1 files changed, 59 insertions, 0 deletions
diff --git a/third_party/libwebrtc/sdk/android/api/org/webrtc/TimestampAligner.java b/third_party/libwebrtc/sdk/android/api/org/webrtc/TimestampAligner.java
new file mode 100644
index 0000000000..d96c939595
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+++ b/third_party/libwebrtc/sdk/android/api/org/webrtc/TimestampAligner.java
@@ -0,0 +1,59 @@
+/*
+ *  Copyright 2018 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.
+ */
+
+package org.webrtc;
+
+/**
+ * The TimestampAligner class helps translating camera timestamps into the same timescale as is
+ * used by rtc::TimeNanos(). Some cameras have built in timestamping which is more accurate than
+ * reading the system clock, but using a different epoch and unknown clock drift. Frame timestamps
+ * in webrtc should use rtc::TimeNanos (system monotonic time), and this class provides a filter
+ * which lets us use the rtc::TimeNanos timescale, and at the same time take advantage of higher
+ * accuracy of the camera clock. This class is a wrapper on top of rtc::TimestampAligner.
+ */
+public class TimestampAligner {
+  /**
+   * Wrapper around rtc::TimeNanos(). This is normally same as System.nanoTime(), but call this
+   * function to be safe.
+   */
+  public static long getRtcTimeNanos() {
+    return nativeRtcTimeNanos();
+  }
+
+  private volatile long nativeTimestampAligner = nativeCreateTimestampAligner();
+
+  /**
+   * Translates camera timestamps to the same timescale as is used by rtc::TimeNanos().
+   * `cameraTimeNs` is assumed to be accurate, but with an unknown epoch and clock drift. Returns
+   * the translated timestamp.
+   */
+  public long translateTimestamp(long cameraTimeNs) {
+    checkNativeAlignerExists();
+    return nativeTranslateTimestamp(nativeTimestampAligner, cameraTimeNs);
+  }
+
+  /** Dispose native timestamp aligner. */
+  public void dispose() {
+    checkNativeAlignerExists();
+    nativeReleaseTimestampAligner(nativeTimestampAligner);
+    nativeTimestampAligner = 0;
+  }
+
+  private void checkNativeAlignerExists() {
+    if (nativeTimestampAligner == 0) {
+      throw new IllegalStateException("TimestampAligner has been disposed.");
+    }
+  }
+
+  private static native long nativeRtcTimeNanos();
+  private static native long nativeCreateTimestampAligner();
+  private static native void nativeReleaseTimestampAligner(long timestampAligner);
+  private static native long nativeTranslateTimestamp(long timestampAligner, long cameraTimeNs);
+}