Support delta updates for media playlists

Issue: #5011
PiperOrigin-RevId: 339093145

library/hls/build.gradle

@@ -29,6 +29,7 @@ dependencies {
     compileOnly 'org.checkerframework:checker-compat-qual:' + checkerframeworkCompatVersion
     compileOnly 'org.jetbrains.kotlin:kotlin-annotations-jvm:' + kotlinAnnotationsVersion
     implementation project(modulePrefix + 'library-core')
+    testImplementation project(modulePrefix + 'robolectricutils')
     testImplementation project(modulePrefix + 'testutils')
     testImplementation project(modulePrefix + 'testdata')
     testImplementation 'org.robolectric:robolectric:' + robolectricVersion

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

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.source.hls.playlist;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
 import static java.lang.Math.max;
 
 import android.net.Uri;
@@ -163,7 +164,7 @@ public final class DefaultHlsPlaylistTracker
 
   @Override
   public void addListener(PlaylistEventListener listener) {
-    Assertions.checkNotNull(listener);
+    checkNotNull(listener);
     listeners.add(listener);
   }
 
@@ -390,7 +391,7 @@ public final class DefaultHlsPlaylistTracker
   }
 
   private HlsMediaPlaylist getLatestPlaylistSnapshot(
-      HlsMediaPlaylist oldPlaylist, HlsMediaPlaylist loadedPlaylist) {
+      @Nullable HlsMediaPlaylist oldPlaylist, HlsMediaPlaylist loadedPlaylist) {
     if (!loadedPlaylist.isNewerThan(oldPlaylist)) {
       if (loadedPlaylist.hasEndTag) {
         // If the loaded playlist has an end tag but is not newer than the old playlist then we have
@@ -408,7 +409,7 @@ public final class DefaultHlsPlaylistTracker
   }
 
   private long getLoadedPlaylistStartTimeUs(
-      HlsMediaPlaylist oldPlaylist, HlsMediaPlaylist loadedPlaylist) {
+      @Nullable HlsMediaPlaylist oldPlaylist, HlsMediaPlaylist loadedPlaylist) {
     if (loadedPlaylist.hasProgramDateTime) {
       return loadedPlaylist.startTimeUs;
     }
@@ -430,7 +431,7 @@ public final class DefaultHlsPlaylistTracker
   }
 
   private int getLoadedPlaylistDiscontinuitySequence(
-      HlsMediaPlaylist oldPlaylist, HlsMediaPlaylist loadedPlaylist) {
+      @Nullable HlsMediaPlaylist oldPlaylist, HlsMediaPlaylist loadedPlaylist) {
     if (loadedPlaylist.hasDiscontinuitySequence) {
       return loadedPlaylist.discontinuitySequence;
     }
@@ -464,7 +465,7 @@ public final class DefaultHlsPlaylistTracker
 
     private final Uri playlistUrl;
     private final Loader mediaPlaylistLoader;
-    private final ParsingLoadable<HlsPlaylist> mediaPlaylistLoadable;
+    private final DataSource mediaPlaylistDataSource;
 
     @Nullable private HlsMediaPlaylist playlistSnapshot;
     private long lastSnapshotLoadMs;
@@ -477,12 +478,7 @@ public final class DefaultHlsPlaylistTracker
     public MediaPlaylistBundle(Uri playlistUrl) {
       this.playlistUrl = playlistUrl;
       mediaPlaylistLoader = new Loader("DefaultHlsPlaylistTracker:MediaPlaylist");
-      mediaPlaylistLoadable =
+      mediaPlaylistDataSource = dataSourceFactory.createDataSource(C.DATA_TYPE_MANIFEST);
-          new ParsingLoadable<>(
-              dataSourceFactory.createDataSource(C.DATA_TYPE_MANIFEST),
-              playlistUrl,
-              C.DATA_TYPE_MANIFEST,
-              mediaPlaylistParser);
     }
 
