Make the timestamp unroll offset consistent accross PES pids.

media/formats/mp2t/timestamp_unroller.h

Index: media/formats/mp2t/timestamp_unroller.h
diff --git a/media/formats/mp2t/timestamp_unroller.h b/media/formats/mp2t/timestamp_unroller.h
new file mode 100644
index 0000000000000000000000000000000000000000..9f372ff799260d5596c5f83ff445cd1dce28174a
--- /dev/null
+++ b/media/formats/mp2t/timestamp_unroller.h
@@ -0,0 +1,54 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MEDIA_FORMATS_MP2T_TIMESTAMP_UNROLLER_H_
+#define MEDIA_FORMATS_MP2T_TIMESTAMP_UNROLLER_H_
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "media/base/media_export.h"
+
+namespace media {
+namespace mp2t {
+
+class MEDIA_EXPORT TimestampUnroller {
+ public:
+  TimestampUnroller();
+  ~TimestampUnroller();
+
+  // Given that |timestamp| is coded using 33 bits (accuracy of MPEG-2 TS
+  // timestamps), GetUnrolledTimestamp returns the corresponding unrolled
+  // timestamp.
+  // The unrolled timestamp is defined by:
+  // |timestamp| + k * (2 ^ 33)
+  // where k is estimated so that the unrolled timestamp is as close as
+  // possible to the previous unrolled timestamp returned by this function
+  // (if this function has not been called before, it will return the timestamp
+  // unmodified).
+  int64 GetUnrolledTimestamp(int64 timestamp);
+
+  // Return the minimum unrolled timestamp seen so far.
+  int64 GetMinUnrolledTimestamp() const {
+    return min_unrolled_timestamp_;
+  }
+
+  // Reset the TimestampUnroller to its initial state.
+  void Reset();
+
+ private:
+  // Indicate whether the value of |previous_unrolled_timestamp_| is valid.
+  bool is_previous_timestamp_valid_;
+
+  // This is the last output of GetUnrolledTimestamp.
+  int64 previous_unrolled_timestamp_;
+
+  int64 min_unrolled_timestamp_;
+
+  DISALLOW_COPY_AND_ASSIGN(TimestampUnroller);
+};
+
+}  // namespace mp2t
+}  // namespace media
+
+#endif  // MEDIA_FORMATS_MP2T_TIMESTAMP_UNROLLER_H_