Checking in media::Synchronizer, a utility class to facilitate A/V synchronization.

Review URL: http://codereview.chromium.org/19693

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8950 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 59 insertions, 0 deletions

diff --git a/media/base/synchronizer.h b/media/base/synchronizer.h
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+++ b/media/base/synchronizer.h
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+// Copyright (c) 2009 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.
+
+// Utility class for video renderers to help synchronize against a reference
+// clock while also taking rendering duration into account.
+//
+// Video renderers should maintain an instance of this object for the entire
+// lifetime since Synchronizer maintains internal state to improve playback.
+//
+// VideoRenderer usage is as follows:
+//   Receive a new frame from the decoder
+//   Call StartRendering
+//   Perform colour space conversion and render the frame
+//   Call StopRendering
+//   Call CalculateDelay passing in the rendered frame and optional next frame
+//   Issue delayed task or sleep on thread for returned amount of time
+
+#ifndef MEDIA_BASE_SYNCHRONIZER_H_
+#define MEDIA_BASE_SYNCHRONIZER_H_
+
+#include "base/basictypes.h"
+#include "base/time.h"
+#include "media/base/buffers.h"
+
+namespace media {
+
+class Synchronizer {
+ public:
+  Synchronizer();
+  ~Synchronizer();
+
+  // Starts the rendering timer.
+  void StartRendering();
+
+  // Stops the rendering timer.
+  void StopRendering();
+
+  // Calculates the appropriate amount of delay in microseconds given the
+  // current time, the current sample and the next sample (may be NULL,
+  // but is recommended to pass in for smoother playback).
+  void CalculateDelay(base::TimeDelta time, const StreamSample* now,
+                      const StreamSample* next, base::TimeDelta* delay_out,
+                      bool* should_skip_out);
+
+ private:
+  static const int64 kMinFrameDelayUs;
+  static const int64 kMaxFrameDelayUs;
+
+  base::TimeTicks rendering_start_;
+  base::TimeTicks rendering_stop_;
+  base::TimeDelta last_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(Synchronizer);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_SYNCHRONIZER_H_