Report initial discontinuity for DASH periods that require preroll

DASH periods don't have to start at the beginning of a segment. In these cases, they should report an initial discontinuity to let the player know it needs to expect preroll data (e.g. to flush renderers) This information is only available in the ChunkSampleStream after loading the initialization data, so we need to check the sample streams and tell them to only report discontinuities at the very beginning of playback. All other position resets are triggered by the player itself and don't need this method. Issue: androidx/media#1440 PiperOrigin-RevId: 668831563
2025-04-29 22:36:54 +08:00 · 2024-08-29 01:54:10 -07:00 · 2024-08-29 01:54:10 -07:00 · e8664dbc8e
commit e8664dbc8e
parent 8367e420ad
9 changed files with 421 additions and 5 deletions
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@ -101,6 +101,9 @@
 *   Cronet Extension:
 *   RTMP Extension:
 *   HLS Extension:
+*   DASH Extension:
+    *   Add support for periods starting in the middle of a segment
+        ([#1440](https://github.com/androidx/media/issues/1440)).
 *   Smooth Streaming Extension:
 *   RTSP Extension:
 *   Decoder Extensions (FFmpeg, VP9, AV1, etc.):
--- a/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/chunk/ChunkSampleStream.java
+++ b/libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/chunk/ChunkSampleStream.java
@ -22,6 +22,7 @@ import static java.lang.Math.min;
 import androidx.annotation.Nullable;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
+import androidx.media3.common.MimeTypes;
 import androidx.media3.common.util.Assertions;
 import androidx.media3.common.util.Log;
 import androidx.media3.common.util.UnstableApi;
@ -95,6 +96,8 @@ public class ChunkSampleStream<T extends ChunkSource>
  private long lastSeekPositionUs;
  private int nextNotifyPrimaryFormatMediaChunkIndex;
  @Nullable private BaseMediaChunk canceledMediaChunk;
+  private boolean canReportInitialDiscontinuity;
+  private boolean hasInitialDiscontinuity;

  /* package */ boolean loadingFinished;

@ -114,6 +117,8 @@ public class ChunkSampleStream<T extends ChunkSource>
   * @param loadErrorHandlingPolicy The {@link LoadErrorHandlingPolicy}.
   * @param mediaSourceEventDispatcher A dispatcher to notify of {@link MediaSourceEventListener}
   *     events.
+   * @param canReportInitialDiscontinuity Whether the stream can report an initial discontinuity if
+   *     the first chunk can't start at the beginning and needs to preroll data.
   */
  public ChunkSampleStream(
      @C.TrackType int primaryTrackType,
@ -126,7 +131,8 @@ public class ChunkSampleStream<T extends ChunkSource>
      DrmSessionManager drmSessionManager,
      DrmSessionEventListener.EventDispatcher drmEventDispatcher,
      LoadErrorHandlingPolicy loadErrorHandlingPolicy,
-      MediaSourceEventListener.EventDispatcher mediaSourceEventDispatcher) {
+      MediaSourceEventListener.EventDispatcher mediaSourceEventDispatcher,
+      boolean canReportInitialDiscontinuity) {
    this.primaryTrackType = primaryTrackType;
    this.embeddedTrackTypes = embeddedTrackTypes == null ? new int[0] : embeddedTrackTypes;
    this.embeddedTrackFormats = embeddedTrackFormats == null ? new Format[0] : embeddedTrackFormats;
@ -134,6 +140,7 @@ public class ChunkSampleStream<T extends ChunkSource>
    this.callback = callback;
    this.mediaSourceEventDispatcher = mediaSourceEventDispatcher;
    this.loadErrorHandlingPolicy = loadErrorHandlingPolicy;
+    this.canReportInitialDiscontinuity = canReportInitialDiscontinuity;
    loader = new Loader("ChunkSampleStream");
    nextChunkHolder = new ChunkHolder();
    mediaChunks = new ArrayList<>();
@ -258,6 +265,7 @@ public class ChunkSampleStream<T extends ChunkSource>
   */
  public void seekToUs(long positionUs) {
    lastSeekPositionUs = positionUs;
+    canReportInitialDiscontinuity = false;
    if (isPendingReset()) {
      // A reset is already pending. We only need to update its position.
      pendingResetPositionUs = positionUs;
@ -600,12 +608,22 @@ public class ChunkSampleStream<T extends ChunkSource>
        // seeking to a chunk boundary then we want the queue to pass through all of the samples in
        // the chunk. Doing this ensures we'll always output the keyframe at the start of the chunk,
        // even if its timestamp is slightly earlier than the advertised chunk start time.
-        if (mediaChunk.startTimeUs != pendingResetPositionUs) {
+        if (mediaChunk.startTimeUs < pendingResetPositionUs) {
          primarySampleQueue.setStartTimeUs(pendingResetPositionUs);
          for (SampleQueue embeddedSampleQueue : embeddedSampleQueues) {
            embeddedSampleQueue.setStartTimeUs(pendingResetPositionUs);
          }
+          if (canReportInitialDiscontinuity) {
+            // Only report it as discontinuity if the SampleQueue can't skip the samples directly.
+            boolean sampleQueueCanSkipSamples =
+                MimeTypes.allSamplesAreSyncSamples(
+                    mediaChunk.trackFormat.sampleMimeType, mediaChunk.trackFormat.codecs);
+            hasInitialDiscontinuity = !sampleQueueCanSkipSamples;
+          }
        }
+        // Once we started loading the first media chunk, no more initial discontinuities can be
+        // reported.
+        canReportInitialDiscontinuity = false;
        pendingResetPositionUs = C.TIME_UNSET;
      }
      mediaChunk.init(chunkOutput);
@ -670,6 +688,19 @@ public class ChunkSampleStream<T extends ChunkSource>
    }
  }

