media/formats/mp2t/timestamp_unroller.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_FORMATS_MP2T_TIMESTAMP_UNROLLER_H_
   6 #define MEDIA_FORMATS_MP2T_TIMESTAMP_UNROLLER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/macros.h"
  10 #include "media/base/media_export.h"
  11
  12 namespace media {
  13 namespace mp2t {
  14
  15 class MEDIA_EXPORT TimestampUnroller {
  16  public:
  17   TimestampUnroller();
  18   ~TimestampUnroller();
  19
  20   // Given that |timestamp| is coded using 33 bits (accuracy of MPEG-2 TS
  21   // timestamps), GetUnrolledTimestamp returns the corresponding unrolled
  22   // timestamp.
  23   // The unrolled timestamp is defined by:
  24   // |timestamp| + k * (2 ^ 33)
  25   // where k is estimated so that the unrolled timestamp is as close as
  26   // possible to the previous unrolled timestamp returned by this function
  27   // (if this function has not been called before, it will return the timestamp
  28   // unmodified).
  29   int64 GetUnrolledTimestamp(int64 timestamp);
  30
  31   // Reset the TimestampUnroller to its initial state.
  32   void Reset();
  33
  34  private:
  35   // Indicate whether the value of |previous_unrolled_timestamp_| is valid.
  36   bool is_previous_timestamp_valid_;
  37
  38   // This is the last output of GetUnrolledTimestamp.
  39   int64 previous_unrolled_timestamp_;
  40
  41   DISALLOW_COPY_AND_ASSIGN(TimestampUnroller);
  42 };
  43
  44 }  // namespace mp2t
  45 }  // namespace media
  46
  47 #endif  // MEDIA_FORMATS_MP2T_TIMESTAMP_UNROLLER_H_