Report reasons for not being able to reuse decoders

PiperOrigin-RevId: 342344090

RELEASENOTES.md

@@ -48,6 +48,12 @@
 *   DRM:
     *   Fix playback failure when switching from PlayReady protected content to
         Widevine or Clearkey protected content in a playlist.
+*   Analytics:
+    *   Pass a `DecoderReuseEvaluation` to `AnalyticsListener`'s
+        `onVideoInputFormatChanged` and `onAudioInputFormatChanged` methods. The
+        `DecoderReuseEvaluation` indicates whether it was possible to re-use an
+        existing decoder instance for the new format, and if not then the
+        reasons why.
 *   IMA extension:
     *   Upgrade IMA SDK dependency to 3.21.0, and release the `AdsLoader`
         ([#7344](https://github.com/google/ExoPlayer/issues/7344)).

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

@@ -15,12 +15,15 @@
  */
 package com.google.android.exoplayer2.ext.av1;
 
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITHOUT_RECONFIGURATION;
+
 import android.os.Handler;
 import android.view.Surface;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.RendererCapabilities;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.TraceUtil;
@@ -164,7 +167,13 @@ public class Libgav1VideoRenderer extends DecoderVideoRenderer {
   }
 
   @Override
-  protected boolean canKeepCodec(Format oldFormat, Format newFormat) {
+  protected DecoderReuseEvaluation canReuseDecoder(
-    return true;
+      String decoderName, Format oldFormat, Format newFormat) {
+    return new DecoderReuseEvaluation(
+        decoderName,
+        oldFormat,
+        newFormat,
+        REUSE_RESULT_YES_WITHOUT_RECONFIGURATION,
+        /* discardReasons= */ 0);
   }
 }

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

@@ -15,6 +15,10 @@
  */
 package com.google.android.exoplayer2.ext.ffmpeg;
 
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_MIME_TYPE_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITHOUT_RECONFIGURATION;
+
 import android.os.Handler;
 import android.view.Surface;
 import androidx.annotation.Nullable;
@@ -22,6 +26,7 @@ import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.RendererCapabilities;
 import com.google.android.exoplayer2.decoder.Decoder;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
 import com.google.android.exoplayer2.util.TraceUtil;
 import com.google.android.exoplayer2.util.Util;
@@ -116,7 +121,15 @@ public final class FfmpegVideoRenderer extends DecoderVideoRenderer {
   }
 
   @Override
-  protected boolean canKeepCodec(Format oldFormat, Format newFormat) {
+  protected DecoderReuseEvaluation canReuseDecoder(
-    return Util.areEqual(oldFormat.sampleMimeType, newFormat.sampleMimeType);
+      String decoderName, Format oldFormat, Format newFormat) {
+    boolean sameMimeType = Util.areEqual(oldFormat.sampleMimeType, newFormat.sampleMimeType);
+    // TODO: Ability to reuse the decoder may be MIME type dependent.
+    return new DecoderReuseEvaluation(
+        decoderName,
+        oldFormat,
+        newFormat,
+        sameMimeType ? REUSE_RESULT_YES_WITHOUT_RECONFIGURATION : REUSE_RESULT_NO,
+        sameMimeType ? 0 : DISCARD_REASON_MIME_TYPE_CHANGED);
   }
 }

extensions/vp9/src/main/java/com/google/android/exoplayer2/ext/vp9/LibvpxVideoRenderer.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.ext.vp9;
 
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITHOUT_RECONFIGURATION;
 import static java.lang.Runtime.getRuntime;
 
 import android.os.Handler;
@@ -23,6 +24,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.RendererCapabilities;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.TraceUtil;
@@ -169,7 +171,13 @@ public class LibvpxVideoRenderer extends DecoderVideoRenderer {
   }
 