+  /**
+   * Consumes a pending initial discontinuity.
+   *
+   * @return Whether the stream had an initial discontinuity.
+   */
+  public boolean consumeInitialDiscontinuity() {
+    try {
+      return hasInitialDiscontinuity;
+    } finally {
+      hasInitialDiscontinuity = false;
+    }
+  }
+
  private void discardUpstream(int preferredQueueSize) {
    Assertions.checkState(!loader.isLoading());

--- a/libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/DashMediaPeriod.java
+++ b/libraries/exoplayer_dash/src/main/java/androidx/media3/exoplayer/dash/DashMediaPeriod.java
@ -114,6 +114,8 @@ import java.util.regex.Pattern;
  private DashManifest manifest;
  private int periodIndex;
  private List<EventStream> eventStreams;
+  private boolean canReportInitialDiscontinuity;
+  private long initialStartTimeUs;

  public DashMediaPeriod(
      int id,
@ -149,6 +151,7 @@ import java.util.regex.Pattern;
    this.allocator = allocator;
    this.compositeSequenceableLoaderFactory = compositeSequenceableLoaderFactory;
    this.playerId = playerId;
+    this.canReportInitialDiscontinuity = true;
    playerEmsgHandler = new PlayerEmsgHandler(manifest, playerEmsgCallback, allocator);
    sampleStreams = newSampleStreamArray(0);
    eventSampleStreams = new EventSampleStream[0];
@ -305,6 +308,10 @@ import java.util.regex.Pattern;
        compositeSequenceableLoaderFactory.create(
            sampleStreamList,
            Lists.transform(sampleStreamList, s -> ImmutableList.of(s.primaryTrackType)));
+    if (canReportInitialDiscontinuity) {
+      canReportInitialDiscontinuity = false;
+      initialStartTimeUs = positionUs;
+    }
    return positionUs;
  }

@ -337,6 +344,11 @@ import java.util.regex.Pattern;

