diff --git a/src/PacketBuffer.cpp b/src/PacketBuffer.cpp
index 464119a0..a2388850 100644
--- a/src/PacketBuffer.cpp
+++ b/src/PacketBuffer.cpp
@@ -25,6 +25,7 @@ namespace QtAV {
 
 PacketBuffer::PacketBuffer()
     : m_mode(BufferTime)
+    , m_buffering(true) // in buffering state at the beginning
     , m_buffer(0)
     , m_value0(0)
     , m_value1(0)
@@ -70,6 +71,11 @@ int PacketBuffer::buffered() const
     return m_value1 - m_value0;
 }
 
+bool PacketBuffer::isBuffering() const
+{
+    return m_buffering;
+}
+
 qreal PacketBuffer::bufferProgress() const
 {
     const qreal p = qreal(buffered())/qreal(bufferValue());
@@ -78,12 +84,12 @@ qreal PacketBuffer::bufferProgress() const
 
 bool PacketBuffer::checkEnough() const
 {
-    return m_value1 - m_value0 >= m_buffer;
+    return buffered() >= bufferValue();
 }
 
 bool PacketBuffer::checkFull() const
 {
-    return m_value1 - m_value0 >= 2*m_buffer;
+    return buffered() >= 2*bufferValue();
 }
 
 void PacketBuffer::onPut(const Packet &p)
@@ -95,10 +101,19 @@ void PacketBuffer::onPut(const Packet &p)
     } else {
         m_value1++;
     }
+    // TODO: compute buffer speed (and auto set the best bufferValue)
+    if (!m_buffering)
+        return;
+    if (checkEnough()) {
+        m_buffering = false;
+    }
 }
 
 void PacketBuffer::onTake(const Packet &p)
 {
+    if (checkEmpty()) {
+        m_buffering = true;
+    }
     if (queue.isEmpty()) {
         m_value0 = 0;
         m_value1 = 0;
diff --git a/src/PacketBuffer.h b/src/PacketBuffer.h
index bfe293b2..37d8b09c 100644
--- a/src/PacketBuffer.h
+++ b/src/PacketBuffer.h
@@ -28,6 +28,12 @@
 
 namespace QtAV {
 
+/*
+ * take empty: start buffering, block at next take if still empty
+ * take enough: start to put more packets
+ * put enough: end buffering, end take block
+ * put full: stop putting more packets
+ */
 class PacketBuffer : BlockingQueue<Packet, QQueue>
 {
 public:
@@ -55,13 +61,15 @@ public:
      * Current buffered value in the queue
      */
     int buffered() const;
+    bool isBuffering() const;
     /*!
      * \brief bufferProgress
      * How much of the data buffer is currently filled, from 0.0 (empty) to 1.0 (enough or full).
-     * bufferProgress() == 1
+     * bufferProgress() can be less than 1 if not isBuffering();
      * \return Percent of buffered time, bytes or packets.
      */
     qreal bufferProgress() const;
+    qreal bufferSpeed() const;
 
 protected:
     bool checkEnough() const Q_DECL_OVERRIDE;
@@ -70,6 +78,7 @@ protected:
     void onPut(const Packet &) Q_DECL_OVERRIDE;
 private:
     BufferMode m_mode;
+    bool m_buffering;
     // bytes or count
     quint32 m_buffer;
     qint32 m_value0, m_value1;