Allow HlsSampleStreamWrapper to cancel partial media chunk loads

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213439145

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsChunkSource.java

@@ -223,9 +223,6 @@ import java.util.List;
    *     started, the value will be the starting position in the period minus the duration of any
    *     media in previous periods still to be played.
    * @param loadPositionUs The current load position relative to the period start in microseconds.
-   *     If {@code queue} is empty, this is the starting position from which chunks should be
-   *     provided. Else it's equal to {@link HlsMediaChunk#endTimeUs} of the last chunk in the
-   *     {@code queue}.
    * @param queue The queue of buffered {@link HlsMediaChunk}s.
    * @param out A holder to populate.
    */
@@ -237,12 +234,12 @@ import java.util.List;
     long bufferedDurationUs = loadPositionUs - playbackPositionUs;
     long timeToLiveEdgeUs = resolveTimeToLiveEdgeUs(playbackPositionUs);
     if (previous != null && !independentSegments) {
-      // Unless segments are known to be independent, switching variant will require downloading
-      // overlapping segments. Hence we will subtract previous chunk's duration from buffered
+      // Unless segments are known to be independent, switching variant requires downloading
+      // overlapping segments. Hence we subtract the previous segment's duration from the buffered
       // duration.
-      // This may affect the live-streaming adaptive track selection logic, when we are comparing
-      // buffered duration to time to live edge to decide whether to switch. Therefore,
-      // we will subtract this same amount from timeToLiveEdgeUs as well.
+      // This may affect the live-streaming adaptive track selection logic, when we compare the
+      // buffered duration to time-to-live-edge to decide whether to switch. Therefore, we subtract
+      // the duration of the last loaded segment from timeToLiveEdgeUs as well.
       long subtractedDurationUs = previous.getDurationUs();
       bufferedDurationUs = Math.max(0, bufferedDurationUs - subtractedDurationUs);
       if (timeToLiveEdgeUs != C.TIME_UNSET) {
@@ -420,7 +417,7 @@ import java.util.List;
   }
 
   /**
-   * Returns list of {@link MediaChunkIterator}s for upcoming media chunks.
+   * Returns an array of {@link MediaChunkIterator}s for upcoming media chunks.
    *
    * @param previous The previous media chunk. May be null.
    * @param loadPositionUs The position at which the iterators will start.
@@ -458,6 +455,18 @@ import java.util.List;
 
   // Private methods.
 
+  /**
+   * Returns the media sequence number of the segment to load next in {@code mediaPlaylist}.
+   *
+   * @param previous The last (at least partially) loaded segment.
+   * @param switchingVariant Whether the segment to load is not preceded by a segment in the same
+   *     variant.
+   * @param mediaPlaylist The media playlist to which the segment to load belongs.
+   * @param startOfPlaylistInPeriodUs The start of {@code mediaPlaylist} relative to the period
+   *     start in microseconds.
+   * @param loadPositionUs The current load position relative to the period start in microseconds.
+   * @return The media sequence of the segment to load.
+   */
   private long getChunkMediaSequence(
       @Nullable HlsMediaChunk previous,
       boolean switchingVariant,
@@ -480,6 +489,8 @@ import java.util.List;
               /* stayInBounds= */ !playlistTracker.isLive() || previous == null)
           + mediaPlaylist.mediaSequence;
     }
+    // We ignore the case of previous not having loaded completely, in which case we load the next
+    // segment.
     return previous.getNextChunkIndex();
   }
 

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java

@@ -152,7 +152,7 @@ import java.util.concurrent.atomic.AtomicInteger;
     if (previousChunk != null) {
       id3Decoder = previousChunk.id3Decoder;
       id3Data = previousChunk.id3Data;
-      shouldSpliceIn = previousChunk.hlsUrl != hlsUrl;
+      shouldSpliceIn = previousChunk.hlsUrl != hlsUrl || !previousChunk.loadCompleted;
       previousExtractor = previousChunk.discontinuitySequenceNumber != discontinuitySequenceNumber
           || shouldSpliceIn ? null : previousChunk.extractor;
     } else {

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsSampleStreamWrapper.java

@@ -460,9 +460,7 @@ import java.util.List;
           && finishedReadingChunk(mediaChunks.get(discardToMediaChunkIndex))) {
         discardToMediaChunkIndex++;
       }
-      if (discardToMediaChunkIndex > 0) {
-        Util.removeRange(mediaChunks, 0, discardToMediaChunkIndex);
-      }
+      Util.removeRange(mediaChunks, 0, discardToMediaChunkIndex);
       HlsMediaChunk currentChunk = mediaChunks.get(0);
       Format trackFormat = currentChunk.trackFormat;
       if (!trackFormat.equals(downstreamTrackFormat)) {
@@ -554,7 +552,11 @@ import java.util.List;
       loadPositionUs = pendingResetPositionUs;
     } else {
       chunkQueue = readOnlyMediaChunks;
-      loadPositionUs = getLastMediaChunk().endTimeUs;
+      HlsMediaChunk lastMediaChunk = getLastMediaChunk();
+      loadPositionUs =
+          lastMediaChunk.isLoadCompleted()
+              ? lastMediaChunk.endTimeUs
+              : Math.max(lastSeekPositionUs, lastMediaChunk.startTimeUs);
     }
     chunkSource.getNextChunk(positionUs, loadPositionUs, chunkQueue, nextChunkHolder);
     boolean endOfStream = nextChunkHolder.endOfStream;
@@ -666,17 +668,15 @@ import java.util.List;
     boolean blacklistSucceeded = false;
     LoadErrorAction loadErrorAction;
 
-    if (!isMediaChunk || bytesLoaded == 0) {
-      long blacklistDurationMs =
-          loadErrorHandlingPolicy.getBlacklistDurationMsFor(
-              loadable.type, loadDurationMs, error, errorCount);
-      if (blacklistDurationMs != C.TIME_UNSET) {
-        blacklistSucceeded = chunkSource.maybeBlacklistTrack(loadable, blacklistDurationMs);
-      }
+    long blacklistDurationMs =
+        loadErrorHandlingPolicy.getBlacklistDurationMsFor(
+            loadable.type, loadDurationMs, error, errorCount);
+    if (blacklistDurationMs != C.TIME_UNSET) {
+      blacklistSucceeded = chunkSource.maybeBlacklistTrack(loadable, blacklistDurationMs);
     }
 
     if (blacklistSucceeded) {
-      if (isMediaChunk) {
+      if (isMediaChunk && bytesLoaded == 0) {
         HlsMediaChunk removed = mediaChunks.remove(mediaChunks.size() - 1);
         Assertions.checkState(removed == loadable);
         if (mediaChunks.isEmpty()) {
@@ -707,7 +707,7 @@ import java.util.List;
         loadable.endTimeUs,
         elapsedRealtimeMs,
         loadDurationMs,
-        loadable.bytesLoaded(),
+        bytesLoaded,
         error,
         /* wasCanceled= */ !loadErrorAction.isRetry());
 

playbacktests/build.gradle

@@ -33,6 +33,7 @@ android {
 dependencies {
     androidTestImplementation 'androidx.test:rules:' + testRunnerVersion
     androidTestImplementation 'androidx.test:runner:' + testRunnerVersion
+    androidTestImplementation 'com.android.support:support-annotations:' + supportLibraryVersion
     androidTestImplementation project(modulePrefix + 'library-core')
     androidTestImplementation project(modulePrefix + 'library-dash')
     androidTestImplementation project(modulePrefix + 'library-hls')