google/ExoPlayer · critical · RuntimeException

Error instantiating FLAC extension

Error message

Error instantiating FLAC extension

What it means

DefaultRenderersFactory reflectively loads the optional FLAC decoder renderer (com.google.android.exoplayer2.ext.flac.LibflacAudioRenderer) via its (Handler, AudioRendererEventListener, AudioSink) constructor when extension renderers are enabled. If the class is found but reflection fails (signature mismatch, access failure, or constructor exception), the factory throws a RuntimeException carrying the cause. ClassNotFoundException is the only tolerated outcome because it simply means the extension was not compiled in.

Source

Thrown at library/core/src/main/java/com/google/android/exoplayer2/DefaultRenderersFactory.java:526

    }

    try {
      // Full class names used for constructor args so the LINT rule triggers if any of them move.
      Class<?> clazz = Class.forName("com.google.android.exoplayer2.ext.flac.LibflacAudioRenderer");
      Constructor<?> constructor =
          clazz.getConstructor(
              android.os.Handler.class,
              com.google.android.exoplayer2.audio.AudioRendererEventListener.class,
              com.google.android.exoplayer2.audio.AudioSink.class);
      Renderer renderer =
          (Renderer) constructor.newInstance(eventHandler, eventListener, audioSink);
      out.add(extensionRendererIndex++, renderer);
      Log.i(TAG, "Loaded LibflacAudioRenderer.");
    } catch (ClassNotFoundException e) {
      // Expected if the app was built without the extension.
    } catch (Exception e) {
      // The extension is present, but instantiation failed.
      throw new RuntimeException("Error instantiating FLAC extension", e);
    }

    try {
      // Full class names used for constructor args so the LINT rule triggers if any of them move.
      Class<?> clazz =
          Class.forName("com.google.android.exoplayer2.ext.ffmpeg.FfmpegAudioRenderer");
      Constructor<?> constructor =
          clazz.getConstructor(
              android.os.Handler.class,
              com.google.android.exoplayer2.audio.AudioRendererEventListener.class,
              com.google.android.exoplayer2.audio.AudioSink.class);
      Renderer renderer =
          (Renderer) constructor.newInstance(eventHandler, eventListener, audioSink);
      out.add(extensionRendererIndex++, renderer);
      Log.i(TAG, "Loaded FfmpegAudioRenderer.");
    } catch (ClassNotFoundException e) {
      // Expected if the app was built without the extension.
    } catch (Exception e) {

View on GitHub (pinned to dd430f7053)

Solutions

1. Inspect the chained cause for NoSuchMethodException vs UnsatisfiedLinkError.
2. Use identical versions for exoplayer-core and exoplayer-flac.
3. Keep extension classes intact under R8: -keep class com.google.android.exoplayer2.ext.flac.** { *; }.
4. Drop the extension and let the platform FLAC decoder handle it (Android 3.1+/most devices), i.e. EXTENSION_RENDERER_MODE_OFF.

Example fix

// before
 implementation 'com.google.android.exoplayer:exoplayer:2.19.1'
 implementation 'com.google.android.exoplayer:exoplayer-flac:2.18.1' // version drift!

// after
 implementation 'com.google.android.exoplayer:exoplayer:2.19.1'
 implementation 'com.google.android.exoplayer:exoplayer-flac:2.19.1' // aligned

try {
  Class.forName("com.google.android.exoplayer2.ext.flac.LibflacAudioRenderer")
      .getConstructor(Handler.class, AudioRendererEventListener.class, AudioSink.class);
  // extension structurally present
} catch (ClassNotFoundException e) {
  // not packaged — fine, platform FLAC will be used
} catch (NoSuchMethodException e) {
  // version drift — do not enable extension mode
}

try {
  player = new ExoPlayer.Builder(flacFactory).build(context);
} catch (RuntimeException e) {
  if (e.getMessage() != null && e.getMessage().contains("FLAC extension")) {
    player = new ExoPlayer.Builder(new DefaultRenderersFactory(context)).build(context);
  } else { throw e; }
}

When it happens

Trigger: EXTENSION_RENDERER_MODE_ON/PREFER plus a packaged exoplayer-flac module whose constructor cannot be resolved or whose instantiation throws (missing libflac native library).

Common situations: Mismatched exoplayer-flac and exoplayer-core versions; obfuscated release builds breaking the reflective constructor lookup; APK splits or ABI filters excluding the FLAC native .so; duplicate flac extensions (e.g. both exoplayer-flac and a full exoplayer uber-jar).

Related errors

• Error instantiating Opus extension
• Error instantiating FFmpeg extension
• Error instantiating VP9 extension
• Error instantiating AV1 extension
• Failed to load decoder native libraries.

AI-assisted analysis of google/ExoPlayer@dd430f7053 (2026-08-14). Data as JSON: /api/errors/4e11e172ad69e3b0. Report an issue: GitHub.