     @Nullable
@@ -533,7 +529,7 @@ public final class DefaultHlsPlaylistTracker
     @Override
     public void onLoadCompleted(
         ParsingLoadable<HlsPlaylist> loadable, long elapsedRealtimeMs, long loadDurationMs) {
-      HlsPlaylist result = loadable.getResult();
+      @Nullable HlsPlaylist result = loadable.getResult();
       LoadEventInfo loadEventInfo =
           new LoadEventInfo(
               loadable.loadTaskId,
@@ -631,6 +627,12 @@ public final class DefaultHlsPlaylistTracker
     // Internal methods.
 
     private void loadPlaylistImmediately() {
+      ParsingLoadable<HlsPlaylist> mediaPlaylistLoadable =
+          new ParsingLoadable<>(
+              mediaPlaylistDataSource,
+              getMediaPlaylistUriForRequest(playlistUrl, playlistSnapshot),
+              C.DATA_TYPE_MANIFEST,
+              mediaPlaylistParser);
       long elapsedRealtime =
           mediaPlaylistLoader.startLoading(
               mediaPlaylistLoadable,
@@ -644,7 +646,11 @@ public final class DefaultHlsPlaylistTracker
 
     private void processLoadedPlaylist(
         HlsMediaPlaylist loadedPlaylist, LoadEventInfo loadEventInfo) {
-      HlsMediaPlaylist oldPlaylist = playlistSnapshot;
+      @Nullable HlsMediaPlaylist oldPlaylist = playlistSnapshot;
+      loadedPlaylist =
+          loadedPlaylist.skippedSegmentCount > 0
+              ? loadedPlaylist.expandSkippedSegments(checkNotNull(playlistSnapshot))
+              : loadedPlaylist;
       long currentTimeMs = SystemClock.elapsedRealtime();
       lastSnapshotLoadMs = currentTimeMs;
       playlistSnapshot = getLatestPlaylistSnapshot(oldPlaylist, loadedPlaylist);
@@ -695,6 +701,18 @@ public final class DefaultHlsPlaylistTracker
       }
     }
 
+    private Uri getMediaPlaylistUriForRequest(
+        Uri playlistUri, @Nullable HlsMediaPlaylist currentMediaPlaylist) {
+      if (currentMediaPlaylist == null
+          || currentMediaPlaylist.serverControl.skipUntilUs == C.TIME_UNSET) {
+        return playlistUri;
+      }
+      Uri.Builder uriBuilder = playlistUri.buildUpon();
+      uriBuilder.appendQueryParameter(
+          "_HLS_skip", currentMediaPlaylist.serverControl.canSkipDateRanges ? "v2" : "YES");
+      return uriBuilder.build();
+    }
+
     /**
      * Excludes the playlist.
      *

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

@@ -15,6 +15,8 @@
  */
 package com.google.android.exoplayer2.source.hls.playlist;
 
+import static com.google.android.exoplayer2.util.Assertions.checkArgument;
+
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
@@ -23,6 +25,7 @@ import com.google.android.exoplayer2.offline.StreamKey;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
@@ -275,9 +278,9 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
    * The list of segments in the playlist.
    */
   public final List<Segment> segments;
-  /**
+  /** The number of skipped segments. */
-   * The total duration of the playlist in microseconds.
+  public int skippedSegmentCount;
-   */
+  /** The total duration of the playlist in microseconds. */
   public final long durationUs;
   /** The attributes of the #EXT-X-SERVER-CONTROL header. */
   public final ServerControl serverControl;
@@ -317,6 +320,7 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
       boolean hasProgramDateTime,
       @Nullable DrmInitData protectionSchemes,
       List<Segment> segments,
+      int skippedSegmentCount,
       ServerControl serverControl) {
     super(baseUri, tags, hasIndependentSegments);
     this.playlistType = playlistType;
@@ -331,6 +335,7 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
     this.hasProgramDateTime = hasProgramDateTime;
     this.protectionSchemes = protectionSchemes;
     this.segments = Collections.unmodifiableList(segments);
+    this.skippedSegmentCount = skippedSegmentCount;
     if (!segments.isEmpty()) {
       Segment last = segments.get(segments.size() - 1);
       durationUs = last.relativeStartTimeUs + last.durationUs;
@@ -353,7 +358,7 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
    * @param other The playlist to compare.
    * @return Whether this playlist is newer than {@code other}.
    */
-  public boolean isNewerThan(HlsMediaPlaylist other) {
+  public boolean isNewerThan(@Nullable HlsMediaPlaylist other) {
     if (other == null || mediaSequence > other.mediaSequence) {
       return true;
     }
@@ -361,8 +366,8 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
       return false;
     }
     // The media sequences are equal.
-    int segmentCount = segments.size();
+    int segmentCount = segments.size() + skippedSegmentCount;
-    int otherSegmentCount = other.segments.size();
+    int otherSegmentCount = other.segments.size() + other.skippedSegmentCount;
     return segmentCount > otherSegmentCount
         || (segmentCount == otherSegmentCount && hasEndTag && !other.hasEndTag);
   }
@@ -374,6 +379,50 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
     return startTimeUs + durationUs;
   }
 
