Chromecast: adds interfaces for hardware layer of CMA pipeline.

chromecast/media/cma/backend/media_clock_device.h

+// 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 CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_
+#define CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/macros.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/time/time.h"
+
+namespace chromecast {
+namespace media {
+
+// MediaClockDevice -
+//
+// State machine:
+//                      -------------------
+//                      |                 |
+//                      v                 |
+// kUninitialized --> kIdle  --------- kRunning
+//
+// {any state} --> kError
+//
+// Notes:
+// - Hardware resources are acquired when transitioning from the
+//   |kUninitialized| state to the |kIdle| state.
+// - The initial value of the timeline can only be set in the kIdle state.
+//
+class MediaClockDevice
+    : NON_EXPORTED_BASE(public base::NonThreadSafe) {
+ public:
+  enum State {
+    kStateUninitialized,
+    kStateIdle,
+    kStateRunning,
+    kStateError,
+  };
+
+  // Return true if transition from |state1| to |state2| is a valid state
+  // transition.
+  static bool IsValidStateTransition(State state1, State state2);
+
+  // Returns string representation of state (for logging)
+  static std::string StateToString(const State& state);
+
+  MediaClockDevice();
+  virtual ~MediaClockDevice();
+
+  // Return the current state of the media clock.
+  virtual State GetState() const = 0;
+
+  // Changes the state and performs any necessary transitions.
+  // Returns true when successful.
+  virtual bool SetState(State new_state) = 0;
+
+  // Sets the initial value of the timeline.
+  // Can only be invoked in state kStateIdle.
+  // Returns true when successful.
+  virtual bool ResetTimeline(base::TimeDelta time) = 0;
+
+  // Sets the clock rate.
+  // Setting it to 0 means the clock is not progressing and that the renderer
+  // tied to this media clock should pause rendering.
+  // Can only be invoked in states kStateIdle or kStateRunning.
+  virtual bool SetRate(float rate) = 0;
+
+  // Retrieves the media clock time.
+  // Can only be invoked in states kStateIdle or kStateRunning.
+  virtual base::TimeDelta GetTime() = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MediaClockDevice);
+};
+
+}  // namespace media
+}  // namespace chromecast
+
+#endif  // CHROMECAST_MEDIA_CMA_BACKEND_MEDIA_CLOCK_DEVICE_H_