New method TimestampAligner::TranslateTimestamp

webrtc/base/timestampaligner.h

 /*
  *  Copyright (c) 2016 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_BASE_TIMESTAMPALIGNER_H_
 #define WEBRTC_BASE_TIMESTAMPALIGNER_H_
 
 #include "webrtc/base/basictypes.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/optional.h"
 
 namespace rtc {
 
 // This class is not thread safe, so all calls to it must be synchronized
 // externally.
 class TimestampAligner {

[perkj_webrtc, 2016/09/08 07:25:23]

Can you add a comment about how to use this. 

And maybe- make the UpdateOffset and ClipTimestamp protected for testing and
create new public helper method that give you the timestamp that should be used
by a frame.

[nisse-webrtc, 2016/09/08 08:14:09]

Regardless of my other comment, I agree it makes sense with an all-in-one
function, which could be called TranslateTimestamp.

  public:
   TimestampAligner();
   ~TimestampAligner();
 
  public:
   // Update the estimated offset between camera time and system monotonic time.
   int64_t UpdateOffset(int64_t camera_time_us, int64_t system_time_us);
 
+  // Clip timestamp, it should larger than the previous timestamp but

[perkj_webrtc, 2016/09/08 07:25:23]

please clarify this sentence.

change should to to will be? 

[nisse-webrtc, 2016/09/08 08:14:09]

Done.

+  // no larger than current system time.
   int64_t ClipTimestamp(int64_t filtered_time_us, int64_t system_time_us);
 
  private:
   // State for the timestamp translation.
   int frames_seen_;
   // Estimated offset between camera time and system monotonic time.
   int64_t offset_us_;
 
   // State for timestamp clipping, applied after the filter, to ensure
   // that translated timestamps are monotonic and not in the future.
   // Subtracted from the translated timestamps.
   int64_t clip_bias_us_;
   rtc::Optional<int64_t> prev_translated_time_us_;
   RTC_DISALLOW_COPY_AND_ASSIGN(TimestampAligner);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_TIMESTAMPALIGNER_H_