   @Override
-  protected boolean canKeepCodec(Format oldFormat, Format newFormat) {
+  protected DecoderReuseEvaluation canReuseDecoder(
-    return true;
+      String decoderName, Format oldFormat, Format newFormat) {
+    return new DecoderReuseEvaluation(
+        decoderName,
+        oldFormat,
+        newFormat,
+        REUSE_RESULT_YES_WITHOUT_RECONFIGURATION,
+        /* discardReasons= */ 0);
   }
 }

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

@@ -36,6 +36,7 @@ import com.google.android.exoplayer2.audio.AudioListener;
 import com.google.android.exoplayer2.audio.AudioRendererEventListener;
 import com.google.android.exoplayer2.audio.AuxEffectInfo;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.device.DeviceInfo;
 import com.google.android.exoplayer2.device.DeviceListener;
 import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory;
@@ -2242,10 +2243,11 @@ public class SimpleExoPlayer extends BasePlayer
     }
 
     @Override
-    public void onVideoInputFormatChanged(Format format) {
+    public void onVideoInputFormatChanged(
+        Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
       videoFormat = format;
       for (VideoRendererEventListener videoDebugListener : videoDebugListeners) {
-        videoDebugListener.onVideoInputFormatChanged(format);
+        videoDebugListener.onVideoInputFormatChanged(format, decoderReuseEvaluation);
       }
     }
 
@@ -2337,10 +2339,11 @@ public class SimpleExoPlayer extends BasePlayer
     }
 
     @Override
-    public void onAudioInputFormatChanged(Format format) {
+    public void onAudioInputFormatChanged(
+        Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
       audioFormat = format;
       for (AudioRendererEventListener audioDebugListener : audioDebugListeners) {
-        audioDebugListener.onAudioInputFormatChanged(format);
+        audioDebugListener.onAudioInputFormatChanged(format, decoderReuseEvaluation);
       }
     }
 

library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java

@@ -34,6 +34,7 @@ import com.google.android.exoplayer2.audio.AudioAttributes;
 import com.google.android.exoplayer2.audio.AudioListener;
 import com.google.android.exoplayer2.audio.AudioRendererEventListener;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.drm.DrmSessionEventListener;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.MetadataOutput;
@@ -195,11 +196,12 @@ public class AnalyticsCollector
 
   @SuppressWarnings("deprecation")
   @Override
-  public final void onAudioInputFormatChanged(Format format) {
+  public final void onAudioInputFormatChanged(
+      Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
     EventTime eventTime = generateReadingMediaPeriodEventTime();
     listeners.sendEvent(
         listener -> {
-          listener.onAudioInputFormatChanged(eventTime, format);
+          listener.onAudioInputFormatChanged(eventTime, format, decoderReuseEvaluation);
           listener.onDecoderInputFormatChanged(eventTime, C.TRACK_TYPE_AUDIO, format);
         });
   }
@@ -298,11 +300,12 @@ public class AnalyticsCollector
 
   @SuppressWarnings("deprecation")
   @Override
-  public final void onVideoInputFormatChanged(Format format) {
+  public final void onVideoInputFormatChanged(
+      Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
     EventTime eventTime = generateReadingMediaPeriodEventTime();
     listeners.sendEvent(
         listener -> {
-          listener.onVideoInputFormatChanged(eventTime, format);
+          listener.onVideoInputFormatChanged(eventTime, format, decoderReuseEvaluation);
           listener.onDecoderInputFormatChanged(eventTime, C.TRACK_TYPE_VIDEO, format);
         });
   }

library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsListener.java

@@ -30,6 +30,7 @@ import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.audio.AudioAttributes;
 import com.google.android.exoplayer2.audio.AudioSink;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.source.LoadEventInfo;
 import com.google.android.exoplayer2.source.MediaLoadData;
@@ -452,8 +453,8 @@ public interface AnalyticsListener {
       EventTime eventTime, int trackType, String decoderName, long initializationDurationMs) {}
 