  @Override
  public long readDiscontinuity() {
+    for (ChunkSampleStream<DashChunkSource> sampleStream : sampleStreams) {
+      if (sampleStream.consumeInitialDiscontinuity()) {
+        return initialStartTimeUs;
+      }
+    }
    return C.TIME_UNSET;
  }

@ -824,7 +836,8 @@ import java.util.regex.Pattern;
            drmSessionManager,
            drmEventDispatcher,
            loadErrorHandlingPolicy,
-            mediaSourceEventDispatcher);
+            mediaSourceEventDispatcher,
+            canReportInitialDiscontinuity);
    synchronized (this) {
      // The map is also accessed on the loading thread so synchronize access.
      trackEmsgHandlerBySampleStream.put(stream, trackPlayerEmsgHandler);
--- a/libraries/exoplayer_dash/src/test/java/androidx/media3/exoplayer/dash/e2etest/DashPlaybackTest.java
+++ b/libraries/exoplayer_dash/src/test/java/androidx/media3/exoplayer/dash/e2etest/DashPlaybackTest.java
@ -440,4 +440,27 @@ public final class DashPlaybackTest {
    // TODO: b/352276461 - The last frame might not be rendered. When the bug is fixed,
    //  assert on the full playback dump.
  }
+
+  @Test
+  public void multiPeriod_withOffsetInSegment() throws Exception {
+    Context applicationContext = ApplicationProvider.getApplicationContext();
+    CapturingRenderersFactory capturingRenderersFactory =
+        new CapturingRenderersFactory(applicationContext);
+    ExoPlayer player =
+        new ExoPlayer.Builder(applicationContext, capturingRenderersFactory)
+            .setClock(new FakeClock(/* isAutoAdvancing= */ true))
+            .build();
+    player.setVideoSurface(new Surface(new SurfaceTexture(/* texName= */ 1)));
+    PlaybackOutput playbackOutput = PlaybackOutput.register(player, capturingRenderersFactory);
+
+    player.setMediaItem(
+        MediaItem.fromUri("asset:///media/dash/multi-period-with-offset/sample.mpd"));
+    player.prepare();
+    player.play();
+    TestPlayerRunHelper.runUntilPlaybackState(player, Player.STATE_ENDED);
+    player.release();
+
+    DumpFileAsserts.assertOutput(
+        applicationContext, playbackOutput, "playbackdumps/dash/multi-period-with-offset.dump");
+  }
 }
--- a/libraries/exoplayer_smoothstreaming/src/main/java/androidx/media3/exoplayer/smoothstreaming/SsMediaPeriod.java
+++ b/libraries/exoplayer_smoothstreaming/src/main/java/androidx/media3/exoplayer/smoothstreaming/SsMediaPeriod.java
@ -264,7 +264,8 @@ import java.util.List;
        drmSessionManager,
        drmEventDispatcher,
        loadErrorHandlingPolicy,
-        mediaSourceEventDispatcher);
+        mediaSourceEventDispatcher,
+        /* canReportInitialDiscontinuity= */ false);
  }

