diff --git a/src/VideoShader.cpp b/src/VideoShader.cpp
index ee2477b1..bd2c4d30 100644
--- a/src/VideoShader.cpp
+++ b/src/VideoShader.cpp
@@ -437,6 +437,10 @@ void VideoMaterial::bindPlane(int p, bool updateTexture)
         //qDebug("bind PBO %d", p);
         QOpenGLBuffer &pb = d.pbo[p];
         pb.bind();
+        // glMapBuffer() causes sync issue.
+        // Call glBufferData() with NULL pointer before glMapBuffer(), the previous data in PBO will be discarded and
+        // glMapBuffer() returns a new allocated pointer or an unused block immediately even if GPU is still working with the previous data.
+        // https://www.opengl.org/wiki/Buffer_Object_Streaming#Buffer_re-specification
         pb.allocate(pb.size());
         GLubyte* ptr = (GLubyte*)pb.map(QOpenGLBuffer::WriteOnly);
         if (ptr) {
@@ -757,7 +761,8 @@ bool VideoMaterialPrivate::updateTexturesIfNeeded()
     if (update_textures) {
         initTextures(fmt);
         // check pbo support
-        //try_pbo = try_pbo && OpenGLHelper::isPBOSupported();
+        // TODO: complete pbo extension set
+        try_pbo = try_pbo && OpenGLHelper::isPBOSupported();
         // check PBO support with bind() is fine, no need to check extensions
         if (try_pbo) {
             for (int i = 0; i < nb_planes; ++i) {
diff --git a/src/utils/OpenGLHelper.cpp b/src/utils/OpenGLHelper.cpp
index d18152c2..1941d3ac 100644
--- a/src/utils/OpenGLHelper.cpp
+++ b/src/utils/OpenGLHelper.cpp
@@ -20,15 +20,60 @@
 ******************************************************************************/
 
 #include "OpenGLHelper.h"
+#include <string.h> //strstr
 #include <QtCore/QCoreApplication>
 #if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
 #include <QtOpenGL/QGLFunctions>
+#define QOpenGLContext QGLContext
 #endif
 #include "utils/Logger.h"
 
 namespace QtAV {
 namespace OpenGLHelper {
 
+bool hasExtension(const char *exts[])
+{
+    const QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    if (!ctx)
+        return false;
+#if QT_VERSION < QT_VERSION_CHECK(5, 0, 0)
+    const char *ext = (const char*)glGetString(GL_EXTENSIONS);
+    if (!ext)
+        return false;
+#endif
+    for (int i = 0; exts[i]; ++i) {
+#if QT_VERSION >= QT_VERSION_CHECK(5, 0, 0)
+        if (ctx->hasExtension(exts[i]))
+#else
+        if (strstr(ext, exts[i]))
+#endif
+            return true;
+    }
+    return false;
+}
+
+bool isPBOSupported() {
+    // check pbo support
+    static bool support = false;
+    static bool pbo_checked = false;
+    if (pbo_checked)
+        return support;
+    const QOpenGLContext *ctx = QOpenGLContext::currentContext();
+    Q_ASSERT(ctx);
+    if (!ctx)
+        return false;
+    const char* exts[] = {
+        "GL_ARB_pixel_buffer_object",
+        "GL_EXT_pixel_buffer_object",
+        "GL_NV_pixel_buffer_object", //OpenGL ES
+        NULL
+    };
+    support = hasExtension(exts);
+    qDebug() << "PBO: " << support;
+    pbo_checked = true;
+    return support;
+}
+
 // 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/utils/OpenGLHelper.h b/src/utils/OpenGLHelper.h
index 7d6e2aa2..a9e58c48 100644
--- a/src/utils/OpenGLHelper.h
+++ b/src/utils/OpenGLHelper.h
@@ -68,6 +68,13 @@
 namespace QtAV {
 namespace OpenGLHelper {
 
+/*!
+ * \brief hasExtension
+ * Current OpenGL context must be valid.
+ * \param exts Ends with NULL
+ */
+bool hasExtension(const char* exts[]);
+bool isPBOSupported();
 void glActiveTexture(GLenum texture);
 bool videoFormatToGL(const VideoFormat& fmt, GLint* internal_format, GLenum* data_format, GLenum* data_type);
 int bytesOfGLFormat(GLenum format, GLenum dataType = GL_UNSIGNED_BYTE);