   /**
-   * @deprecated Use {@link #onAudioInputFormatChanged} and {@link #onVideoInputFormatChanged}
+   * @deprecated Use {@link #onAudioInputFormatChanged(EventTime, Format, DecoderReuseEvaluation)}
-   *     instead.
+   *     and {@link #onVideoInputFormatChanged(EventTime, Format, DecoderReuseEvaluation)}. instead.
    */
   @Deprecated
   default void onDecoderInputFormatChanged(EventTime eventTime, int trackType, Format format) {}
@@ -482,13 +483,26 @@ public interface AnalyticsListener {
   default void onAudioDecoderInitialized(
       EventTime eventTime, String decoderName, long initializationDurationMs) {}
 
+  /**
+   * @deprecated Use {@link #onAudioInputFormatChanged(EventTime, Format, DecoderReuseEvaluation)}.
+   */
+  @Deprecated
+  default void onAudioInputFormatChanged(EventTime eventTime, Format format) {}
+
   /**
    * Called when the format of the media being consumed by an audio renderer changes.
    *
    * @param eventTime The event time.
    * @param format The new format.
+   * @param decoderReuseEvaluation The result of the evaluation to determine whether an existing
+   *     decoder instance can be reused for the new format, or {@code null} if the renderer did not
+   *     have a decoder.
    */
-  default void onAudioInputFormatChanged(EventTime eventTime, Format format) {}
+  @SuppressWarnings("deprecation")
+  default void onAudioInputFormatChanged(
+      EventTime eventTime, Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
+    onAudioInputFormatChanged(eventTime, format);
+  }
 
   /**
    * Called when the audio position has increased for the first time since the last pause or
@@ -589,13 +603,26 @@ public interface AnalyticsListener {
   default void onVideoDecoderInitialized(
       EventTime eventTime, String decoderName, long initializationDurationMs) {}
 
+  /**
+   * @deprecated Use {@link #onVideoInputFormatChanged(EventTime, Format, DecoderReuseEvaluation)}.
+   */
+  @Deprecated
+  default void onVideoInputFormatChanged(EventTime eventTime, Format format) {}
+
   /**
    * Called when the format of the media being consumed by a video renderer changes.
    *
    * @param eventTime The event time.
    * @param format The new format.
+   * @param decoderReuseEvaluation The result of the evaluation to determine whether an existing
+   *     decoder instance can be reused for the new format, or {@code null} if the renderer did not
+   *     have a decoder.
    */
-  default void onVideoInputFormatChanged(EventTime eventTime, Format format) {}
+  @SuppressWarnings("deprecation")
+  default void onVideoInputFormatChanged(
+      EventTime eventTime, Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
+    onVideoInputFormatChanged(eventTime, format);
+  }
 
   /**
    * Called after video frames have been dropped.

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

@@ -27,6 +27,7 @@ import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Renderer;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.util.Assertions;
 
 /**
@@ -61,12 +62,23 @@ public interface AudioRendererEventListener {
   default void onAudioDecoderInitialized(
       String decoderName, long initializedTimestampMs, long initializationDurationMs) {}
 
+  /** @deprecated Use {@link #onAudioInputFormatChanged(Format, DecoderReuseEvaluation)}. */
+  @Deprecated
+  default void onAudioInputFormatChanged(Format format) {}
+
   /**
    * Called when the format of the media being consumed by the renderer changes.
    *
    * @param format The new format.
+   * @param decoderReuseEvaluation The result of the evaluation to determine whether an existing
+   *     decoder instance can be reused for the new format, or {@code null} if the renderer did not
+   *     have a decoder.
    */
-  default void onAudioInputFormatChanged(Format format) {}
+  @SuppressWarnings("deprecation")
+  default void onAudioInputFormatChanged(
+      Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
+    onAudioInputFormatChanged(format);
+  }
 
