Move the capture ntp computing code to ntp_calculator so that later it can be shared with voe.

BUG=3111
TEST=try bots
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/13489004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6152 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/rtp_rtcp/interface/remote_ntp_time_estimator.h

@@ -0,0 +1,50 @@
+/*
+ *  Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_RTP_RTCP_INTERFACE_REMOTE_NTP_TIME_ESTIMATOR_H_
+#define WEBRTC_MODULES_RTP_RTCP_INTERFACE_REMOTE_NTP_TIME_ESTIMATOR_H_
+
+#include "webrtc/system_wrappers/interface/rtp_to_ntp.h"
+#include "webrtc/system_wrappers/interface/scoped_ptr.h"
+
+namespace webrtc {
+
+class Clock;
+class RtpRtcp;
+class TimestampExtrapolator;
+
+// RemoteNtpTimeEstimator can be used to estimate a given RTP timestamp's NTP
+// time in local timebase.
+// Note that it needs to be trained with at least 2 RTCP SR (by calling
+// |UpdateRtcpTimestamp|) before it can be used.
+class RemoteNtpTimeEstimator {
+ public:
+  explicit RemoteNtpTimeEstimator(Clock* clock);
+
+  ~RemoteNtpTimeEstimator();
+
+  // Updates the estimator with the timestamp from newly received RTCP SR for
+  // |ssrc|. The RTCP SR is read from |rtp_rtcp|.
+  bool UpdateRtcpTimestamp(uint32_t ssrc, RtpRtcp* rtp_rtcp);
+
+  // Estimates the NTP timestamp in local timebase from |rtp_timestamp|.
+  // Returns the NTP timestamp in ms when success. -1 if failed.
+  int64_t Estimate(uint32_t rtp_timestamp);
+
+ private:
+  Clock* clock_;
+  scoped_ptr<TimestampExtrapolator> ts_extrapolator_;
+  RtcpList rtcp_list_;
+  DISALLOW_COPY_AND_ASSIGN(RemoteNtpTimeEstimator);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_RTP_RTCP_INTERFACE_REMOTE_NTP_TIME_ESTIMATOR_H_