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/*
* 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);
}
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