chromecast/public/media/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_PUBLIC_MEDIA_MEDIA_CLOCK_DEVICE_H_
   6 #define CHROMECAST_PUBLIC_MEDIA_MEDIA_CLOCK_DEVICE_H_
   7
   8 #include <string>
   9
  10 namespace chromecast {
  11 namespace media {
  12
  13 // Interface for platform-specific pipeline clock.
  14 // Pipeline clocks follow this state machine:
  15 //                      -------------------
  16 //                      |                 |
  17 //                      v                 |
  18 // kUninitialized --> kIdle  --------- kRunning
  19 //
  20 // {any state} --> kError
  21 //
  22 // Notes:
  23 // - Hardware resources should be acquired when transitioning from the
  24 //   |kUninitialized| state to the |kIdle| state.
  25 // - The initial value of the timeline will only be set in the kIdle state.
  26 class MediaClockDevice {
  27  public:
  28   enum State {
  29     kStateUninitialized,
  30     kStateIdle,
  31     kStateRunning,
  32     kStateError,
  33   };
  34
  35   virtual ~MediaClockDevice() {}
  36
  37   // Returns the current state of the media clock.
  38   virtual State GetState() const = 0;
  39
  40   // Changes the state and performs any necessary transitions.
  41   // Returns true when successful.
  42   virtual bool SetState(State new_state) = 0;
  43
  44   // Sets the initial value of the timeline in microseconds.
  45   // Will only be invoked in state kStateIdle.
  46   // Returns true when successful.
  47   virtual bool ResetTimeline(int64_t time_microseconds) = 0;
  48
  49   // Sets the clock rate.
  50   // |rate| == 0 means the clock is not progressing and that the renderer
  51   // tied to this media clock should pause rendering.
  52   // Will only be invoked in states kStateIdle or kStateRunning.
  53   virtual bool SetRate(float rate) = 0;
  54
  55   // Retrieves the media clock time in microseconds.
  56   // Will only be invoked in states kStateIdle or kStateRunning.
  57   virtual int64_t GetTimeMicroseconds() = 0;
  58 };
  59
  60 }  // namespace media
  61 }  // namespace chromecast
  62
  63 #endif  // CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_