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Add option to MergingMediaSource to adjust for period time diffs
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Without this option it's impossible to merge periods covering
different timestamps (at least not without playback issues).

Issue:issue:#6103
PiperOrigin-RevId: 299817540
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@tonihei @ojw28
tonihei authored and ojw28 committed Mar 10, 2020
1 parent 041a069 commit 0a89d0e
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Showing 4 changed files with 482 additions and 35 deletions.
3 changes: 3 additions & 0 deletions RELEASENOTES.md
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Expand Up @@ -47,6 +47,9 @@
([#2863](https://github.com/google/ExoPlayer/issues/2863)).
* Add optional automatic `WifiLock` handling to `SimpleExoPlayer`
([#6914](https://github.com/google/ExoPlayer/issues/6914)).
* Add option to `MergingMediaSource` to adjust the time offsets between
the merged sources
([#6103](https://github.com/google/ExoPlayer/issues/6103)).
* Text:
* Parse `<ruby>` and `<rt>` tags in WebVTT subtitles (rendering is coming
later).
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232 changes: 216 additions & 16 deletions library/core/src/main/java/com/google/android/exoplayer2/source/MergingMediaPeriod.java
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Expand Up @@ -17,22 +17,26 @@

import androidx.annotation.Nullable;
import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.FormatHolder;
import com.google.android.exoplayer2.SeekParameters;
import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
import com.google.android.exoplayer2.offline.StreamKey;
import com.google.android.exoplayer2.trackselection.TrackSelection;
import com.google.android.exoplayer2.util.Assertions;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.List;
import org.checkerframework.checker.nullness.compatqual.NullableType;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;

/**
* Merges multiple {@link MediaPeriod}s.
*/
/* package */ final class MergingMediaPeriod implements MediaPeriod, MediaPeriod.Callback {

public final MediaPeriod[] periods;

private final MediaPeriod[] periods;
private final IdentityHashMap<SampleStream, Integer> streamPeriodIndices;
private final CompositeSequenceableLoaderFactory compositeSequenceableLoaderFactory;
private final ArrayList<MediaPeriod> childrenPendingPreparation;
Expand All @@ -42,7 +46,9 @@
private MediaPeriod[] enabledPeriods;
private SequenceableLoader compositeSequenceableLoader;

public MergingMediaPeriod(CompositeSequenceableLoaderFactory compositeSequenceableLoaderFactory,
public MergingMediaPeriod(
CompositeSequenceableLoaderFactory compositeSequenceableLoaderFactory,
long[] periodTimeOffsetsUs,
MediaPeriod... periods) {
this.compositeSequenceableLoaderFactory = compositeSequenceableLoaderFactory;
this.periods = periods;
Expand All @@ -51,6 +57,22 @@ public MergingMediaPeriod(CompositeSequenceableLoaderFactory compositeSequenceab
compositeSequenceableLoaderFactory.createCompositeSequenceableLoader();
streamPeriodIndices = new IdentityHashMap<>();
enabledPeriods = new MediaPeriod[0];
for (int i = 0; i < periods.length; i++) {
if (periodTimeOffsetsUs[i] != 0) {
this.periods[i] = new TimeOffsetMediaPeriod(periods[i], periodTimeOffsetsUs[i]);
}
}
}

/**
* Returns the child period passed to {@link
* #MergingMediaPeriod(CompositeSequenceableLoaderFactory, long[], MediaPeriod...)} at the
* specified index.
*/
public MediaPeriod getChildPeriod(int index) {
return periods[index] instanceof TimeOffsetMediaPeriod
? ((TimeOffsetMediaPeriod) periods[index]).mediaPeriod
: periods[index];
}

@Override
Expand Down Expand Up @@ -181,23 +203,32 @@ public long getNextLoadPositionUs() {

@Override
public long readDiscontinuity() {
long positionUs = periods[0].readDiscontinuity();
// Periods other than the first one are not allowed to report discontinuities.
for (int i = 1; i < periods.length; i++) {
if (periods[i].readDiscontinuity() != C.TIME_UNSET) {
throw new IllegalStateException("Child reported discontinuity.");
}
}
// It must be possible to seek enabled periods to the new position, if there is one.
if (positionUs != C.TIME_UNSET) {
for (MediaPeriod enabledPeriod : enabledPeriods) {
if (enabledPeriod != periods[0]
&& enabledPeriod.seekToUs(positionUs) != positionUs) {
long discontinuityUs = C.TIME_UNSET;
for (MediaPeriod period : enabledPeriods) {
long otherDiscontinuityUs = period.readDiscontinuity();
if (otherDiscontinuityUs != C.TIME_UNSET) {
if (discontinuityUs == C.TIME_UNSET) {
discontinuityUs = otherDiscontinuityUs;
// First reported discontinuity. Seek all previous periods to the new position.
for (MediaPeriod previousPeriod : enabledPeriods) {
if (previousPeriod == period) {
break;
}
if (previousPeriod.seekToUs(discontinuityUs) != discontinuityUs) {
throw new IllegalStateException("Unexpected child seekToUs result.");
}
}
} else if (otherDiscontinuityUs != discontinuityUs) {
throw new IllegalStateException("Conflicting discontinuities.");
}
} else if (discontinuityUs != C.TIME_UNSET) {
// We already have a discontinuity, seek this period to the new position.
if (period.seekToUs(discontinuityUs) != discontinuityUs) {
throw new IllegalStateException("Unexpected child seekToUs result.");
}
}
}
return positionUs;
return discontinuityUs;
}