+  /**
+   * Merges the skipped segments of the previous playlist and returns a copy with a {@link
+   * #skippedSegmentCount} of 0.
+   *
+   * @param previousPlaylist The previous playlist with a {@link #skippedSegmentCount} of zero.
+   * @return A new playlist with a complete list of segments.
+   */
+  public HlsMediaPlaylist expandSkippedSegments(HlsMediaPlaylist previousPlaylist) {
+    if (skippedSegmentCount == 0) {
+      return this;
+    }
+    checkArgument(previousPlaylist.skippedSegmentCount == 0);
+    List<Segment> mergedSegments = new ArrayList<>();
+    long mediaSequence = this.mediaSequence;
+    int startIndex = (int) (mediaSequence - previousPlaylist.mediaSequence);
+    int endIndex = startIndex + skippedSegmentCount;
+    if (startIndex >= 0 && endIndex <= previousPlaylist.segments.size()) {
+      mergedSegments.addAll(previousPlaylist.segments.subList(startIndex, endIndex));
+    } else {
+      // Adjust the media sequence if the old playlist doesn't contain all of the skipped segments.
+      mediaSequence += skippedSegmentCount;
+    }
+    mergedSegments.addAll(segments);
+    return new HlsMediaPlaylist(
+        playlistType,
+        baseUri,
+        tags,
+        startOffsetUs,
+        startTimeUs,
+        hasDiscontinuitySequence,
+        discontinuitySequence,
+        mediaSequence,
+        version,
+        targetDurationUs,
+        partTargetDurationUs,
+        hasIndependentSegments,
+        hasEndTag,
+        hasProgramDateTime,
+        protectionSchemes,
+        mergedSegments,
+        /* skippedSegmentCount= */ 0,
+        serverControl);
+  }
+
   /**
    * Returns a playlist identical to this one except for the start time, the discontinuity sequence
    * and {@code hasDiscontinuitySequence} values. The first two are set to the specified values,
@@ -401,6 +450,7 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
         hasProgramDateTime,
         protectionSchemes,
         segments,
+        skippedSegmentCount,
         serverControl);
   }
 
@@ -429,6 +479,7 @@ public final class HlsMediaPlaylist extends HlsPlaylist {
         hasProgramDateTime,
         protectionSchemes,
         segments,
+        skippedSegmentCount,
         serverControl);
   }
 

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

@@ -90,6 +90,7 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
   private static final String TAG_SESSION_KEY = "#EXT-X-SESSION-KEY";
   private static final String TAG_BYTERANGE = "#EXT-X-BYTERANGE";
   private static final String TAG_GAP = "#EXT-X-GAP";
+  private static final String TAG_SKIP = "#EXT-X-SKIP";
 
   private static final String TYPE_AUDIO = "AUDIO";
   private static final String TYPE_VIDEO = "VIDEO";
@@ -135,6 +136,8 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
       Pattern.compile("CAN-SKIP-UNTIL=([\\d\\.]+)\\b");
   private static final Pattern REGEX_CAN_SKIP_DATE_RANGES =
       compileBooleanAttrPattern("CAN-SKIP-DATERANGES");
+  private static final Pattern REGEX_SKIPPED_SEGMENTS =
+      Pattern.compile("SKIPPED-SEGMENTS=(\\d+)\\b");
   private static final Pattern REGEX_HOLD_BACK = Pattern.compile("[:|,]HOLD-BACK=([\\d\\.]+)\\b");
   private static final Pattern REGEX_PART_HOLD_BACK =
       Pattern.compile("PART-HOLD-BACK=([\\d\\.]+)\\b");
@@ -609,6 +612,7 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
             /* holdBackUs= */ C.TIME_UNSET,
             /* partHoldBackUs= */ C.TIME_UNSET,
             /* canBlockReload= */ false);
+    int skippedSegmentCount = 0;
 
