60 lines
2.3 KiB
Java
60 lines
2.3 KiB
Java
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/*
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* Copyright 2018 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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package org.webrtc;
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/**
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* The TimestampAligner class helps translating camera timestamps into the same timescale as is
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* used by rtc::TimeNanos(). Some cameras have built in timestamping which is more accurate than
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* reading the system clock, but using a different epoch and unknown clock drift. Frame timestamps
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* in webrtc should use rtc::TimeNanos (system monotonic time), and this class provides a filter
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* which lets us use the rtc::TimeNanos timescale, and at the same time take advantage of higher
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* accuracy of the camera clock. This class is a wrapper on top of rtc::TimestampAligner.
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*/
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public class TimestampAligner {
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/**
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* Wrapper around rtc::TimeNanos(). This is normally same as System.nanoTime(), but call this
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* function to be safe.
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*/
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public static long getRtcTimeNanos() {
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return nativeRtcTimeNanos();
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}
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private volatile long nativeTimestampAligner = nativeCreateTimestampAligner();
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/**
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* Translates camera timestamps to the same timescale as is used by rtc::TimeNanos().
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* |cameraTimeNs| is assumed to be accurate, but with an unknown epoch and clock drift. Returns
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* the translated timestamp.
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*/
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public long translateTimestamp(long cameraTimeNs) {
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checkNativeAlignerExists();
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return nativeTranslateTimestamp(nativeTimestampAligner, cameraTimeNs);
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}
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/** Dispose native timestamp aligner. */
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public void dispose() {
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checkNativeAlignerExists();
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nativeReleaseTimestampAligner(nativeTimestampAligner);
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nativeTimestampAligner = 0;
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}
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private void checkNativeAlignerExists() {
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if (nativeTimestampAligner == 0) {
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throw new IllegalStateException("TimestampAligner has been disposed.");
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}
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}
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private static native long nativeRtcTimeNanos();
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private static native long nativeCreateTimestampAligner();
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private static native void nativeReleaseTimestampAligner(long timestampAligner);
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private static native long nativeTranslateTimestamp(long timestampAligner, long cameraTimeNs);
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}
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