Don't recreate the audio decoder if Format is unchanged

More specifically, if the parts of the Format that are used
for decoder configuration are unchanged.

Issue: #2826

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=214791234

library/core/src/main/java/com/google/android/exoplayer2/audio/MediaCodecAudioRenderer.java

@@ -346,7 +346,7 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
     codecMaxInputSize = getCodecMaxInputSize(codecInfo, format, getStreamFormats());
     codecNeedsDiscardChannelsWorkaround = codecNeedsDiscardChannelsWorkaround(codecInfo.name);
     passthroughEnabled = codecInfo.passthrough;
-    String codecMimeType = codecInfo.mimeType == null ? MimeTypes.AUDIO_RAW : codecInfo.mimeType;
+    String codecMimeType = passthroughEnabled ? MimeTypes.AUDIO_RAW : codecInfo.mimeType;
     MediaFormat mediaFormat =
         getMediaFormat(format, codecMimeType, codecMaxInputSize, codecOperatingRate);
     codec.configure(mediaFormat, /* surface= */ null, crypto, /* flags= */ 0);
@@ -362,14 +362,22 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
   @Override
   protected @KeepCodecResult int canKeepCodec(
       MediaCodec codec, MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
-    if (getCodecMaxInputSize(codecInfo, newFormat) <= codecMaxInputSize
+    // TODO: We currently rely on recreating the codec when encoder delay or padding is non-zero.
-        && codecInfo.isSeamlessAdaptationSupported(
+    // Re-creating the codec is necessary to guarantee that onOutputFormatChanged is called, which
-            oldFormat, newFormat, /* isNewFormatComplete= */ true)
+    // is where encoder delay and padding are propagated to the sink. We should find a better way to
-        && oldFormat.encoderDelay == 0
+    // propagate these values, and then allow the codec to be re-used in cases where this would
-        && oldFormat.encoderPadding == 0
+    // otherwise be possible.
-        && newFormat.encoderDelay == 0
+    if (getCodecMaxInputSize(codecInfo, newFormat) > codecMaxInputSize
-        && newFormat.encoderPadding == 0) {
+        || oldFormat.encoderDelay != 0
+        || oldFormat.encoderPadding != 0
+        || newFormat.encoderDelay != 0
+        || newFormat.encoderPadding != 0) {
+      return KEEP_CODEC_RESULT_NO;
+    } else if (codecInfo.isSeamlessAdaptationSupported(
+        oldFormat, newFormat, /* isNewFormatComplete= */ true)) {
       return KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION;
+    } else if (areCodecConfigurationCompatible(oldFormat, newFormat)) {
+      return KEEP_CODEC_RESULT_YES_WITH_FLUSH;
     } else {
       return KEEP_CODEC_RESULT_NO;
     }
@@ -720,6 +728,24 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
     return format.maxInputSize;
   }
 
+  /**
+   * Returns whether two {@link Format}s will cause the same codec to be configured in an identical
+   * way, excluding {@link MediaFormat#KEY_MAX_INPUT_SIZE} and configuration that does not come from
+   * the {@link Format}.
+   *
+   * @param oldFormat The first format.
+   * @param newFormat The second format.
+   * @return Whether the two formats will cause a codec to be configured in an identical way,
+   *     excluding {@link MediaFormat#KEY_MAX_INPUT_SIZE} and configuration that does not come from
+   *     the {@link Format}.
+   */
+  protected boolean areCodecConfigurationCompatible(Format oldFormat, Format newFormat) {
+    return Util.areEqual(oldFormat.sampleMimeType, newFormat.sampleMimeType)
+        && oldFormat.channelCount == newFormat.channelCount
+        && oldFormat.sampleRate == newFormat.sampleRate
+        && oldFormat.initializationDataEquals(newFormat);
+  }
+
   /**
    * Returns the framework {@link MediaFormat} that can be used to configure a {@link MediaCodec}
    * for decoding the given {@link Format} for playback.