     DrmInitData playlistProtectionSchemes = null;
     String fullSegmentEncryptionKeyUri = null;
@@ -692,6 +696,8 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
         segmentDurationUs =
             (long) (parseDoubleAttr(line, REGEX_MEDIA_DURATION) * C.MICROS_PER_SECOND);
         segmentTitle = parseOptionalStringAttr(line, REGEX_MEDIA_TITLE, "", variableDefinitions);
+      } else if (line.startsWith(TAG_SKIP)) {
+        skippedSegmentCount = parseIntAttr(line, REGEX_SKIPPED_SEGMENTS);
       } else if (line.startsWith(TAG_KEY)) {
         String method = parseStringAttr(line, REGEX_METHOD, variableDefinitions);
         String keyFormat =
@@ -832,6 +838,7 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
         /* hasProgramDateTime= */ playlistStartTimeUs != 0,
         playlistProtectionSchemes,
         segments,
+        skippedSegmentCount,
         serverControl);
   }
 

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTrackerTest.java

@@ -0,0 +1,296 @@
+/*
+ * Copyright 2020 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 com.google.android.exoplayer2.source.hls.playlist;
+
+import static com.google.android.exoplayer2.util.Assertions.checkArgument;
+import static com.google.android.exoplayer2.util.Assertions.checkState;
+import static com.google.common.truth.Truth.assertThat;
+
+import android.net.Uri;
+import androidx.annotation.Nullable;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.robolectric.RobolectricUtil;
+import com.google.android.exoplayer2.source.MediaSourceEventListener;
+import com.google.android.exoplayer2.testutil.FakeDataSet;
+import com.google.android.exoplayer2.testutil.FakeDataSource;
+import com.google.android.exoplayer2.testutil.TestUtil;
+import com.google.android.exoplayer2.upstream.ByteArrayDataSource;
+import com.google.android.exoplayer2.upstream.DataSource;
+import com.google.android.exoplayer2.upstream.DataSpec;
+import com.google.android.exoplayer2.upstream.DefaultLoadErrorHandlingPolicy;
+import com.google.android.exoplayer2.upstream.TransferListener;
+import java.io.IOException;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unit test for {@link DefaultHlsPlaylistTracker}. */
+@RunWith(AndroidJUnit4.class)
+public class DefaultHlsPlaylistTrackerTest {
+
+  private static final String SAMPLE_M3U8_LIVE_MASTER = "media/m3u8/live_low_latency_master";
+  private static final String SAMPLE_M3U8_LIVE_MASTER_MEDIA_URI_WITH_PARAM =
+      "media/m3u8/live_low_latency_master_media_uri_with_param";
+  private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL =
+      "media/m3u8/live_low_latency_media_can_skip_until";
+  private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_DATERANGES =
+      "media/m3u8/live_low_latency_media_can_skip_dateranges";
+  private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED =
+      "media/m3u8/live_low_latency_media_can_skip_skipped";
+  private static final String
+      SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED_MEDIA_SEQUENCE_NO_OVERLAPPING =
+          "media/m3u8/live_low_latency_media_can_skip_skipped_media_sequence_no_overlapping";
+  private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_NOT_SKIP =
+      "media/m3u8/live_low_latency_media_can_not_skip";
+  private static final String SAMPLE_M3U8_LIVE_MEDIA_CAN_NOT_SKIP_NEXT =
+      "media/m3u8/live_low_latency_media_can_not_skip_next";
+
+  @Test
+  public void start_playlistCanNotSkip_requestsFullUpdate() throws IOException, TimeoutException {
+
+    Uri masterPlaylistUri = Uri.parse("fake://foo.bar/master.m3u8");
+    Queue<DataSource> dataSourceQueue = new ArrayDeque<>();
+    dataSourceQueue.add(new ByteArrayDataSource(getBytes(SAMPLE_M3U8_LIVE_MASTER)));
+    dataSourceQueue.add(
+        new DataSourceList(
+            new ByteArrayDataSource(getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_NOT_SKIP)),
+            new ByteArrayDataSource(getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_NOT_SKIP_NEXT))));
+
+    List<HlsMediaPlaylist> mediaPlaylists =
+        runPlaylistTrackerAndCollectMediaPlaylists(
+            /* dataSourceFactory= */ dataSourceQueue::remove,
+            masterPlaylistUri,
+            /* awaitedMediaPlaylistCount= */ 2);
+
+    HlsMediaPlaylist firstFullPlaylist = mediaPlaylists.get(0);
+    assertThat(firstFullPlaylist.mediaSequence).isEqualTo(10);
+    assertThat(firstFullPlaylist.segments.get(0).url).isEqualTo("fileSequence10.ts");
+    assertThat(firstFullPlaylist.segments.get(5).url).isEqualTo("fileSequence15.ts");
