Implement timestamp translation/filter in VideoCapturer.

webrtc/media/base/videocapturer.h

Index: webrtc/media/base/videocapturer.h
diff --git a/webrtc/media/base/videocapturer.h b/webrtc/media/base/videocapturer.h
index 329ba086b90dfe1139c6f83cdd41b291af38540f..f947eda1164691d8c9c2cfa5bcc6f7b73b0486d5 100644
--- a/webrtc/media/base/videocapturer.h
+++ b/webrtc/media/base/videocapturer.h
@@ -225,15 +225,20 @@ class VideoCapturer : public sigslot::has_slots<>,
   // Reports the appropriate frame size after adaptation. Returns true
   // if a frame is wanted. Returns false if there are no interested
   // sinks, or if the VideoAdapter decides to drop the frame.
+  // |capture_time_ns| is the camera's timestamp, using an arbitrary
+  // offset and possibly slightly off frequency. |time_us| is the
+  // timestamp translated into the same scale as rtc::TimeMicros.

[stefan-webrtc, 2016/06/08 11:28:42]

Comment on system_time_us to make it clear that it should correspond to the
system time of the capture.

[nisse-webrtc, 2016/06/09 10:02:58]

I've expanded the comments here.

   bool AdaptFrame(int width,
                   int height,
-                  int64_t capture_time_ns,
+                  int64_t capture_time_us,
+                  int64_t system_time_us,
                   int* out_width,
                   int* out_height,
                   int* crop_width,
                   int* crop_height,
                   int* crop_x,
-                  int* crop_y);
+                  int* crop_y,
+                  int64_t* time_us);
 
   // Callback attached to SignalFrameCaptured where SignalVideoFrames is called.
   void OnFrameCaptured(VideoCapturer* video_capturer,
@@ -284,6 +289,9 @@ class VideoCapturer : public sigslot::has_slots<>,
 
   void UpdateInputSize(int width, int height);
 
+  // Update the estimated offset between camera time and system monotonic time.
+  void UpdateOffset(int64_t camera_time_us, int64_t system_time_us);
+
   rtc::ThreadChecker thread_checker_;
   std::string id_;
   CaptureState capture_state_;
@@ -310,6 +318,11 @@ class VideoCapturer : public sigslot::has_slots<>,
   // Whether capturer should apply rotation to the frame before signaling it.
   bool apply_rotation_;
 
+  // State for the timestamp translation.
+  unsigned frames_seen_;

[stefan-webrtc, 2016/06/08 11:28:42]

int

[nisse-webrtc, 2016/06/09 10:02:58]

Done.

+  // Estimated offset between camera time and system monotonic time.
+  int64_t offset_us_;
+
   RTC_DISALLOW_COPY_AND_ASSIGN(VideoCapturer);
 };