QtMsgType t, QDebug *d)
     : type(t)
-    , dbg(d)
+    , dbg(0)
 {
+    setQDebug(d); // call *dbg << gQtAVLogTag
     static bool sFirstRun = true;
     if (!sFirstRun)
         return;
     sFirstRun = false;
     //printf("Qt Logging first run........\n");
     // check environment var and call other functions at first Qt logging call
+    // always override setLogLevel()
     QByteArray env = qgetenv("QTAV_LOG_LEVEL");
     if (!env.isEmpty()) {
         bool ok = false;
@@ -181,13 +232,31 @@ QtAVDebug::QtAVDebug(QtMsgType t, QDebug *d)
                 setLogLevel(LogAll);
         }
     }
+    env = qgetenv("QTAV_LOG_TAG");
+    if (!env.isEmpty()) {
+        gQtAVLogTag = env;
+    }
+
+    if ((int)logLevel() > (int)LogOff) {
+        ffmpeg_version_print();
+        printf("%s\n", aboutQtAV_PlainText().toUtf8().constData());
+        fflush(0);
+    }
 }
 
 QtAVDebug::~QtAVDebug()
+{
+    setQDebug(0);
+}
+
+void QtAVDebug::setQDebug(QDebug *d)
 {
     if (dbg) {
         delete dbg;
-        dbg = 0;
+    }
+    dbg = d;
+    if (dbg && !gQtAVLogTag.isEmpty()) {
+        *dbg << gQtAVLogTag;
     }
 }
 
@@ -208,3 +277,5 @@ QtAVDebug debug(const char *msg, ...)
 
 } //namespace Internal
 } // namespace QtAV
+
+#endif //HACK_QT_LOG
diff --git a/src/utils/Logger.h b/src/utils/Logger.h
index fb7be5b8..06183afa 100644
--- a/src/utils/Logger.h
+++ b/src/utils/Logger.h
@@ -21,12 +21,25 @@
 
 /*
  * Qt Logging Hack
+ * in qmacdefines_mac.h, if qDebug is defined, then if will be defined as QT_NO_QDEBUG_MACRO, don't know why
+ * So you have to include this only as the last #include in cpp file!
+ * DO NOT use qDebug in public header!
  */
 
 #ifndef QTAV_LOGGER_H
 #define QTAV_LOGGER_H
 
+/*!
+  Environment var
+  QTAV_LOG_TAG: prefix the value to log message
+  QTAV_LOG_LEVEL: set log level, can be "off", "debug", "warning", "critical", "fatal", "all"
+ */
+
+#define HACK_QT_LOG
+#ifdef HACK_QT_LOG
+
 #include <QtDebug>
+#include <QtAV/QtAV_Global.h>
 
 #ifndef Q_DECL_CONSTEXPR
 #define Q_DECL_CONSTEXPR
@@ -53,34 +66,54 @@ public:
      */
     QtAVDebug(QtMsgType t = QtDebugMsg, QDebug *d = 0);
     ~QtAVDebug();
+    void setQDebug(QDebug* d);
+    // QDebug api
+    inline QtAVDebug &space() {
+        if (dbg)
+            dbg->space();
+        return *this;
+    }
+    inline QtAVDebug &nospace() {
+        if (dbg)
+            dbg->nospace();
+        return *this;
+    }
+    inline QtAVDebug &maybeSpace() {
+        if (dbg)
+            dbg->maybeSpace();
+        return *this;
+    }
+
     template<typename T> QtAVDebug &operator<<(T t) {
         if (!dbg)
             return *this;
-        if ((int)logLevel() < LogDebug)
+        const int l = (int)logLevel();
+        if (l <= (int)LogOff)
             return *this;
-        if ((int)logLevel() >= LogAll) {
+        if (l >= (int)LogAll) {
             *dbg << t;
             return *this;
         }
-        if ((int)logLevel() <= LogDebug) {
+        if (l == (int)LogDebug) {
             *dbg << t;
             return *this;
         }
-        if (logLevel() == LogWarning) {
-            if ((int)type <= (int)QtWarningMsg)
+        if (l == (int)LogWarning) {
+            if ((int)type >= (int)QtWarningMsg)
                 *dbg << t;
             return *this;
         }
-        if (logLevel() == LogCritical) {
-            if ((int)type <= (int)QtCriticalMsg)
+        if (l == (int)LogCritical) {
+            if ((int)type >= (int)QtCriticalMsg)
                 *dbg << t;
             return *this;
         }
-        if (logLevel() == LogFatal) {
-            if ((int)type <= (int)QtFatalMsg)
+        if (l == (int)LogFatal) {
+            if ((int)type >= (int)QtFatalMsg)
                 *dbg << t;
             return *this;
         }
+        return *this;
     }
 private:
     QtMsgType type;
@@ -92,7 +125,7 @@ class Logger {
 public:Q_DECL_CONSTEXPR Logger(const char *file = "unknown", int line = 0, const char *function = "unknown", const char *category = "default")
         : ctx(file, line, function, category) {}
     void debug(const char *msg, ...) const Q_ATTRIBUTE_FORMAT_PRINTF(2, 3);
-    void noDebug(const char *msg, ...) const Q_ATTRIBUTE_FORMAT_PRINTF(2, 3)
+    void noDebug(const char *, ...) const Q_ATTRIBUTE_FORMAT_PRINTF(2, 3)
     {}
     void warning(const char *msg, ...) const Q_ATTRIBUTE_FORMAT_PRINTF(2, 3);
     void critical(const char *msg, ...) const Q_ATTRIBUTE_FORMAT_PRINTF(2, 3);
@@ -105,7 +138,7 @@ public:Q_DECL_CONSTEXPR Logger(const char *file = "unknown", int line = 0, const
 
