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Misc cleanup / clarification for bandwidth improvements

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PiperOrigin-RevId: 369315524
This commit is contained in:
olly 2021-04-19 23:26:49 +01:00 committed by Oliver Woodman
parent 7a13163664
commit f2c13d9f44
2 changed files with 23 additions and 10 deletions
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31
library/core/src/main/java/com/google/android/exoplayer2/trackselection/AdaptiveTrackSelection.java
View File

@ -15,6 +15,8 @@
*/
package com.google.android.exoplayer2.trackselection;
import static java.lang.Math.max;
import androidx.annotation.CallSuper;
import androidx.annotation.Nullable;
import com.google.android.exoplayer2.C;
@ -329,7 +331,7 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
List<? extends MediaChunk> queue,
MediaChunkIterator[] mediaChunkIterators) {
long nowMs = clock.elapsedRealtime();
long chunkDurationUs = getChunkDurationUs(mediaChunkIterators, queue);
long chunkDurationUs = getNextChunkDurationUs(mediaChunkIterators, queue);
// Make initial selection
if (reason == C.SELECTION_REASON_UNKNOWN) {
@ -406,7 +408,7 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
if (playoutBufferedDurationBeforeLastChunkUs < minDurationToRetainAfterDiscardUs) {
return queueSize;
}
int idealSelectedIndex = determineIdealSelectedIndex(nowMs, getChunkDurationUs(queue));
int idealSelectedIndex = determineIdealSelectedIndex(nowMs, getLastChunkDurationUs(queue));
Format idealFormat = getFormat(idealSelectedIndex);
// If the chunks contain video, discard from the first SD chunk beyond
// minDurationToRetainAfterDiscardUs whose resolution and bitrate are both lower than the ideal
@ -498,24 +500,34 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
: minDurationForQualityIncreaseUs;
}
private long getChunkDurationUs(
/**
* Returns a best estimate of the duration of the next chunk, in microseconds, or {@link
* C#TIME_UNSET} if an estimate could not be determined.
*/
private long getNextChunkDurationUs(
MediaChunkIterator[] mediaChunkIterators, List<? extends MediaChunk> queue) {
// First, try to get the chunk duration for currently selected format.
// Try to get the next chunk duration for the currently selected format.
if (selectedIndex < mediaChunkIterators.length && mediaChunkIterators[selectedIndex].next()) {
MediaChunkIterator iterator = mediaChunkIterators[selectedIndex];
return iterator.getChunkEndTimeUs() - iterator.getChunkStartTimeUs();
}
// Second, try to get the chunk duration for another format.
// Try to get the next chunk duration for another format, on the assumption that chunks
// belonging to different formats are likely to have identical or similar durations.
for (MediaChunkIterator iterator : mediaChunkIterators) {
if (iterator.next()) {
return iterator.getChunkEndTimeUs() - iterator.getChunkStartTimeUs();
}
}
// Third, try to get chunk duration for previous chunk in the queue.
return getChunkDurationUs(queue);
// Try to get chunk duration for last chunk in the queue, on the assumption that the next chunk
// is likely to have a similar duration.
return getLastChunkDurationUs(queue);
}
private long getChunkDurationUs(List<? extends MediaChunk> queue) {
/**
* Returns the duration of the last chunk in the queue, in microseconds, or {@link C#TIME_UNSET}
* if the queue is empty or if the last chunk has an undefined start or end time.
*/
private long getLastChunkDurationUs(List<? extends MediaChunk> queue) {
if (queue.isEmpty()) {
return C.TIME_UNSET;
}
@ -552,7 +564,8 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
if (timeToFirstByteEstimateUs == C.TIME_UNSET || chunkDurationUs == C.TIME_UNSET) {
return (long) (cautiousBandwidthEstimate / playbackSpeed);
}
float availableTimeToLoadUs = chunkDurationUs / playbackSpeed - timeToFirstByteEstimateUs;
float availableTimeToLoadUs =
max(chunkDurationUs / playbackSpeed - timeToFirstByteEstimateUs, 0);
return (long) (cautiousBandwidthEstimate * availableTimeToLoadUs / chunkDurationUs);
}

2
library/core/src/main/java/com/google/android/exoplayer2/upstream/TimeToFirstByteEstimator.java
View File

@ -25,7 +25,7 @@ public interface TimeToFirstByteEstimator {
*/
long getTimeToFirstByteEstimateUs();
/** Resets the estimator. The estimator should drop all samples and reset to its initial state. */
/** Resets the estimator. */
void reset();
/**