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Fix available end time calculation for multi-period DASH live streams
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The available end time was accidentally substracted by the start time
of the last period.

To avoid similar time reference confusion in the future, also renaming
many variables and methods to clearly reflect the time reference point.
And to avoid constant conversion, the processManifest method also
attempts to converge to time relative to the start of the window as
quickly as possible.

Issue: #8537
PiperOrigin-RevId: 357001624
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@tonihei @ojw28
tonihei authored and ojw28 committed Feb 12, 2021
1 parent 295e8ba commit 01f57c3
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Showing 3 changed files with 63 additions and 82 deletions.
3 changes: 3 additions & 0 deletions RELEASENOTES.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,9 @@
* Fix a bug where setting playback parameters while using video tunneling
would cause an error to be thrown
([#8570](https://github.com/google/ExoPlayer/issues/8570)).
* DASH:
* Fix playback issue for multi-period DASH live streams
([#8537](https://github.com/google/ExoPlayer/issues/8537)).
* IMA extension:
* Fix handling of repeated ad loads, to avoid ads being discarded if the
user seeks away and then back to a preloaded postroll (for example).
Expand Down
138 changes: 59 additions & 79 deletions library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
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Expand Up @@ -901,77 +901,54 @@ private void processManifest(boolean scheduleRefresh) {
}
}
// Update the window.
boolean windowChangingImplicitly = false;
Period firstPeriod = manifest.getPeriod(0);
int lastPeriodIndex = manifest.getPeriodCount() - 1;
Period lastPeriod = manifest.getPeriod(lastPeriodIndex);
long lastPeriodDurationUs = manifest.getPeriodDurationUs(lastPeriodIndex);
long nowUnixTimeUs = C.msToUs(Util.getNowUnixTimeMs(elapsedRealtimeOffsetMs));
// Get the period-relative start/end times.
long currentStartTimeUs =
getAvailableStartTimeUs(
manifest.getPeriod(0), manifest.getPeriodDurationUs(0), nowUnixTimeUs);
long currentEndTimeUs = getAvailableEndTimeUs(lastPeriod, lastPeriodDurationUs, nowUnixTimeUs);
if (manifest.dynamic && !isIndexExplicit(lastPeriod)) {
// The manifest describes an incomplete live stream. Update the start/end times to reflect the
// live stream duration and the manifest's time shift buffer depth.
long liveStreamEndPositionInLastPeriodUs = currentEndTimeUs - C.msToUs(lastPeriod.startMs);
currentEndTimeUs = min(liveStreamEndPositionInLastPeriodUs, currentEndTimeUs);
if (manifest.timeShiftBufferDepthMs != C.TIME_UNSET) {
long timeShiftBufferDepthUs = C.msToUs(manifest.timeShiftBufferDepthMs);
long offsetInPeriodUs = currentEndTimeUs - timeShiftBufferDepthUs;
int periodIndex = lastPeriodIndex;
while (offsetInPeriodUs < 0 && periodIndex > 0) {
offsetInPeriodUs += manifest.getPeriodDurationUs(--periodIndex);
}
if (periodIndex == 0) {
currentStartTimeUs = max(currentStartTimeUs, offsetInPeriodUs);
} else {
// The time shift buffer starts after the earliest period.
// TODO: Does this ever happen?
currentStartTimeUs = manifest.getPeriodDurationUs(0);
}
}
windowChangingImplicitly = true;
}
long windowDurationUs = currentEndTimeUs - currentStartTimeUs;
for (int i = 0; i < manifest.getPeriodCount() - 1; i++) {
windowDurationUs += manifest.getPeriodDurationUs(i);
}

long windowStartTimeMs = C.TIME_UNSET;
if (manifest.availabilityStartTimeMs != C.TIME_UNSET) {
windowStartTimeMs =
manifest.availabilityStartTimeMs
+ manifest.getPeriod(0).startMs
+ C.usToMs(currentStartTimeUs);
}

