Enforce unit speed for ad playback

Ad playback shouldn't be affected by manual speed adjustments set
by the user. This change enforces unit speed for ad playback.

Issue: google/ExoPlayer#9018
PiperOrigin-RevId: 424546258

RELEASENOTES.md

@@ -70,10 +70,12 @@
         When a `DrmSessionManager` is used by an app in a custom `MediaSource`,
         the `playbackLooper` needs to be passed to `DrmSessionManager.setPlayer`
         instead.
-*   IMA:
+*   Ad playback / IMA:
     *   Add a method to `AdPlaybackState` to allow resetting an ad group so that
         it can be played again
         ([#9615](https://github.com/google/ExoPlayer/issues/9615)).
+    *   Enforce playback speed of 1.0 during ad playback
+        ([#9018](https://github.com/google/ExoPlayer/issues/9018)).
 *   DASH:
     *   Support the `forced-subtitle` track role
         ([#9727](https://github.com/google/ExoPlayer/issues/9727)).

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java

@@ -1913,9 +1913,12 @@ import java.util.concurrent.atomic.AtomicBoolean;
       MediaPeriodId oldPeriodId,
       long positionForTargetOffsetOverrideUs) {
     if (!shouldUseLivePlaybackSpeedControl(newTimeline, newPeriodId)) {
-      // Live playback speed control is unused for the current period, reset speed if adjusted.
-      if (!mediaClock.getPlaybackParameters().equals(playbackInfo.playbackParameters)) {
-        mediaClock.setPlaybackParameters(playbackInfo.playbackParameters);
+      // Live playback speed control is unused for the current period, reset speed to user-defined
+      // playback parameters or 1.0 for ad playback.
+      PlaybackParameters targetPlaybackParameters =
+          newPeriodId.isAd() ? PlaybackParameters.DEFAULT : playbackInfo.playbackParameters;
+      if (!mediaClock.getPlaybackParameters().equals(targetPlaybackParameters)) {
+        mediaClock.setPlaybackParameters(targetPlaybackParameters);
       }
       return;
     }

library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java

@@ -9325,6 +9325,85 @@ public final class ExoPlayerTest {
   }
 
   @Test
+  public void setPlaybackSpeed_withAdPlayback_onlyAppliesToContent() throws Exception {
+    // Create renderer with media clock to listen to playback parameter changes.
+    ArrayList<PlaybackParameters> playbackParameters = new ArrayList<>();
+    FakeMediaClockRenderer audioRenderer =
+        new FakeMediaClockRenderer(C.TRACK_TYPE_AUDIO) {
+          private long positionUs;
+
+          @Override
+          protected void onStreamChanged(Format[] formats, long startPositionUs, long offsetUs) {
+            this.positionUs = offsetUs;
+          }
+
+          @Override
+          public long getPositionUs() {
+            // Continuously increase position to let playback progress.
+            positionUs += 10_000;
+            return positionUs;
+          }
+
+          @Override
+          public void setPlaybackParameters(PlaybackParameters parameters) {
+            playbackParameters.add(parameters);
+          }
+
+          @Override
+          public PlaybackParameters getPlaybackParameters() {
+            return playbackParameters.isEmpty()
+                ? PlaybackParameters.DEFAULT
+                : Iterables.getLast(playbackParameters);
+          }
+        };
+    ExoPlayer player = new TestExoPlayerBuilder(context).setRenderers(audioRenderer).build();
+    AdPlaybackState adPlaybackState =
+        FakeTimeline.createAdPlaybackState(
+            /* adsPerAdGroup= */ 1,
+            /* adGroupTimesUs...= */ 0,
+            7 * C.MICROS_PER_SECOND,
+            C.TIME_END_OF_SOURCE);
+    TimelineWindowDefinition adTimelineDefinition =
+        new TimelineWindowDefinition(
+            /* periodCount= */ 1,
+            /* id= */ 0,
+            /* isSeekable= */ true,
+            /* isDynamic= */ false,
+            /* isLive= */ false,
+            /* isPlaceholder= */ false,
+            /* durationUs= */ 10 * C.MICROS_PER_SECOND,
+            /* defaultPositionUs= */ 0,
+            /* windowOffsetInFirstPeriodUs= */ 0,
+            adPlaybackState);
+    player.setMediaSource(
+        new FakeMediaSource(
+            new FakeTimeline(adTimelineDefinition), ExoPlayerTestRunner.AUDIO_FORMAT));
+    Player.Listener mockListener = mock(Player.Listener.class);
+    player.addListener(mockListener);
+
+    player.setPlaybackSpeed(5f);
+    player.prepare();
+    player.play();
+    runUntilPlaybackState(player, Player.STATE_ENDED);
+    player.release();
+
+    // Assert that the renderer received the playback speed updates at each ad/content boundary.
+    assertThat(playbackParameters)
+        .containsExactly(
+            /* preroll ad */ new PlaybackParameters(1f),
+            /* content after preroll */ new PlaybackParameters(5f),
+            /* midroll ad */ new PlaybackParameters(1f),
+            /* content after midroll */ new PlaybackParameters(5f),
+            /* postroll ad */ new PlaybackParameters(1f),
+            /* content after postroll */ new PlaybackParameters(5f))
+        .inOrder();
+
+    // Assert that user-set speed was reported, but none of the ad overrides.
+    verify(mockListener).onPlaybackParametersChanged(any());
+    verify(mockListener).onPlaybackParametersChanged(new PlaybackParameters(5.0f));
+  }
+
+  @Test
   public void targetLiveOffsetInMedia_withSetPlaybackParameters_usesPlaybackParameterSpeed()
       throws Exception {
     long windowStartUnixTimeMs = 987_654_321_000L;