DefaultTrackSelector: Constrain audio channel count

The track selector will select multi-channel formats when those can be
spatialized, otherwise the selector will prefer stereo/mono audio
tracks. When the device supports audio spatialization (Android 12L+),
the DefaultTrackSelector will monitor for changes in the platform
Spatializer and trigger a new track selection upon a
Spatializer change event.

Devices with a `television` UI mode are excluded from audio channel
count constraints.

#minor-release

PiperOrigin-RevId: 453957269

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

@@ -369,6 +369,7 @@ import java.util.concurrent.TimeoutException;
       deviceInfo = createDeviceInfo(streamVolumeManager);
       videoSize = VideoSize.UNKNOWN;
 
+      trackSelector.setAudioAttributes(audioAttributes);
       sendRendererMessage(TRACK_TYPE_AUDIO, MSG_SET_AUDIO_SESSION_ID, audioSessionId);
       sendRendererMessage(TRACK_TYPE_VIDEO, MSG_SET_AUDIO_SESSION_ID, audioSessionId);
       sendRendererMessage(TRACK_TYPE_AUDIO, MSG_SET_AUDIO_ATTRIBUTES, audioAttributes);
@@ -1364,6 +1365,7 @@ import java.util.concurrent.TimeoutException;
     }
 
     audioFocusManager.setAudioAttributes(handleAudioFocus ? newAudioAttributes : null);
+    trackSelector.setAudioAttributes(newAudioAttributes);
     boolean playWhenReady = getPlayWhenReady();
     @AudioFocusManager.PlayerCommand
     int playerCommand = audioFocusManager.updateAudioFocus(playWhenReady, getPlaybackState());

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadHelper.java

@@ -107,6 +107,7 @@ public final class DownloadHelper {
           DefaultTrackSelector.Parameters.DEFAULT_WITHOUT_CONTEXT
               .buildUpon()
               .setForceHighestSupportedBitrate(true)
+              .setConstrainAudioChannelCountToDeviceCapabilities(false)
               .build();
 
   /** Returns the default parameters used for track selection for downloading. */
@@ -114,6 +115,7 @@ public final class DownloadHelper {
     return DefaultTrackSelector.Parameters.getDefaults(context)
         .buildUpon()
         .setForceHighestSupportedBitrate(true)
+        .setConstrainAudioChannelCountToDeviceCapabilities(false)
         .build();
   }
 

library/core/src/main/java/com/google/android/exoplayer2/trackselection/TrackSelector.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.trackselection;
 
 import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
 
+import androidx.annotation.CallSuper;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.ExoPlayer;
@@ -25,6 +26,7 @@ import com.google.android.exoplayer2.Renderer;
 import com.google.android.exoplayer2.RendererCapabilities;
 import com.google.android.exoplayer2.RendererConfiguration;
 import com.google.android.exoplayer2.Timeline;
+import com.google.android.exoplayer2.audio.AudioAttributes;
 import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
 import com.google.android.exoplayer2.source.TrackGroupArray;
 import com.google.android.exoplayer2.upstream.BandwidthMeter;
@@ -109,7 +111,8 @@ public abstract class TrackSelector {
    *     it has previously made are no longer valid.
    * @param bandwidthMeter A bandwidth meter which can be used by track selections to select tracks.
    */
-  public final void init(InvalidationListener listener, BandwidthMeter bandwidthMeter) {
+  @CallSuper
+  public void init(InvalidationListener listener, BandwidthMeter bandwidthMeter) {
     this.listener = listener;
     this.bandwidthMeter = bandwidthMeter;
   }
@@ -118,9 +121,10 @@ public abstract class TrackSelector {
    * Called by the player to release the selector. The selector cannot be used until {@link
    * #init(InvalidationListener, BandwidthMeter)} is called again.
    */
-  public final void release() {
-    this.listener = null;
-    this.bandwidthMeter = null;
+  @CallSuper
+  public void release() {
+    listener = null;
+    bandwidthMeter = null;
   }
 
   /**
@@ -175,6 +179,11 @@ public abstract class TrackSelector {
     return false;
   }
 
+  /** Called by the player to set the {@link AudioAttributes} that will be used for playback. */
+  public void setAudioAttributes(AudioAttributes audioAttributes) {
+    // Default implementation is no-op.
+  }
+
   /**
    * Calls {@link InvalidationListener#onTrackSelectionsInvalidated()} to invalidate all previously
    * generated track selections.