  private static TrackGroupArray buildTrackGroups(
--- a/libraries/test_data/src/test/assets/media/dash/multi-period-with-offset/sample.mpd
+++ b/libraries/test_data/src/test/assets/media/dash/multi-period-with-offset/sample.mpd
@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 DASH-MPD.xsd" profiles="urn:mpeg:dash:profile:isoff-on-demand:2011" minBufferTime="PT2S" type="static" mediaPresentationDuration="PT1.0010000467300415S">
+  <Period id='0' duration='PT0.5S'>
+    <AdaptationSet id="1" contentType="video" width="1080" height="720" frameRate="30000/1001" subsegmentAlignment="true" par="3:2">
+      <Representation id="1" bandwidth="721967" codecs="avc1.64001f" mimeType="video/mp4" sar="1:1">
+        <BaseURL>sample.video.mp4</BaseURL>
+        <SegmentBase indexRange="862-905" timescale="30000">
+          <Initialization range="0-861"/>
+        </SegmentBase>
+      </Representation>
+    </AdaptationSet>
+  </Period>
+  <Period id='1'>
+      <AdaptationSet id="1" contentType="video" width="1080" height="720" frameRate="30000/1001" subsegmentAlignment="true" par="3:2">
+        <Representation id="1" bandwidth="721967" codecs="avc1.64001f" mimeType="video/mp4" sar="1:1">
+          <BaseURL>sample.video.mp4</BaseURL>
+          <SegmentBase indexRange="862-905" timescale="30000" presentationTimeOffset="15000">
+            <Initialization range="0-861"/>
+          </SegmentBase>
+        </Representation>
+      </AdaptationSet>
+    </Period>
+</MPD>
--- a/libraries/test_data/src/test/assets/media/dash/multi-period-with-offset/sample.video.mp4
+++ b/libraries/test_data/src/test/assets/media/dash/multi-period-with-offset/sample.video.mp4
--- a/libraries/test_data/src/test/assets/playbackdumps/dash/multi-period-with-offset.dump
+++ b/libraries/test_data/src/test/assets/playbackdumps/dash/multi-period-with-offset.dump
@ -0,0 +1,321 @@
+MediaCodecAdapter (exotest.video.avc):
+  inputBuffers:
+    count = 46
+    input buffer #0:
+      timeUs = 1000000000000
+      contents = length 36692, hash D216076E
+    input buffer #1:
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+      contents = length 5312, hash D45D3CA0
+    input buffer #2:
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+      contents = length 599, hash 1BE7812D
+    input buffer #3:
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+      contents = length 7735, hash 4490F110
+    input buffer #4:
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+      contents = length 987, hash 560B5036
+    input buffer #5:
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+    input buffer #6:
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+    input buffer #7:
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+    input buffer #8:
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+    input buffer #9:
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+    input buffer #10:
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+    input buffer #11:
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+    input buffer #12:
+      timeUs = 1000000400400
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+    input buffer #13:
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+      contents = length 620, hash 3990AA39
+    input buffer #14:
+      timeUs = 0
+      flags = 4
+      contents = length 0, hash 1
+    input buffer #15:
+      timeUs = 1000000000000
+      contents = length 36692, hash D216076E
+    input buffer #16:
+      timeUs = 1000000066733
+      contents = length 5312, hash D45D3CA0
+    input buffer #17:
+      timeUs = 1000000033366
+      contents = length 599, hash 1BE7812D
+    input buffer #18:
+      timeUs = 1000000200200
+      contents = length 7735, hash 4490F110
+    input buffer #19:
+      timeUs = 1000000133466
+      contents = length 987, hash 560B5036
+    input buffer #20:
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+    input buffer #21:
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+    input buffer #22:
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+    input buffer #23:
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+    input buffer #24:
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+    input buffer #25:
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+    input buffer #26:
+      timeUs = 1000000433766
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+    input buffer #27:
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+    input buffer #33:
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+    input buffer #35:
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+    input buffer #45:
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+  outputBuffers:
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+      rendered = true
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+      rendered = true
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+      rendered = false
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+      timeUs = 1000000700700
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--- a/libraries/test_utils/src/main/java/androidx/media3/test/utils/FakeAdaptiveMediaPeriod.java
+++ b/libraries/test_utils/src/main/java/androidx/media3/test/utils/FakeAdaptiveMediaPeriod.java
@ -187,7 +187,8 @@ public class FakeAdaptiveMediaPeriod
                DrmSessionManager.DRM_UNSUPPORTED,
                new DrmSessionEventListener.EventDispatcher(),
                new DefaultLoadErrorHandlingPolicy(/* minimumLoadableRetryCount= */ 3),
-                mediaSourceEventDispatcher);
+                mediaSourceEventDispatcher,
+                /* canReportInitialDiscontinuity= */ false);
        streams[i] = sampleStream;
        sampleStreams.add(sampleStream);
        streamResetFlags[i] = true;