@Override
Expand Down Expand Up @@ -253,4 +284,173 @@ public void onContinueLoadingRequested(MediaPeriod ignored) {
Assertions.checkNotNull(callback).onContinueLoadingRequested(this);
}

private static final class TimeOffsetMediaPeriod implements MediaPeriod, MediaPeriod.Callback {

private final MediaPeriod mediaPeriod;
private final long timeOffsetUs;

private @MonotonicNonNull Callback callback;

public TimeOffsetMediaPeriod(MediaPeriod mediaPeriod, long timeOffsetUs) {
this.mediaPeriod = mediaPeriod;
this.timeOffsetUs = timeOffsetUs;
}

@Override
public void prepare(Callback callback, long positionUs) {
this.callback = callback;
mediaPeriod.prepare(/* callback= */ this, positionUs - timeOffsetUs);
}

@Override
public void maybeThrowPrepareError() throws IOException {
mediaPeriod.maybeThrowPrepareError();
}

@Override
public TrackGroupArray getTrackGroups() {
return mediaPeriod.getTrackGroups();
}

@Override
public List<StreamKey> getStreamKeys(List<TrackSelection> trackSelections) {
return mediaPeriod.getStreamKeys(trackSelections);
}

@Override
public long selectTracks(
@NullableType TrackSelection[] selections,
boolean[] mayRetainStreamFlags,
@NullableType SampleStream[] streams,
boolean[] streamResetFlags,
long positionUs) {
@NullableType SampleStream[] childStreams = new SampleStream[streams.length];
for (int i = 0; i < streams.length; i++) {
TimeOffsetSampleStream sampleStream = (TimeOffsetSampleStream) streams[i];
childStreams[i] = sampleStream != null ? sampleStream.getChildStream() : null;
}
long startPositionUs =
mediaPeriod.selectTracks(
selections,
mayRetainStreamFlags,
childStreams,
streamResetFlags,
positionUs - timeOffsetUs);
for (int i = 0; i < streams.length; i++) {
@Nullable SampleStream childStream = childStreams[i];
if (childStream == null) {
streams[i] = null;
} else if (streams[i] == null
|| ((TimeOffsetSampleStream) streams[i]).getChildStream() != childStream) {
streams[i] = new TimeOffsetSampleStream(childStream, timeOffsetUs);
}
}
return startPositionUs + timeOffsetUs;
}

@Override
public void discardBuffer(long positionUs, boolean toKeyframe) {
mediaPeriod.discardBuffer(positionUs - timeOffsetUs, toKeyframe);
}

@Override
public long readDiscontinuity() {
long discontinuityPositionUs = mediaPeriod.readDiscontinuity();
return discontinuityPositionUs == C.TIME_UNSET
? C.TIME_UNSET
: discontinuityPositionUs + timeOffsetUs;
}

@Override
public long seekToUs(long positionUs) {
return mediaPeriod.seekToUs(positionUs - timeOffsetUs) + timeOffsetUs;
}

@Override
public long getAdjustedSeekPositionUs(long positionUs, SeekParameters seekParameters) {
return mediaPeriod.getAdjustedSeekPositionUs(positionUs - timeOffsetUs, seekParameters)
+ timeOffsetUs;
}

@Override
public long getBufferedPositionUs() {
long bufferedPositionUs = mediaPeriod.getBufferedPositionUs();
return bufferedPositionUs == C.TIME_END_OF_SOURCE
? C.TIME_END_OF_SOURCE
: bufferedPositionUs + timeOffsetUs;
}

@Override
public long getNextLoadPositionUs() {
long nextLoadPositionUs = mediaPeriod.getNextLoadPositionUs();
return nextLoadPositionUs == C.TIME_END_OF_SOURCE
? C.TIME_END_OF_SOURCE
: nextLoadPositionUs + timeOffsetUs;
}

@Override
public boolean continueLoading(long positionUs) {
return mediaPeriod.continueLoading(positionUs - timeOffsetUs);
}

@Override
public boolean isLoading() {
return mediaPeriod.isLoading();
}

@Override
public void reevaluateBuffer(long positionUs) {
mediaPeriod.reevaluateBuffer(positionUs - timeOffsetUs);
}

@Override
public void onPrepared(MediaPeriod mediaPeriod) {
Assertions.checkNotNull(callback).onPrepared(/* mediaPeriod= */ this);
}

@Override
public void onContinueLoadingRequested(MediaPeriod source) {
Assertions.checkNotNull(callback).onContinueLoadingRequested(/* source= */ this);
}
}

private static final class TimeOffsetSampleStream implements SampleStream {

private final SampleStream sampleStream;
private final long timeOffsetUs;

public TimeOffsetSampleStream(SampleStream sampleStream, long timeOffsetUs) {
this.sampleStream = sampleStream;
this.timeOffsetUs = timeOffsetUs;
}

public SampleStream getChildStream() {
return sampleStream;
}

@Override
public boolean isReady() {
return sampleStream.isReady();
}

@Override
public void maybeThrowError() throws IOException {
sampleStream.maybeThrowError();
}

@Override
public int readData(
FormatHolder formatHolder, DecoderInputBuffer buffer, boolean formatRequired) {
int readResult = sampleStream.readData(formatHolder, buffer, formatRequired);
if (readResult == C.RESULT_BUFFER_READ) {
buffer.timeUs = Math.max(0, buffer.timeUs + timeOffsetUs);
}
return readResult;
}

@Override
public int skipData(long positionUs) {
return sampleStream.skipData(positionUs - timeOffsetUs);
}
}
}
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