+    assertThat(firstFullPlaylist.segments).hasSize(6);
+    HlsMediaPlaylist secondFullPlaylist = mediaPlaylists.get(1);
+    assertThat(secondFullPlaylist.mediaSequence).isEqualTo(11);
+    assertThat(secondFullPlaylist.skippedSegmentCount).isEqualTo(0);
+    assertThat(secondFullPlaylist.segments.get(0).url).isEqualTo("fileSequence11.ts");
+    assertThat(secondFullPlaylist.segments.get(5).url).isEqualTo("fileSequence16.ts");
+    assertThat(secondFullPlaylist.segments).hasSize(6);
+    assertThat(secondFullPlaylist.segments).containsNoneIn(firstFullPlaylist.segments);
+  }
+
+  @Test
+  public void start_playlistCanSkip_requestsDeltaUpdateAndExpandsSkippedSegments()
+      throws IOException, TimeoutException {
+    Uri masterPlaylistUri = Uri.parse("fake://foo.bar/master.m3u8");
+    Uri mediaPlaylistUri = Uri.parse("fake://foo.bar/media0/playlist.m3u8");
+    Uri mediaPlaylistSkippedUri = Uri.parse(mediaPlaylistUri + "?_HLS_skip=YES");
+    FakeDataSet fakeDataSet =
+        new FakeDataSet()
+            .setData(masterPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MASTER))
+            .setData(mediaPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL))
+            .setData(mediaPlaylistSkippedUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED));
+
+    List<HlsMediaPlaylist> mediaPlaylists =
+        runPlaylistTrackerAndCollectMediaPlaylists(
+            new FakeDataSource.Factory().setFakeDataSet(fakeDataSet),
+            masterPlaylistUri,
+            /* awaitedMediaPlaylistCount= */ 2);
+
+    HlsMediaPlaylist initialPlaylistWithAllSegments = mediaPlaylists.get(0);
+    assertThat(initialPlaylistWithAllSegments.mediaSequence).isEqualTo(10);
+    assertThat(initialPlaylistWithAllSegments.segments).hasSize(6);
+    HlsMediaPlaylist mergedPlaylist = mediaPlaylists.get(1);
+    assertThat(mergedPlaylist.mediaSequence).isEqualTo(11);
+    assertThat(mergedPlaylist.skippedSegmentCount).isEqualTo(0);
+    assertThat(mergedPlaylist.segments).hasSize(6);
+    // First 2 segments of the merged playlist need to be copied from the previous playlist.
+    assertThat(mergedPlaylist.segments.subList(0, 2))
+        .containsExactlyElementsIn(initialPlaylistWithAllSegments.segments.subList(1, 3))
+        .inOrder();
+    assertThat(mergedPlaylist.segments.get(2).url)
+        .isEqualTo(initialPlaylistWithAllSegments.segments.get(3).url);
+  }
+
+  @Test
+  public void start_playlistCanSkip_missingSegments_correctedMediaSequence()
+      throws IOException, TimeoutException {
+    Uri masterPlaylistUri = Uri.parse("fake://foo.bar/master.m3u8");
+    Uri mediaPlaylistUri = Uri.parse("fake://foo.bar/media0/playlist.m3u8");
+    Uri mediaPlaylistSkippedUri = Uri.parse(mediaPlaylistUri + "?_HLS_skip=YES");
+    FakeDataSet fakeDataSet =
+        new FakeDataSet()
+            .setData(masterPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MASTER))
+            .setData(mediaPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL))
+            .setData(
+                mediaPlaylistSkippedUri,
+                getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED_MEDIA_SEQUENCE_NO_OVERLAPPING));
+
+    List<HlsMediaPlaylist> mediaPlaylists =
+        runPlaylistTrackerAndCollectMediaPlaylists(
+            new FakeDataSource.Factory().setFakeDataSet(fakeDataSet),
+            masterPlaylistUri,
+            /* awaitedMediaPlaylistCount= */ 2);
+
+    HlsMediaPlaylist initialPlaylistWithAllSegments = mediaPlaylists.get(0);
+    assertThat(initialPlaylistWithAllSegments.mediaSequence).isEqualTo(10);
+    assertThat(initialPlaylistWithAllSegments.segments).hasSize(6);
+    HlsMediaPlaylist mergedPlaylist = mediaPlaylists.get(1);
+    assertThat(mergedPlaylist.mediaSequence).isEqualTo(22);
+    assertThat(mergedPlaylist.skippedSegmentCount).isEqualTo(0);
+    assertThat(mergedPlaylist.segments).hasSize(4);
+  }
+
+  @Test
+  public void start_playlistCanSkipDataRanges_requestsDeltaUpdateV2()
+      throws IOException, TimeoutException {
+    Uri masterPlaylistUri = Uri.parse("fake://foo.bar/master.m3u8");
+    Uri mediaPlaylistUri = Uri.parse("fake://foo.bar/media0/playlist.m3u8");
+    // Expect _HLS_skip parameter with value v2.
+    Uri mediaPlaylistSkippedUri = Uri.parse(mediaPlaylistUri + "?_HLS_skip=v2");
+    FakeDataSet fakeDataSet =
+        new FakeDataSet()
+            .setData(masterPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MASTER))
+            .setData(mediaPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_DATERANGES))
+            .setData(mediaPlaylistSkippedUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED));
+
+    List<HlsMediaPlaylist> mediaPlaylists =
+        runPlaylistTrackerAndCollectMediaPlaylists(
+            new FakeDataSource.Factory().setFakeDataSet(fakeDataSet),
+            masterPlaylistUri,
+            /* awaitedMediaPlaylistCount= */ 2);
+
+    // Finding the media sequence of the second playlist request asserts that the second request has
+    // been made with the correct uri parameter appended.
+    assertThat(mediaPlaylists.get(1).mediaSequence).isEqualTo(11);
+  }
+
+  @Test
+  public void start_playlistCanSkipAndUriWithParams_preservesOriginalParams()
+      throws IOException, TimeoutException {
+    Uri masterPlaylistUri = Uri.parse("fake://foo.bar/master.m3u8");
+    Uri mediaPlaylistUri = Uri.parse("fake://foo.bar/media0/playlist.m3u8?param1=1&param2=2");
+    // Expect _HLS_skip parameter appended with an ampersand.
+    Uri mediaPlaylistSkippedUri = Uri.parse(mediaPlaylistUri + "&_HLS_skip=YES");
+    FakeDataSet fakeDataSet =
+        new FakeDataSet()
+            .setData(masterPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MASTER_MEDIA_URI_WITH_PARAM))
+            .setData(mediaPlaylistUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_UNTIL))
+            .setData(mediaPlaylistSkippedUri, getBytes(SAMPLE_M3U8_LIVE_MEDIA_CAN_SKIP_SKIPPED));
+
+    List<HlsMediaPlaylist> mediaPlaylists =
+        runPlaylistTrackerAndCollectMediaPlaylists(
+            new FakeDataSource.Factory().setFakeDataSet(fakeDataSet),
+            masterPlaylistUri,
+            /* awaitedMediaPlaylistCount= */ 2);
+
+    // Finding the media sequence of the second playlist request asserts that the second request has
+    // been made with the original uri parameters preserved and the additional param concatenated
+    // correctly.
+    assertThat(mediaPlaylists.get(1).mediaSequence).isEqualTo(11);
+  }
+
+  private static List<HlsMediaPlaylist> runPlaylistTrackerAndCollectMediaPlaylists(
+      DataSource.Factory dataSourceFactory, Uri masterPlaylistUri, int awaitedMediaPlaylistCount)
+      throws TimeoutException {
+
+    DefaultHlsPlaylistTracker defaultHlsPlaylistTracker =
+        new DefaultHlsPlaylistTracker(
+            dataType -> dataSourceFactory.createDataSource(),
+            new DefaultLoadErrorHandlingPolicy(),
+            new DefaultHlsPlaylistParserFactory());
+
+    List<HlsMediaPlaylist> mediaPlaylists = new ArrayList<>();
+    AtomicInteger playlistCounter = new AtomicInteger();
+    defaultHlsPlaylistTracker.start(
+        masterPlaylistUri,
+        new MediaSourceEventListener.EventDispatcher(),
+        mediaPlaylist -> {
+          mediaPlaylists.add(mediaPlaylist);
+          playlistCounter.addAndGet(1);
+        });
+
+    RobolectricUtil.runMainLooperUntil(() -> playlistCounter.get() == awaitedMediaPlaylistCount);
+
+    defaultHlsPlaylistTracker.stop();
+    return mediaPlaylists;
+  }
+
+  private static byte[] getBytes(String filename) throws IOException {
+    return TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), filename);
+  }
+
+  private static final class DataSourceList implements DataSource {
+
+    private final DataSource[] dataSources;
+
+    private DataSource delegate;
+    private int index;
+
+    /**
+     * Creates an instance.
+     *
+     * @param dataSources The data sources to delegate to.
+     */
+    public DataSourceList(DataSource... dataSources) {
+      checkArgument(dataSources.length > 0);
+      this.dataSources = dataSources;
+      delegate = dataSources[index++];
+    }
+
+    @Override
+    public void addTransferListener(TransferListener transferListener) {
+      for (DataSource dataSource : dataSources) {
+        dataSource.addTransferListener(transferListener);
+      }
+    }
+
+    @Override
+    public long open(DataSpec dataSpec) throws IOException {
+      checkState(index <= dataSources.length);
+      return delegate.open(dataSpec);
+    }
+
+    @Override
+    public int read(byte[] buffer, int offset, int readLength) throws IOException {
+      return delegate.read(buffer, offset, readLength);
+    }
+
+    @Override
+    @Nullable
+    public Uri getUri() {
+      return delegate.getUri();
+    }
+
+    @Override
+    public Map<String, List<String>> getResponseHeaders() {
+      return delegate.getResponseHeaders();
+    }
+
+    @Override
+    public void close() throws IOException {
+      delegate.close();
+      if (index < dataSources.length) {
+        delegate = dataSources[index];
+      }
+      index++;
+    }
+  }
+}

