chromecast/media/cma/backend/media_clock_device.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 CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_
   6 #define CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/macros.h"
  12 #include "base/threading/non_thread_safe.h"
  13 #include "base/time/time.h"
  14
  15 namespace chromecast {
  16 namespace media {
  17
  18 // MediaClockDevice -
  19 //
  20 // State machine:
  21 //                      -------------------
  22 //                      |                 |
  23 //                      v                 |
  24 // kUninitialized --> kIdle  --------- kRunning
  25 //
  26 // {any state} --> kError
  27 //
  28 // Notes:
  29 // - Hardware resources are acquired when transitioning from the
  30 //   |kUninitialized| state to the |kIdle| state.
  31 // - The initial value of the timeline can only be set in the kIdle state.
  32 //
  33 class MediaClockDevice
  34     : NON_EXPORTED_BASE(public base::NonThreadSafe) {
  35  public:
  36   enum State {
  37     kStateUninitialized,
  38     kStateIdle,
  39     kStateRunning,
  40     kStateError,
  41   };
  42
  43   // Return true if transition from |state1| to |state2| is a valid state
  44   // transition.
  45   static bool IsValidStateTransition(State state1, State state2);
  46
  47   // Returns string representation of state (for logging)
  48   static std::string StateToString(const State& state);
  49
  50   MediaClockDevice();
  51   virtual ~MediaClockDevice();
  52
  53   // Return the current state of the media clock.
  54   virtual State GetState() const = 0;
  55
  56   // Changes the state and performs any necessary transitions.
  57   // Returns true when successful.
  58   virtual bool SetState(State new_state) = 0;
  59
  60   // Sets the initial value of the timeline.
  61   // Can only be invoked in state kStateIdle.
  62   // Returns true when successful.
  63   virtual bool ResetTimeline(base::TimeDelta time) = 0;
  64
  65   // Sets the clock rate.
  66   // Setting it to 0 means the clock is not progressing and that the renderer
  67   // tied to this media clock should pause rendering.
  68   // Can only be invoked in states kStateIdle or kStateRunning.
  69   virtual bool SetRate(float rate) = 0;
  70
  71   // Retrieves the media clock time.
  72   // Can only be invoked in states kStateIdle or kStateRunning.
  73   virtual base::TimeDelta GetTime() = 0;
  74
  75  private:
  76   DISALLOW_COPY_AND_ASSIGN(MediaClockDevice);
  77 };
  78
  79 }  // namespace media
  80 }  // namespace chromecast
  81
  82 #endif  // CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_