library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecRenderer.java

@@ -185,19 +185,22 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
   @Retention(RetentionPolicy.SOURCE)
   @IntDef({
     KEEP_CODEC_RESULT_NO,
-    KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION,
+    KEEP_CODEC_RESULT_YES_WITH_FLUSH,
-    KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION
+    KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION,
+    KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION
   })
   protected @interface KeepCodecResult {}
   /** The codec cannot be kept. */
   protected static final int KEEP_CODEC_RESULT_NO = 0;
-  /** The codec can be kept. No reconfiguration is required. */
+  /** The codec can be kept, but must be flushed. */
-  protected static final int KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION = 1;
+  protected static final int KEEP_CODEC_RESULT_YES_WITH_FLUSH = 1;
   /**
-   * The codec can be kept, but must be reconfigured by prefixing the next input buffer with the new
+   * The codec can be kept. It does not need to be flushed, but must be reconfigured by prefixing
-   * format's configuration data.
+   * the next input buffer with the new format's configuration data.
    */
-  protected static final int KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION = 3;
+  protected static final int KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION = 2;
+  /** The codec can be kept. It does not need to be flushed and no reconfiguration is required. */
+  protected static final int KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION = 3;
 
   @Retention(RetentionPolicy.SOURCE)
   @IntDef({RECONFIGURATION_STATE_NONE, RECONFIGURATION_STATE_WRITE_PENDING,
@@ -309,6 +312,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
   private boolean codecReconfigured;
   private @ReconfigurationState int codecReconfigurationState;
   private @ReinitializationState int codecReinitializationState;
+  private boolean codecReinitializationIsRelease;
   private boolean codecReceivedBuffers;
   private boolean codecReceivedEos;
 
@@ -587,6 +591,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
     codecReceivedEos = false;
     codecReconfigurationState = RECONFIGURATION_STATE_NONE;
     codecReinitializationState = REINITIALIZATION_STATE_NONE;
+    codecReinitializationIsRelease = false;
     codecConfiguredWithOperatingRate = false;
     if (codec != null) {
       decoderCounters.decoderReleaseCount++;
@@ -682,10 +687,16 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
       releaseCodec();
       maybeInitCodec();
     } else if (codecReinitializationState != REINITIALIZATION_STATE_NONE) {
-      // We're already waiting to release and re-initialize the codec. Since we're now flushing,
+      // We're already waiting to re-initialize the codec. Since we're now flushing, there's no need
-      // there's no need to wait any longer.
+      // to wait any longer.
+      if (codecReinitializationIsRelease) {
         releaseCodec();
         maybeInitCodec();
+      } else {
+        codec.flush();
+        codecReceivedBuffers = false;
+        codecReinitializationState = REINITIALIZATION_STATE_NONE;
+      }
     } else {
       // We can flush and re-use the existing decoder.
       codec.flush();
@@ -865,7 +876,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
   private boolean feedInputBuffer() throws ExoPlaybackException {
     if (codec == null || codecReinitializationState == REINITIALIZATION_STATE_WAIT_END_OF_STREAM
         || inputStreamEnded) {
-      // We need to reinitialize the codec or the input stream has ended.
+      // We need to re-initialize the codec or the input stream has ended.
       return false;
     }
 
@@ -1043,7 +1054,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
    * Called when a new format is read from the upstream {@link MediaPeriod}.
    *
    * @param newFormat The new format.
-   * @throws ExoPlaybackException If an error occurs reinitializing the {@link MediaCodec}.
+   * @throws ExoPlaybackException If an error occurs re-initializing the {@link MediaCodec}.
    */
   protected void onInputFormatChanged(Format newFormat) throws ExoPlaybackException {
     Format oldFormat = format;
@@ -1067,18 +1078,28 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
       }
     }
 