long windowDefaultStartPositionUs = 0;
long windowStartTimeInManifestUs =
getAvailableStartTimeInManifestUs(
firstPeriod, manifest.getPeriodDurationUs(0), nowUnixTimeUs);
long windowEndTimeInManifestUs =
getAvailableEndTimeInManifestUs(lastPeriod, lastPeriodDurationUs, nowUnixTimeUs);
boolean windowChangingImplicitly = manifest.dynamic && !isIndexExplicit(lastPeriod);
if (windowChangingImplicitly && manifest.timeShiftBufferDepthMs != C.TIME_UNSET) {
// Update the available start time to reflect the manifest's time shift buffer depth.
long timeShiftBufferStartTimeInManifestUs =
windowEndTimeInManifestUs - C.msToUs(manifest.timeShiftBufferDepthMs);
windowStartTimeInManifestUs =
max(windowStartTimeInManifestUs, timeShiftBufferStartTimeInManifestUs);
}
long windowDurationUs = windowEndTimeInManifestUs - windowStartTimeInManifestUs;
long windowStartUnixTimeMs = C.TIME_UNSET;
long windowDefaultPositionUs = 0;
if (manifest.dynamic) {
updateMediaItemLiveConfiguration(
/* nowPeriodTimeUs= */ currentStartTimeUs + nowUnixTimeUs - C.msToUs(windowStartTimeMs),
/* windowStartPeriodTimeUs= */ currentStartTimeUs,
/* windowEndPeriodTimeUs= */ currentEndTimeUs);
windowDefaultStartPositionUs =
nowUnixTimeUs - C.msToUs(windowStartTimeMs + liveConfiguration.targetOffsetMs);
long minimumDefaultStartPositionUs =
checkState(manifest.availabilityStartTimeMs != C.TIME_UNSET);
long nowInWindowUs =
nowUnixTimeUs - C.msToUs(manifest.availabilityStartTimeMs) - windowStartTimeInManifestUs;
updateMediaItemLiveConfiguration(nowInWindowUs, windowDurationUs);
windowStartUnixTimeMs =
manifest.availabilityStartTimeMs + C.usToMs(windowStartTimeInManifestUs);
windowDefaultPositionUs = nowInWindowUs - C.msToUs(liveConfiguration.targetOffsetMs);
long minimumWindowDefaultPositionUs =
min(MIN_LIVE_DEFAULT_START_POSITION_US, windowDurationUs / 2);
if (windowDefaultStartPositionUs < minimumDefaultStartPositionUs) {
// The default start position is too close to the start of the live window. Set it to the
// minimum default start position provided the window is at least twice as big. Else set
// it to the middle of the window.
windowDefaultStartPositionUs = minimumDefaultStartPositionUs;
if (windowDefaultPositionUs < minimumWindowDefaultPositionUs) {
// The default position is too close to the start of the live window. Set it to the minimum
// default position provided the window is at least twice as big. Else set it to the middle
// of the window.
windowDefaultPositionUs = minimumWindowDefaultPositionUs;
}
}
long offsetInFirstPeriodUs = windowStartTimeInManifestUs - C.msToUs(firstPeriod.startMs);
DashTimeline timeline =
new DashTimeline(
manifest.availabilityStartTimeMs,
windowStartTimeMs,
windowStartUnixTimeMs,
elapsedRealtimeOffsetMs,
firstPeriodId,
/* offsetInFirstPeriodUs= */ currentStartTimeUs,
offsetInFirstPeriodUs,
windowDurationUs,
windowDefaultStartPositionUs,
windowDefaultPositionUs,
manifest,
mediaItem,
manifest.dynamic ? liveConfiguration : null);
Expand Down Expand Up @@ -1008,16 +985,15 @@ private void processManifest(boolean scheduleRefresh) {
}
}

private void updateMediaItemLiveConfiguration(
long nowPeriodTimeUs, long windowStartPeriodTimeUs, long windowEndPeriodTimeUs) {
private void updateMediaItemLiveConfiguration(long nowInWindowUs, long windowDurationUs) {
long maxLiveOffsetMs;
if (mediaItem.liveConfiguration.maxOffsetMs != C.TIME_UNSET) {
maxLiveOffsetMs = mediaItem.liveConfiguration.maxOffsetMs;
} else if (manifest.serviceDescription != null
&& manifest.serviceDescription.maxOffsetMs != C.TIME_UNSET) {
maxLiveOffsetMs = manifest.serviceDescription.maxOffsetMs;
} else {
maxLiveOffsetMs = C.usToMs(nowPeriodTimeUs - windowStartPeriodTimeUs);
maxLiveOffsetMs = C.usToMs(nowInWindowUs);
}
long minLiveOffsetMs;
if (mediaItem.liveConfiguration.minOffsetMs != C.TIME_UNSET) {
Expand All @@ -1026,7 +1002,7 @@ private void updateMediaItemLiveConfiguration(
&& manifest.serviceDescription.minOffsetMs != C.TIME_UNSET) {
minLiveOffsetMs = manifest.serviceDescription.minOffsetMs;
} else {
minLiveOffsetMs = C.usToMs(nowPeriodTimeUs - windowEndPeriodTimeUs);
minLiveOffsetMs = C.usToMs(nowInWindowUs - windowDurationUs);
if (minLiveOffsetMs < 0 && maxLiveOffsetMs > 0) {
// The current time is in the window, so assume all clocks are synchronized and set the
// minimum to a live offset of zero.
Expand All @@ -1052,12 +1028,10 @@ private void updateMediaItemLiveConfiguration(
targetOffsetMs = minLiveOffsetMs;
}
if (targetOffsetMs > maxLiveOffsetMs) {
long windowDurationUs = windowEndPeriodTimeUs - windowStartPeriodTimeUs;
long liveOffsetAtWindowStartUs = nowPeriodTimeUs - windowStartPeriodTimeUs;
long safeDistanceFromWindowStartUs =
min(MIN_LIVE_DEFAULT_START_POSITION_US, windowDurationUs / 2);
long maxTargetOffsetForSafeDistanceToWindowStartMs =
C.usToMs(liveOffsetAtWindowStartUs - safeDistanceFromWindowStartUs);
C.usToMs(nowInWindowUs - safeDistanceFromWindowStartUs);
targetOffsetMs =
Util.constrainValue(
maxTargetOffsetForSafeDistanceToWindowStartMs, minLiveOffsetMs, maxLiveOffsetMs);
Expand Down Expand Up @@ -1147,9 +1121,10 @@ private static long getIntervalUntilNextManifestRefreshMs(
return LongMath.divide(intervalUs, 1000, RoundingMode.CEILING);
}

