[video_player_android] Implement backBufferDurationMs in ExoPlayer

packages/video_player/video_player_android/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.11.0
+
+* Adds `backBufferDurationMs` to `CreationOptions` to configure ExoPlayer `DefaultLoadControl` back buffer duration.
+
 ## 2.10.0
 
 * Implements `getVideoTracks()` and `selectVideoTrack()` methods for video track (quality) selection using ExoPlayer.

packages/video_player/video_player_android/android/src/main/java/io/flutter/plugins/videoplayer/VideoPlayerOptions.java

@@ -4,6 +4,22 @@
 
 package io.flutter.plugins.videoplayer;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 public class VideoPlayerOptions {
   public boolean mixWithOthers;
+
+  /**
+   * The duration of the back buffer in milliseconds, used to configure ExoPlayer's load control.
+   */
+  @Nullable public Long backBufferDurationMs;
+
+  public VideoPlayerOptions() {}
+
+  /** Copy constructor to ensure all options are reliably copied. */
+  public VideoPlayerOptions(@NonNull VideoPlayerOptions other) {
+    this.mixWithOthers = other.mixWithOthers;
+    this.backBufferDurationMs = other.backBufferDurationMs;
+  }
 }

packages/video_player/video_player_android/android/src/main/java/io/flutter/plugins/videoplayer/VideoPlayerPlugin.java

@@ -87,12 +87,15 @@ public long createForPlatformView(@NonNull CreationOptions options) {
 
     long id = nextPlayerIdentifier++;
     final String streamInstance = Long.toString(id);
+    VideoPlayerOptions playerOptions = new VideoPlayerOptions(sharedOptions);
+    playerOptions.backBufferDurationMs = options.getBackBufferDurationMs();
+
     VideoPlayer videoPlayer =
         PlatformViewVideoPlayer.create(
             flutterState.applicationContext,
             VideoPlayerEventCallbacks.bindTo(flutterState.binaryMessenger, streamInstance),
             videoAsset,
-            sharedOptions);
+            playerOptions);
 
     registerPlayerInstance(videoPlayer, id);
     return id;
@@ -106,13 +109,16 @@ public long createForPlatformView(@NonNull CreationOptions options) {
     long id = nextPlayerIdentifier++;
     final String streamInstance = Long.toString(id);
     TextureRegistry.SurfaceProducer handle = flutterState.textureRegistry.createSurfaceProducer();
+    VideoPlayerOptions playerOptions = new VideoPlayerOptions(sharedOptions);
+    playerOptions.backBufferDurationMs = options.getBackBufferDurationMs();
+
     VideoPlayer videoPlayer =
         TextureVideoPlayer.create(
             flutterState.applicationContext,
             VideoPlayerEventCallbacks.bindTo(flutterState.binaryMessenger, streamInstance),
             handle,
             videoAsset,
-            sharedOptions);
+            playerOptions);
 
     registerPlayerInstance(videoPlayer, id);
     return new TexturePlayerIds(id, handle.id());

packages/video_player/video_player_android/android/src/main/java/io/flutter/plugins/videoplayer/platformview/PlatformViewVideoPlayer.java

@@ -10,6 +10,7 @@
 import androidx.annotation.VisibleForTesting;
 import androidx.media3.common.MediaItem;
 import androidx.media3.common.util.UnstableApi;
+import androidx.media3.exoplayer.DefaultLoadControl;
 import androidx.media3.exoplayer.ExoPlayer;
 import io.flutter.plugins.videoplayer.ExoPlayerEventListener;
 import io.flutter.plugins.videoplayer.VideoAsset;
@@ -56,12 +57,28 @@ public static PlatformViewVideoPlayer create(
         asset.getMediaItem(),
         options,
         () -> {
+          ExoPlayer.Builder builder = new ExoPlayer.Builder(context);
+          if (options.backBufferDurationMs != null) {
+            if (options.backBufferDurationMs < 0) {
+              throw new IllegalArgumentException("backBufferDurationMs must be at least 0");
+            }
+            if (options.backBufferDurationMs > 0) {
+              // Clamp the value to ensure it fits within the int range expected by
+              // DefaultLoadControl.
+              int backBufferInt =
+                  (int) Math.min(options.backBufferDurationMs.longValue(), Integer.MAX_VALUE);
+              DefaultLoadControl loadControl =
+                  new DefaultLoadControl.Builder()
+                      .setBackBuffer(backBufferInt, /* retainBackBufferFromKeyframe= */ true)
+                      .build();
+              builder.setLoadControl(loadControl);
+            }
+          }
           androidx.media3.exoplayer.trackselection.DefaultTrackSelector trackSelector =
               new androidx.media3.exoplayer.trackselection.DefaultTrackSelector(context);
-          ExoPlayer.Builder builder =
-              new ExoPlayer.Builder(context)
-                  .setTrackSelector(trackSelector)
-                  .setMediaSourceFactory(asset.getMediaSourceFactory(context));
+          builder
+              .setTrackSelector(trackSelector)
+              .setMediaSourceFactory(asset.getMediaSourceFactory(context));
           return builder.build();
         });
   }

packages/video_player/video_player_android/android/src/main/java/io/flutter/plugins/videoplayer/texture/TextureVideoPlayer.java

@@ -12,6 +12,7 @@
 import androidx.annotation.VisibleForTesting;
 import androidx.media3.common.MediaItem;
 import androidx.media3.common.util.UnstableApi;
+import androidx.media3.exoplayer.DefaultLoadControl;
 import androidx.media3.exoplayer.ExoPlayer;
 import io.flutter.plugins.videoplayer.ExoPlayerEventListener;
 import io.flutter.plugins.videoplayer.VideoAsset;
@@ -56,12 +57,28 @@ public static TextureVideoPlayer create(
         asset.getMediaItem(),
         options,
         () -> {
+          ExoPlayer.Builder builder = new ExoPlayer.Builder(context);
+          if (options.backBufferDurationMs != null) {
+            if (options.backBufferDurationMs < 0) {
+              throw new IllegalArgumentException("backBufferDurationMs must be at least 0");
+            }
+            if (options.backBufferDurationMs > 0) {
+              // Clamp the value to ensure it fits within the int range expected by
+              // DefaultLoadControl.
+              int backBufferInt =
+                  (int) Math.min(options.backBufferDurationMs.longValue(), Integer.MAX_VALUE);
+              DefaultLoadControl loadControl =
+                  new DefaultLoadControl.Builder()
+                      .setBackBuffer(backBufferInt, /* retainBackBufferFromKeyframe= */ true)
+                      .build();
+              builder.setLoadControl(loadControl);
+            }
+          }
           androidx.media3.exoplayer.trackselection.DefaultTrackSelector trackSelector =
               new androidx.media3.exoplayer.trackselection.DefaultTrackSelector(context);
-          ExoPlayer.Builder builder =
-              new ExoPlayer.Builder(context)
-                  .setTrackSelector(trackSelector)
-                  .setMediaSourceFactory(asset.getMediaSourceFactory(context));
+          builder
+              .setTrackSelector(trackSelector)
+              .setMediaSourceFactory(asset.getMediaSourceFactory(context));
           return builder.build();
         });
   }