 #ifndef QT_NO_DEBUG_STREAM
     //TODO: QLoggingCategory
-    QtAVDebug debug() const ;
+    QtAVDebug debug() const;
     QtAVDebug warning() const;
     QtAVDebug critical() const;
     //QtAVDebug fatal() const;
@@ -118,6 +151,10 @@ public: //public can typedef outside
     public:
         Q_DECL_CONSTEXPR Context(const char *fileName, int lineNumber, const char *functionName, const char *categoryName)
             : version(1), line(lineNumber), file(fileName), function(functionName), category(categoryName) {}
+#ifndef Q_CC_MSVC
+        Q_NORETURN
+#endif
+        void fatal(const char *msg, ...) const Q_DECL_NOTHROW Q_ATTRIBUTE_FORMAT_PRINTF(2, 3);
 #ifndef QT_NO_DEBUG_STREAM
         inline QDebug debug() const { return QDebug(QtDebugMsg);}
         inline QDebug warning() const { return QDebug(QtWarningMsg);}
@@ -159,12 +196,32 @@ QNoDebug debug(const char *msg, ...); /* print debug message */
 #undef qWarning
 #undef qCritical
 #undef qFatal
+// debug and warning output can be disabled at build time in Qt
+// from qdebug.h
+
+#ifdef QT_NO_DEBUG_OUTPUT
+#define QT_NO_WARNING_OUTPUT ////FIXME. qWarning() => Logger.warning() not declared
+#undef qDebug
+inline QNoDebug qDebug() { return QNoDebug(); }
+#define qDebug QT_NO_QDEBUG_MACRO
+#else
+inline QtAVDebug qDebug() { return QtAVDebug(QtDebugMsg); }
 #define qDebug QtAV::Internal::Logger(__FILE__, __LINE__, Q_FUNC_INFO).debug
+#endif //QT_NO_DEBUG_OUTPUT
+
+#ifdef QT_NO_WARNING_OUTPUT
+#undef qWarning
+inline QNoDebug qWarning() { return QNoDebug(); }
+#define qWarning QT_NO_QWARNING_MACRO
+#else
+inline QtAVDebug qWarning() { return QtAVDebug(QtWarningMsg); }
 #define qWarning QtAV::Internal::Logger(__FILE__, __LINE__, Q_FUNC_INFO).warning
+#endif //QT_NO_WARNING_OUTPUT
 #define qCritical QtAV::Internal::Logger(__FILE__, __LINE__, Q_FUNC_INFO).critical
 #define qFatal QtAV::Internal::Logger(__FILE__, __LINE__, Q_FUNC_INFO).fatal
 
 } // namespace Internal
 } // namespace QtAV
 
+#endif //HACK_QT_LOG
 #endif // QTAV_LOGGER_H
diff --git a/src/utils/OpenGLHelper.cpp b/src/utils/OpenGLHelper.cpp
index 4a474622..7fba19a8 100644
--- a/src/utils/OpenGLHelper.cpp
+++ b/src/utils/OpenGLHelper.cpp
@@ -23,10 +23,11 @@
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 #include <QtOpenGL/QGLFunctions>
 #endif
+#include "utils/Logger.h"
+
 namespace QtAV {
 namespace OpenGLHelper {
 
-
 // glActiveTexture in Qt4 on windows release mode crash for me
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 #ifndef QT_OPENGL_ES
diff --git a/src/vaapi/vaapi_helper.cpp b/src/vaapi/vaapi_helper.cpp
index 25359243..75fef7b4 100644
--- a/src/vaapi/vaapi_helper.cpp
+++ b/src/vaapi/vaapi_helper.cpp
@@ -1,4 +1,5 @@
 #include "vaapi_helper.h"
+#include "utils/Logger.h"
 
 namespace QtAV {
 namespace vaapi {
diff --git a/src/vaapi/vaapi_helper.h b/src/vaapi/vaapi_helper.h
index 04be3cdd..fbb4deeb 100644
--- a/src/vaapi/vaapi_helper.h
+++ b/src/vaapi/vaapi_helper.h
@@ -203,7 +203,7 @@ public:
         , m_height(h)
     {}
     ~surface_t() {
-        qDebug("VAAPI - destroying surface 0x%x", (int)m_id);
+        //qDebug("VAAPI - destroying surface 0x%x", (int)m_id);
         if (m_id != VA_INVALID_SURFACE)
             VAWARN(vaDestroySurfaces(m_display->get(), &m_id, 1))
     }