   /**
    * Called when the audio position has increased for the first time since the last pause or
@@ -167,9 +179,11 @@ public interface AudioRendererEventListener {
     }
 
     /** Invokes {@link AudioRendererEventListener#onAudioInputFormatChanged(Format)}. */
-    public void inputFormatChanged(Format format) {
+    public void inputFormatChanged(
+        Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
       if (handler != null) {
-        handler.post(() -> castNonNull(listener).onAudioInputFormatChanged(format));
+        handler.post(
+            () -> castNonNull(listener).onAudioInputFormatChanged(format, decoderReuseEvaluation));
       }
     }
 

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

@@ -15,6 +15,9 @@
  */
 package com.google.android.exoplayer2.audio;
 
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_DRM_SESSION_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_REUSE_NOT_IMPLEMENTED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
 import static java.lang.Math.max;
 
 import android.media.audiofx.Virtualizer;
@@ -38,6 +41,7 @@ import com.google.android.exoplayer2.decoder.Decoder;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
 import com.google.android.exoplayer2.decoder.DecoderException;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.decoder.SimpleOutputBuffer;
 import com.google.android.exoplayer2.drm.DrmSession;
 import com.google.android.exoplayer2.drm.DrmSession.DrmSessionException;
@@ -347,14 +351,19 @@ public abstract class DecoderAudioRenderer<
   protected abstract Format getOutputFormat(T decoder);
 
   /**
-   * Returns whether the existing decoder can be kept for a new format.
+   * Evaluates whether the existing decoder can be reused for a new {@link Format}.
    *
+   * <p>The default implementation does not allow decoder reuse.
+   *
+   * @param decoderName The name of the decoder.
    * @param oldFormat The previous format.
    * @param newFormat The new format.
-   * @return Whether the existing decoder can be kept.
+   * @return The result of the evaluation.
    */
-  protected boolean canKeepCodec(Format oldFormat, Format newFormat) {
+  protected DecoderReuseEvaluation canReuseDecoder(
-    return false;
+      String decoderName, Format oldFormat, Format newFormat) {
+    return new DecoderReuseEvaluation(
+        decoderName, oldFormat, newFormat, REUSE_RESULT_NO, DISCARD_REASON_REUSE_NOT_IMPLEMENTED);
   }
 
   private boolean drainOutputBuffer()
@@ -655,10 +664,29 @@ public abstract class DecoderAudioRenderer<
     setSourceDrmSession(formatHolder.drmSession);
     Format oldFormat = inputFormat;
     inputFormat = newFormat;
+    encoderDelay = newFormat.encoderDelay;
+    encoderPadding = newFormat.encoderPadding;
 
     if (decoder == null) {
       maybeInitDecoder();
-    } else if (sourceDrmSession != decoderDrmSession || !canKeepCodec(oldFormat, inputFormat)) {
+      eventDispatcher.inputFormatChanged(inputFormat, /* decoderReuseEvaluation= */ null);
+      return;
+    }
+
+    DecoderReuseEvaluation evaluation;
+    if (sourceDrmSession != decoderDrmSession) {
+      evaluation =
+          new DecoderReuseEvaluation(
+              decoder.getName(),
+              oldFormat,
+              newFormat,
+              REUSE_RESULT_NO,
+              DISCARD_REASON_DRM_SESSION_CHANGED);
+    } else {
+      evaluation = canReuseDecoder(decoder.getName(), oldFormat, newFormat);
+    }
+
+    if (evaluation.result == REUSE_RESULT_NO) {
       if (decoderReceivedBuffers) {
         // Signal end of stream and wait for any final output buffers before re-initialization.
         decoderReinitializationState = REINITIALIZATION_STATE_SIGNAL_END_OF_STREAM;
@@ -669,10 +697,7 @@ public abstract class DecoderAudioRenderer<
         audioTrackNeedsConfigure = true;
       }
     }
-
+    eventDispatcher.inputFormatChanged(inputFormat, evaluation);
-    encoderDelay = inputFormat.encoderDelay;
-    encoderPadding = inputFormat.encoderPadding;
-    eventDispatcher.inputFormatChanged(inputFormat);
   }
 
   private void onQueueInputBuffer(DecoderInputBuffer buffer) {

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

@@ -15,7 +15,8 @@
  */
 package com.google.android.exoplayer2.audio;
 
