Seek at a chunk level when seeking to chunk start positions

RELEASENOTES.md

@@ -23,6 +23,8 @@
 *   Cronet Extension:
 *   RTMP Extension:
 *   HLS Extension:
+    *   Resolve seeks to beginning of a segment more efficiently
+        ([#1031](https://github.com/androidx/media/pull/1031)).
 *   DASH Extension:
 *   Smooth Streaming Extension:
 *   RTSP Extension:

libraries/exoplayer_hls/src/main/java/androidx/media3/exoplayer/hls/HlsChunkSource.java

@@ -242,6 +242,11 @@ public TrackGroup getTrackGroup() {
     return trackGroup;
   }
 
+  /** Returns whether the chunk source has independent segments. */
+  public boolean hasIndependentSegments() {
+    return independentSegments;
+  }
+
   /**
    * Sets the current track selection.
    *

libraries/exoplayer_hls/src/main/java/androidx/media3/exoplayer/hls/HlsSampleStreamWrapper.java

@@ -496,8 +496,21 @@ public boolean seekToUs(long positionUs, boolean forceReset) {
       return true;
     }
 
+    // Detect whether the seek is to the start of a chunk that's at least partially buffered.
+    @Nullable HlsMediaChunk seekToMediaChunk = null;
+    if (chunkSource.hasIndependentSegments()) {
+      for (int i = 0; i < mediaChunks.size(); i++) {
+        HlsMediaChunk mediaChunk = mediaChunks.get(i);
+        long mediaChunkStartTimeUs = mediaChunk.startTimeUs;
+        if (mediaChunkStartTimeUs == positionUs) {
+          seekToMediaChunk = mediaChunk;
+          break;
+        }
+      }
+    }
+
     // If we're not forced to reset, try and seek within the buffer.
-    if (sampleQueuesBuilt && !forceReset && seekInsideBufferUs(positionUs)) {
+    if (sampleQueuesBuilt && !forceReset && seekInsideBufferUs(positionUs, seekToMediaChunk)) {
       return false;
     }
 
@@ -1470,13 +1483,20 @@ private boolean isPendingReset() {
    * Attempts to seek to the specified position within the sample queues.
    *
    * @param positionUs The seek position in microseconds.
+   * @param chunk The chunk to seek to, or null to seek to the exact position. {@code positionUs} is
+   *     ignored if this is non-null.
    * @return Whether the in-buffer seek was successful.
    */
-  private boolean seekInsideBufferUs(long positionUs) {
+  private boolean seekInsideBufferUs(long positionUs, @Nullable HlsMediaChunk chunk) {
     int sampleQueueCount = sampleQueues.length;
     for (int i = 0; i < sampleQueueCount; i++) {
       SampleQueue sampleQueue = sampleQueues[i];
-      boolean seekInsideQueue = sampleQueue.seekTo(positionUs, /* allowTimeBeyondBuffer= */ false);
+      boolean seekInsideQueue;
+      if (chunk != null) {
+        seekInsideQueue = sampleQueue.seekTo(chunk.getFirstSampleIndex(i));
+      } else {
+        seekInsideQueue = sampleQueue.seekTo(positionUs, /* allowTimeBeyondBuffer= */ false);
+      }
       // If we have AV tracks then an in-queue seek is successful if the seek into every AV queue
       // is successful. We ignore whether seeks within non-AV queues are successful in this case, as
       // they may be sparse or poorly interleaved. If we only have non-AV tracks then a seek is

libraries/exoplayer_hls/src/test/java/androidx/media3/exoplayer/hls/e2etest/HlsPlaybackTest.java

@@ -23,6 +23,7 @@
 import androidx.media3.common.Player;
 import androidx.media3.datasource.DefaultDataSource;
 import androidx.media3.exoplayer.ExoPlayer;
+import androidx.media3.exoplayer.SeekParameters;
 import androidx.media3.exoplayer.hls.HlsMediaSource;
 import androidx.media3.test.utils.CapturingRenderersFactory;
 import androidx.media3.test.utils.DumpFileAsserts;
@@ -153,4 +154,37 @@ public void cea608_parseDuringExtraction() throws Exception {
     DumpFileAsserts.assertOutput(
         applicationContext, playbackOutput, "playbackdumps/hls/cea608.dump");
   }
+
+  @Test
+  public void multiSegment_withSeekToPrevSyncFrame_startsRenderingAtBeginningOfSegment()
+      throws Exception {
+    Context applicationContext = ApplicationProvider.getApplicationContext();
+    CapturingRenderersFactory capturingRenderersFactory =
+        new CapturingRenderersFactory(applicationContext);
+    ExoPlayer player =
+        new ExoPlayer.Builder(applicationContext, capturingRenderersFactory)
+            .setMediaSourceFactory(
+                new HlsMediaSource.Factory(new DefaultDataSource.Factory(applicationContext))
+                    .experimentalParseSubtitlesDuringExtraction(true))
+            .setClock(new FakeClock(/* isAutoAdvancing= */ true))
+            .build();
+    // Prepare media fully to ensure we have all the segment data available.
+    player.setVideoSurface(new Surface(new SurfaceTexture(/* texName= */ 1)));
+    PlaybackOutput playbackOutput = PlaybackOutput.register(player, capturingRenderersFactory);
+    player.setMediaItem(MediaItem.fromUri("asset:///media/hls/multi-segment/playlist.m3u8"));
+    player.prepare();
+    TestPlayerRunHelper.runUntilIsLoading(player, true);
+    TestPlayerRunHelper.runUntilIsLoading(player, false);
+
+    // Seek to beginning of second segment (at 500ms according to playlist)
+    player.setSeekParameters(SeekParameters.PREVIOUS_SYNC);
+    player.seekTo(600);
+    player.play();
+    TestPlayerRunHelper.runUntilPlaybackState(player, Player.STATE_ENDED);
+    player.release();
+
+    // Output only starts at 550ms (the first sample in the second segment)
+    DumpFileAsserts.assertOutput(
+        applicationContext, playbackOutput, "playbackdumps/hls/multi-segment-with-seek.dump");
+  }
 }

libraries/test_data/src/test/assets/media/hls/multi-segment/playlist.m3u8

@@ -0,0 +1,11 @@
+#EXTM3U
+#EXT-X-VERSION:7
+#EXT-X-TARGETDURATION:1
+#EXT-X-MEDIA-SEQUENCE:0
+#EXT-X-INDEPENDENT-SEGMENTS
+#EXT-X-MAP:URI="init.mp4"
+#EXTINF:0.500,
+playlist0.m4s
+#EXTINF:0.550,
+playlist1.m4s
+#EXT-X-ENDLIST