library/hls/src/test/java/com/google/android/exoplayer2/source/hls/playlist/HlsMediaPlaylistParserTest.java

@@ -299,6 +299,27 @@ public class HlsMediaPlaylistParserTest {
     assertThat(playlist.serverControl.canSkipDateRanges).isTrue();
   }
 
+  @Test
+  public void parseMediaPlaylist_withSkippedSegments_parsesNumberOfSkippedSegments()
+      throws IOException {
+    Uri playlistUri = Uri.parse("https://example.com/test.m3u8");
+    String playlistString =
+        "#EXTM3U\n"
+            + "#EXT-X-TARGETDURATION:4\n"
+            + "#EXT-X-VERSION:6\n"
+            + "#EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24.0\n"
+            + "#EXT-X-MEDIA-SEQUENCE:266\n"
+            + "#EXT-X-SKIP:SKIPPED-SEGMENTS=1234\n"
+            + "#EXTINF:4.00008,\n"
+            + "fileSequence266.mp4";
+    InputStream inputStream = new ByteArrayInputStream(Util.getUtf8Bytes(playlistString));
+
+    HlsMediaPlaylist playlist =
+        (HlsMediaPlaylist) new HlsPlaylistParser().parse(playlistUri, inputStream);
+
+    assertThat(playlist.skippedSegmentCount).isEqualTo(1234);
+  }
+
   @Test
   public void multipleExtXKeysForSingleSegment() throws Exception {
     Uri playlistUri = Uri.parse("https://example.com/test.m3u8");