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_MAX_INPUT_SIZE_EXCEEDED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
 import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
 import static java.lang.Math.max;
 
@@ -41,9 +42,10 @@ import com.google.android.exoplayer2.audio.AudioRendererEventListener.EventDispa
 import com.google.android.exoplayer2.audio.AudioSink.InitializationException;
 import com.google.android.exoplayer2.audio.AudioSink.WriteException;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DecoderDiscardReasons;
 import com.google.android.exoplayer2.mediacodec.MediaCodecAdapter;
 import com.google.android.exoplayer2.mediacodec.MediaCodecInfo;
-import com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KeepCodecResult;
 import com.google.android.exoplayer2.mediacodec.MediaCodecRenderer;
 import com.google.android.exoplayer2.mediacodec.MediaCodecSelector;
 import com.google.android.exoplayer2.mediacodec.MediaCodecUtil;
@@ -328,13 +330,21 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
   }
 
   @Override
-  @KeepCodecResult
+  protected DecoderReuseEvaluation canReuseCodec(
-  protected int canKeepCodec(
+      MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
-      MediaCodecAdapter codec, MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
+    DecoderReuseEvaluation evaluation = codecInfo.canReuseCodec(oldFormat, newFormat);
+
+    @DecoderDiscardReasons int discardReasons = evaluation.discardReasons;
     if (getCodecMaxInputSize(codecInfo, newFormat) > codecMaxInputSize) {
-      return KEEP_CODEC_RESULT_NO;
+      discardReasons |= DISCARD_REASON_MAX_INPUT_SIZE_EXCEEDED;
     }
-    return codecInfo.canKeepCodec(oldFormat, newFormat);
+
+    return new DecoderReuseEvaluation(
+        codecInfo.name,
+        oldFormat,
+        newFormat,
+        discardReasons != 0 ? REUSE_RESULT_NO : evaluation.result,
+        discardReasons);
   }
 
   @Override
@@ -370,9 +380,12 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
   }
 
   @Override
-  protected void onInputFormatChanged(FormatHolder formatHolder) throws ExoPlaybackException {
+  @Nullable
-    super.onInputFormatChanged(formatHolder);
+  protected DecoderReuseEvaluation onInputFormatChanged(FormatHolder formatHolder)
-    eventDispatcher.inputFormatChanged(formatHolder.format);
+      throws ExoPlaybackException {
+    @Nullable DecoderReuseEvaluation evaluation = super.onInputFormatChanged(formatHolder);
+    eventDispatcher.inputFormatChanged(formatHolder.format, evaluation);
+    return evaluation;
   }
 
   @Override
@@ -664,7 +677,7 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
       return maxInputSize;
     }
     for (Format streamFormat : streamFormats) {
-      if (codecInfo.canKeepCodec(format, streamFormat) != KEEP_CODEC_RESULT_NO) {
+      if (codecInfo.canReuseCodec(format, streamFormat).result != REUSE_RESULT_NO) {
         maxInputSize = max(maxInputSize, getCodecMaxInputSize(codecInfo, streamFormat));
       }
     }

library/core/src/main/java/com/google/android/exoplayer2/decoder/DecoderReuseEvaluation.java

