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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.mozilla.thirdparty.com.google.android.exoplayer2.util;
import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
/**
* Offsets timestamps according to an initial sample timestamp offset. MPEG-2 TS timestamps scaling
* and adjustment is supported, taking into account timestamp rollover.
*/
public final class TimestampAdjuster {
/**
* A special {@code firstSampleTimestampUs} value indicating that presentation timestamps should
* not be offset.
*/
public static final long DO_NOT_OFFSET = Long.MAX_VALUE;
/**
* The value one greater than the largest representable (33 bit) MPEG-2 TS 90 kHz clock
* presentation timestamp.
*/
private static final long MAX_PTS_PLUS_ONE = 0x200000000L;
private long firstSampleTimestampUs;
private long timestampOffsetUs;
// Volatile to allow isInitialized to be called on a different thread to adjustSampleTimestamp.
private volatile long lastSampleTimestampUs;
/**
* @param firstSampleTimestampUs See {@link #setFirstSampleTimestampUs(long)}.
*/
public TimestampAdjuster(long firstSampleTimestampUs) {
lastSampleTimestampUs = C.TIME_UNSET;
setFirstSampleTimestampUs(firstSampleTimestampUs);
}
/**
* Sets the desired result of the first call to {@link #adjustSampleTimestamp(long)}. Can only be
* called before any timestamps have been adjusted.
*
* @param firstSampleTimestampUs The first adjusted sample timestamp in microseconds, or
* {@link #DO_NOT_OFFSET} if presentation timestamps should not be offset.
*/
public synchronized void setFirstSampleTimestampUs(long firstSampleTimestampUs) {
Assertions.checkState(lastSampleTimestampUs == C.TIME_UNSET);
this.firstSampleTimestampUs = firstSampleTimestampUs;
}
/** Returns the last value passed to {@link #setFirstSampleTimestampUs(long)}. */
public long getFirstSampleTimestampUs() {
return firstSampleTimestampUs;
}
/**
* Returns the last value obtained from {@link #adjustSampleTimestamp}. If {@link
* #adjustSampleTimestamp} has not been called, returns the result of calling {@link
* #getFirstSampleTimestampUs()}. If this value is {@link #DO_NOT_OFFSET}, returns {@link
* C#TIME_UNSET}.
*/
public long getLastAdjustedTimestampUs() {
return lastSampleTimestampUs != C.TIME_UNSET
? (lastSampleTimestampUs + timestampOffsetUs)
: firstSampleTimestampUs != DO_NOT_OFFSET ? firstSampleTimestampUs : C.TIME_UNSET;
}
/**
* Returns the offset between the input of {@link #adjustSampleTimestamp(long)} and its output.
* If {@link #DO_NOT_OFFSET} was provided to the constructor, 0 is returned. If the timestamp
* adjuster is yet not initialized, {@link C#TIME_UNSET} is returned.
*
* @return The offset between {@link #adjustSampleTimestamp(long)}'s input and output.
* {@link C#TIME_UNSET} if the adjuster is not yet initialized and 0 if timestamps should not
* be offset.
*/
public long getTimestampOffsetUs() {
return firstSampleTimestampUs == DO_NOT_OFFSET
? 0
: lastSampleTimestampUs == C.TIME_UNSET ? C.TIME_UNSET : timestampOffsetUs;
}
/**
* Resets the instance to its initial state.
*/
public void reset() {
lastSampleTimestampUs = C.TIME_UNSET;
}
/**
* Scales and offsets an MPEG-2 TS presentation timestamp considering wraparound.
*
* @param pts90Khz A 90 kHz clock MPEG-2 TS presentation timestamp.
* @return The adjusted timestamp in microseconds.
*/
public long adjustTsTimestamp(long pts90Khz) {
if (pts90Khz == C.TIME_UNSET) {
return C.TIME_UNSET;
}
if (lastSampleTimestampUs != C.TIME_UNSET) {
// The wrap count for the current PTS may be closestWrapCount or (closestWrapCount - 1),
// and we need to snap to the one closest to lastSampleTimestampUs.
long lastPts = usToPts(lastSampleTimestampUs);
long closestWrapCount = (lastPts + (MAX_PTS_PLUS_ONE / 2)) / MAX_PTS_PLUS_ONE;
long ptsWrapBelow = pts90Khz + (MAX_PTS_PLUS_ONE * (closestWrapCount - 1));
long ptsWrapAbove = pts90Khz + (MAX_PTS_PLUS_ONE * closestWrapCount);
pts90Khz =
Math.abs(ptsWrapBelow - lastPts) < Math.abs(ptsWrapAbove - lastPts)
? ptsWrapBelow
: ptsWrapAbove;
}
return adjustSampleTimestamp(ptsToUs(pts90Khz));
}
/**
* Offsets a timestamp in microseconds.
*
* @param timeUs The timestamp to adjust in microseconds.
* @return The adjusted timestamp in microseconds.
*/
public long adjustSampleTimestamp(long timeUs) {
if (timeUs == C.TIME_UNSET) {
return C.TIME_UNSET;
}
// Record the adjusted PTS to adjust for wraparound next time.
if (lastSampleTimestampUs != C.TIME_UNSET) {
lastSampleTimestampUs = timeUs;
} else {
if (firstSampleTimestampUs != DO_NOT_OFFSET) {
// Calculate the timestamp offset.
timestampOffsetUs = firstSampleTimestampUs - timeUs;
}
synchronized (this) {
lastSampleTimestampUs = timeUs;
// Notify threads waiting for this adjuster to be initialized.
notifyAll();
}
}
return timeUs + timestampOffsetUs;
}
/**
* Blocks the calling thread until this adjuster is initialized.
*
* @throws InterruptedException If the thread was interrupted.
*/
public synchronized void waitUntilInitialized() throws InterruptedException {
while (lastSampleTimestampUs == C.TIME_UNSET) {
wait();
}
}
/**
* Converts a 90 kHz clock timestamp to a timestamp in microseconds.
*
* @param pts A 90 kHz clock timestamp.
* @return The corresponding value in microseconds.
*/
public static long ptsToUs(long pts) {
return (pts * C.MICROS_PER_SECOND) / 90000;
}
/**
* Converts a timestamp in microseconds to a 90 kHz clock timestamp.
*
* @param us A value in microseconds.
* @return The corresponding value as a 90 kHz clock timestamp.
*/
public static long usToPts(long us) {
return (us * 90000) / C.MICROS_PER_SECOND;
}
}
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