testdata/src/test/assets/media/m3u8/live_low_latency_master

@@ -0,0 +1,5 @@
+#EXTM3U
+#EXT-X-INDEPENDENT-SEGMENTS
+
+#EXT-X-STREAM-INF:BANDWIDTH=2000000,CODECS="avc1.640028,mp4a.40.2"
+media0/playlist.m3u8

testdata/src/test/assets/media/m3u8/live_low_latency_master_media_uri_with_param

@@ -0,0 +1,5 @@
+#EXTM3U
+#EXT-X-INDEPENDENT-SEGMENTS
+
+#EXT-X-STREAM-INF:BANDWIDTH=2000000,CODECS="avc1.640028,mp4a.40.2"
+media0/playlist.m3u8?param1=1&param2=2

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_not_skip

@@ -0,0 +1,16 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:3
+#EXT-X-MEDIA-SEQUENCE:10
+#EXTINF:4.00000,
+fileSequence10.ts
+#EXTINF:4.00000,
+fileSequence11.ts
+#EXTINF:4.00000,
+fileSequence12.ts
+#EXTINF:4.00000,
+fileSequence13.ts
+#EXTINF:4.00000,
+fileSequence14.ts
+#EXTINF:4.00000,
+fileSequence15.ts

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_not_skip_next

@@ -0,0 +1,16 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:3
+#EXT-X-MEDIA-SEQUENCE:11
+#EXTINF:4.00000,
+fileSequence11.ts
+#EXTINF:4.00000,
+fileSequence12.ts
+#EXTINF:4.00000,
+fileSequence13.ts
+#EXTINF:4.00000,
+fileSequence14.ts
+#EXTINF:4.00000,
+fileSequence15.ts
+#EXTINF:4.00000,
+fileSequence16.ts

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_skip_dateranges

@@ -0,0 +1,17 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:3
+#EXT-X-MEDIA-SEQUENCE:10
+#EXTINF:4.00000,
+fileSequence10.ts
+#EXTINF:4.00000,
+fileSequence11.ts
+#EXTINF:4.00000,
+fileSequence12.ts
+#EXTINF:4.00000,
+fileSequence13.ts
+#EXTINF:4.00000,
+fileSequence14.ts
+#EXTINF:4.00000,
+fileSequence15.ts
+#EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24,CAN-SKIP-DATERANGES=YES

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_skip_skipped

@@ -0,0 +1,14 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:9
+#EXT-X-MEDIA-SEQUENCE:11
+#EXT-X-SKIP:SKIPPED-SEGMENTS=2
+#EXTINF:4.00000,
+fileSequence13.ts
+#EXTINF:4.00000,
+fileSequence14.ts
+#EXTINF:4.00000,
+fileSequence15.ts
+#EXTINF:4.00000,
+fileSequence16.ts
+#EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_skip_skipped_media_sequence_no_overlapping

@@ -0,0 +1,14 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:9
+#EXT-X-MEDIA-SEQUENCE:20
+#EXT-X-SKIP:SKIPPED-SEGMENTS=2
+#EXTINF:4.00000,
+fileSequence22.ts
+#EXTINF:4.00000,
+fileSequence23.ts
+#EXTINF:4.00000,
+fileSequence24.ts
+#EXTINF:4.00000,
+fileSequence25.ts
+#EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24

testdata/src/test/assets/media/m3u8/live_low_latency_media_can_skip_until

@@ -0,0 +1,17 @@
+#EXTM3U
+#EXT-X-TARGETDURATION:4
+#EXT-X-VERSION:3
+#EXT-X-MEDIA-SEQUENCE:10
+#EXTINF:4.00000,
+fileSequence10.ts
+#EXTINF:4.00000,
+fileSequence11.ts
+#EXTINF:4.00000,
+fileSequence12.ts
+#EXTINF:4.00000,
+fileSequence13.ts
+#EXTINF:4.00000,
+fileSequence14.ts
+#EXTINF:4.00000,
+fileSequence15.ts
+#EXT-X-SERVER-CONTROL:CAN-SKIP-UNTIL=24