-    boolean keepingCodec = false;
+    if (codec == null) {
-    if (pendingDrmSession == drmSession && codec != null) {
+      maybeInitCodec();
+      return;
+    }
+
+    // We have an existing codec that we may need to reconfigure or re-initialize. If the existing
+    // codec instance is being kept then its operating rate may need to be updated.
+    if (pendingDrmSession != drmSession) {
+      reinitializeCodec(/* release= */ true);
+    } else {
       switch (canKeepCodec(codec, codecInfo, oldFormat, format)) {
         case KEEP_CODEC_RESULT_NO:
-          // Do nothing.
+          reinitializeCodec(/* release= */ true);
           break;
-        case KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION:
+        case KEEP_CODEC_RESULT_YES_WITH_FLUSH:
-          keepingCodec = true;
+          reinitializeCodec(/* release= */ false);
+          updateCodecOperatingRate();
           break;
         case KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION:
-          if (!codecNeedsReconfigureWorkaround) {
+          if (codecNeedsReconfigureWorkaround) {
-            keepingCodec = true;
+            reinitializeCodec(/* release= */ true);
+          } else {
             codecReconfigured = true;
             codecReconfigurationState = RECONFIGURATION_STATE_WRITE_PENDING;
             codecNeedsAdaptationWorkaroundBuffer =
@@ -1086,18 +1107,16 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
                     || (codecAdaptationWorkaroundMode == ADAPTATION_WORKAROUND_MODE_SAME_RESOLUTION
                         && format.width == oldFormat.width
                         && format.height == oldFormat.height);
+            updateCodecOperatingRate();
           }
           break;
+        case KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION:
+          updateCodecOperatingRate();
+          break;
         default:
           throw new IllegalStateException(); // Never happens.
       }
     }
-
-    if (!keepingCodec) {
-      reinitializeCodec();
-    } else {
-      updateCodecOperatingRate();
-    }
   }
 
   /**
@@ -1211,13 +1230,15 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
     }
 
     this.codecOperatingRate = codecOperatingRate;
-    if (codec == null || codecReinitializationState != REINITIALIZATION_STATE_NONE) {
+    if (codec == null
-      // Either no codec, or it's about to be reinitialized anyway.
+        || (codecReinitializationState != REINITIALIZATION_STATE_NONE
+            && codecReinitializationIsRelease)) {
+      // Either no codec, or it's about to be released due to re-initialization anyway.
     } else if (codecOperatingRate == CODEC_OPERATING_RATE_UNSET
         && codecConfiguredWithOperatingRate) {
       // We need to clear the operating rate. The only way to do so is to instantiate a new codec
       // instance. See [Internal ref: b/71987865].
-      reinitializeCodec();
+      reinitializeCodec(/* release= */ true);
     } else if (codecOperatingRate != CODEC_OPERATING_RATE_UNSET
         && (codecConfiguredWithOperatingRate
             || codecOperatingRate > assumedMinimumCodecOperatingRate)) {
@@ -1231,18 +1252,26 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
   }
 
   /**
-   * Starts the process of releasing the existing codec and initializing a new one. This may occur
+   * Starts the process of re-initializing the codec. This may occur immediately, or be deferred
-   * immediately, or be deferred until any final output buffers have been dequeued.
+   * until any final output buffers have been dequeued.
    *
+   * @param release Whether re-initialization requires fully releasing the codec and instantiating a
+   *     new instance, as opposed to flushing and reusing the current instance.
    * @throws ExoPlaybackException If an error occurs releasing or initializing a codec.
    */
-  private void reinitializeCodec() throws ExoPlaybackException {
+  private void reinitializeCodec(boolean release) throws ExoPlaybackException {
     availableCodecInfos = null;
     if (codecReceivedBuffers) {
       // Signal end of stream and wait for any final output buffers before re-initialization.
       codecReinitializationState = REINITIALIZATION_STATE_SIGNAL_END_OF_STREAM;
-    } else {
+      codecReinitializationIsRelease = release;
-      // There aren't any final output buffers, so perform re-initialization immediately.
+      return;
+    }
+
+    // Nothing has been queued to the decoder. If we need to fully release the codec and instantiate
+    // a new instance, do so immediately. If only a flush is required then we can do nothing, since
+    // flushing will be a no-op.
+    if (release) {
       releaseCodec();
       maybeInitCodec();
     }
@@ -1449,8 +1478,12 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
   private void processEndOfStream() throws ExoPlaybackException {
     if (codecReinitializationState == REINITIALIZATION_STATE_WAIT_END_OF_STREAM) {
       // We're waiting to re-initialize the codec, and have now processed all final buffers.
+      if (codecReinitializationIsRelease) {
         releaseCodec();
         maybeInitCodec();
+      } else {
+        flushCodec();
+      }
     } else {
       outputStreamEnded = true;
       renderToEndOfStream();