private static long getAvailableStartTimeUs(
private static long getAvailableStartTimeInManifestUs(
Period period, long periodDurationUs, long nowUnixTimeUs) {
long availableStartTimeUs = 0;
long periodStartTimeInManifestUs = C.msToUs(period.startMs);
long availableStartTimeInManifestUs = periodStartTimeInManifestUs;
boolean haveAudioVideoAdaptationSets = hasVideoOrAudioAdaptationSets(period);
for (int i = 0; i < period.adaptationSets.size(); i++) {
AdaptationSet adaptationSet = period.adaptationSets.get(i);
Expand All @@ -1162,23 +1137,26 @@ private static long getAvailableStartTimeUs(
}
@Nullable DashSegmentIndex index = representations.get(0).getIndex();
if (index == null) {
return 0;
return periodStartTimeInManifestUs;
}
int availableSegmentCount = index.getAvailableSegmentCount(periodDurationUs, nowUnixTimeUs);
if (availableSegmentCount == 0) {
return 0;
return periodStartTimeInManifestUs;
}
long firstAvailableSegmentNum =
index.getFirstAvailableSegmentNum(periodDurationUs, nowUnixTimeUs);
long adaptationSetAvailableStartTimeUs = index.getTimeUs(firstAvailableSegmentNum);
availableStartTimeUs = max(availableStartTimeUs, adaptationSetAvailableStartTimeUs);
long adaptationSetAvailableStartTimeInManifestUs =
periodStartTimeInManifestUs + index.getTimeUs(firstAvailableSegmentNum);
availableStartTimeInManifestUs =
max(availableStartTimeInManifestUs, adaptationSetAvailableStartTimeInManifestUs);
}
return availableStartTimeUs;
return availableStartTimeInManifestUs;
}

private static long getAvailableEndTimeUs(
private static long getAvailableEndTimeInManifestUs(
Period period, long periodDurationUs, long nowUnixTimeUs) {
long availableEndTimeUs = Long.MAX_VALUE;
long periodStartTimeInManifestUs = C.msToUs(period.startMs);
long availableEndTimeInManifestUs = Long.MAX_VALUE;
boolean haveAudioVideoAdaptationSets = hasVideoOrAudioAdaptationSets(period);
for (int i = 0; i < period.adaptationSets.size(); i++) {
AdaptationSet adaptationSet = period.adaptationSets.get(i);
Expand All @@ -1191,21 +1169,23 @@ private static long getAvailableEndTimeUs(
}
@Nullable DashSegmentIndex index = representations.get(0).getIndex();
if (index == null) {
return periodDurationUs;
return periodStartTimeInManifestUs + periodDurationUs;
}
int availableSegmentCount = index.getAvailableSegmentCount(periodDurationUs, nowUnixTimeUs);
if (availableSegmentCount == 0) {
return 0;
return periodStartTimeInManifestUs;
}
long firstAvailableSegmentNum =
index.getFirstAvailableSegmentNum(periodDurationUs, nowUnixTimeUs);
long lastAvailableSegmentNum = firstAvailableSegmentNum + availableSegmentCount - 1;
long adaptationSetAvailableEndTimeUs =
index.getTimeUs(lastAvailableSegmentNum)
long adaptationSetAvailableEndTimeInManifestUs =
periodStartTimeInManifestUs
+ index.getTimeUs(lastAvailableSegmentNum)
+ index.getDurationUs(lastAvailableSegmentNum, periodDurationUs);
availableEndTimeUs = min(availableEndTimeUs, adaptationSetAvailableEndTimeUs);
availableEndTimeInManifestUs =
min(availableEndTimeInManifestUs, adaptationSetAvailableEndTimeInManifestUs);
}
return availableEndTimeUs;
return availableEndTimeInManifestUs;
}

private static boolean isIndexExplicit(Period period) {
Expand Down
4 changes: 1 addition & 3 deletions library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/Period.java
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,7 @@ public class Period {
*/
@Nullable public final String id;

/**
* The start time of the period in milliseconds.
*/
/** The start time of the period in milliseconds, relative to the start of the manifest. */
public final long startMs;

/**
Expand Down

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