Fix Dackka/Metalava errors in av1, flac, ffmpeg, midi, and opus modules

This uses `@hide` on `protected final` methods to hide them from Dackka
javadoc generation, since these methods are inaccessible to developers
anyway. These symbols will still (currently) be included in artefacts
distributed on Maven (because we don't run Metalava as part of
generating these artefacts).

In some cases I had to change the visibility/finality of methods to make
them `protected final` before adding the `@hide` annotation (but
the impact should be very low, since most of these methods were either
already unusable by app developers, or they shouldn't have been used).

#minor-release

PiperOrigin-RevId: 487472907

extensions/av1/src/main/java/com/google/android/exoplayer2/ext/av1/Libgav1VideoRenderer.java

@@ -138,8 +138,13 @@ public String getName() {
         C.FORMAT_HANDLED, ADAPTIVE_SEAMLESS, TUNNELING_NOT_SUPPORTED);
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * @hide
+   */
   @Override
-  protected Gav1Decoder createDecoder(Format format, @Nullable CryptoConfig cryptoConfig)
+  protected final Gav1Decoder createDecoder(Format format, @Nullable CryptoConfig cryptoConfig)
       throws Gav1DecoderException {
     TraceUtil.beginSection("createGav1Decoder");
     int initialInputBufferSize =

extensions/ffmpeg/src/main/java/com/google/android/exoplayer2/ext/ffmpeg/FfmpegAudioRenderer.java

@@ -104,10 +104,15 @@ public String getName() {
   }
 
   @Override
-  public final @AdaptiveSupport int supportsMixedMimeTypeAdaptation() {
+  public @AdaptiveSupport int supportsMixedMimeTypeAdaptation() {
     return ADAPTIVE_NOT_SEAMLESS;
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * @hide
+   */
   @Override
   protected FfmpegAudioDecoder createDecoder(Format format, @Nullable CryptoConfig cryptoConfig)
       throws FfmpegDecoderException {
@@ -121,8 +126,13 @@ protected FfmpegAudioDecoder createDecoder(Format format, @Nullable CryptoConfig
     return decoder;
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * @hide
+   */
   @Override
-  public Format getOutputFormat(FfmpegAudioDecoder decoder) {
+  protected Format getOutputFormat(FfmpegAudioDecoder decoder) {
     Assertions.checkNotNull(decoder);
     return new Format.Builder()
         .setSampleMimeType(MimeTypes.AUDIO_RAW)

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/LibflacAudioRenderer.java

@@ -106,6 +106,11 @@ public String getName() {
     }
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * @hide
+   */
   @Override
   protected FlacDecoder createDecoder(Format format, @Nullable CryptoConfig cryptoConfig)
       throws FlacDecoderException {
@@ -116,6 +121,11 @@ protected FlacDecoder createDecoder(Format format, @Nullable CryptoConfig crypto
     return decoder;
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * @hide
+   */
   @Override
   protected Format getOutputFormat(FlacDecoder decoder) {
     return getOutputFormat(decoder.getStreamMetadata());

extensions/opus/src/main/java/com/google/android/exoplayer2/ext/opus/LibopusAudioRenderer.java

@@ -93,8 +93,13 @@ public String getName() {
     }
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * @hide
+   */
   @Override
-  protected OpusDecoder createDecoder(Format format, @Nullable CryptoConfig cryptoConfig)
+  protected final OpusDecoder createDecoder(Format format, @Nullable CryptoConfig cryptoConfig)
       throws OpusDecoderException {
     TraceUtil.beginSection("createOpusDecoder");
     @SinkFormatSupport
@@ -119,8 +124,13 @@ protected OpusDecoder createDecoder(Format format, @Nullable CryptoConfig crypto
     return decoder;
   }
 
+  /**
+   * {@inheritDoc} g
+   *
+   * @hide
+   */
   @Override
-  protected Format getOutputFormat(OpusDecoder decoder) {
+  protected final Format getOutputFormat(OpusDecoder decoder) {
     @C.PcmEncoding
     int pcmEncoding = decoder.outputFloat ? C.ENCODING_PCM_FLOAT : C.ENCODING_PCM_16BIT;
     return Util.getPcmFormat(pcmEncoding, decoder.channelCount, OpusDecoder.SAMPLE_RATE);