@@ -0,0 +1,178 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.decoder;
+
+import static com.google.android.exoplayer2.util.Assertions.checkArgument;
+import static com.google.android.exoplayer2.util.Assertions.checkNotEmpty;
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
+
+import androidx.annotation.IntDef;
+import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.video.ColorInfo;
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * The result of an evaluation to determine whether a decoder can be reused for a new input format.
+ */
+public final class DecoderReuseEvaluation {
+
+  /** Possible outcomes of the evaluation. */
+  @Documented
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef({
+    REUSE_RESULT_NO,
+    REUSE_RESULT_YES_WITH_FLUSH,
+    REUSE_RESULT_YES_WITH_RECONFIGURATION,
+    REUSE_RESULT_YES_WITHOUT_RECONFIGURATION
+  })
+  public @interface DecoderReuseResult {}
+  /** The decoder cannot be reused. */
+  public static final int REUSE_RESULT_NO = 0;
+  /** The decoder can be reused, but must be flushed. */
+  public static final int REUSE_RESULT_YES_WITH_FLUSH = 1;
+  /**
+   * The decoder can be reused. It does not need to be flushed, but must be reconfigured by
+   * prefixing the next input buffer with the new format's configuration data.
+   */
+  public static final int REUSE_RESULT_YES_WITH_RECONFIGURATION = 2;
+  /** The decoder can be kept. It does not need to be flushed and no reconfiguration is required. */
+  public static final int REUSE_RESULT_YES_WITHOUT_RECONFIGURATION = 3;
+
+  /** Possible reasons why reuse is not possible. */
+  @Documented
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef(
+      flag = true,
+      value = {
+        DISCARD_REASON_REUSE_NOT_IMPLEMENTED,
+        DISCARD_REASON_WORKAROUND,
+        DISCARD_REASON_APP_OVERRIDE,
+        DISCARD_REASON_MIME_TYPE_CHANGED,
+        DISCARD_REASON_OPERATING_RATE_CHANGED,
+        DISCARD_REASON_INITIALIZATION_DATA_CHANGED,
+        DISCARD_REASON_DRM_SESSION_CHANGED,
+        DISCARD_REASON_MAX_INPUT_SIZE_EXCEEDED,
+        DISCARD_REASON_VIDEO_MAX_RESOLUTION_EXCEEDED,
+        DISCARD_REASON_VIDEO_RESOLUTION_CHANGED,
+        DISCARD_REASON_VIDEO_ROTATION_CHANGED,
+        DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED,
+        DISCARD_REASON_AUDIO_CHANNEL_COUNT_CHANGED,
+        DISCARD_REASON_AUDIO_SAMPLE_RATE_CHANGED,
+        DISCARD_REASON_AUDIO_ENCODING_CHANGED
+      })
+  public @interface DecoderDiscardReasons {}
+
+  /** Decoder reuse is not implemented. */
+  public static final int DISCARD_REASON_REUSE_NOT_IMPLEMENTED = 1 << 0;
+  /** Decoder reuse is disabled by a workaround. */
+  public static final int DISCARD_REASON_WORKAROUND = 1 << 1;
+  /** Decoder reuse is disabled by overriding behavior in application code. */
+  public static final int DISCARD_REASON_APP_OVERRIDE = 1 << 2;
+  /** The sample MIME type is changing. */
+  public static final int DISCARD_REASON_MIME_TYPE_CHANGED = 1 << 3;
+  /** The codec's operating rate is changing. */
+  public static final int DISCARD_REASON_OPERATING_RATE_CHANGED = 1 << 4;
+  /** The format initialization data is changing. */
+  public static final int DISCARD_REASON_INITIALIZATION_DATA_CHANGED = 1 << 5;
+  /** The new format may exceed the decoder's configured maximum sample size, in bytes. */
+  public static final int DISCARD_REASON_MAX_INPUT_SIZE_EXCEEDED = 1 << 6;
+  /** The DRM session is changing. */
+  public static final int DISCARD_REASON_DRM_SESSION_CHANGED = 1 << 7;
+  /** The new format may exceed the decoder's configured maximum resolution. */
+  public static final int DISCARD_REASON_VIDEO_MAX_RESOLUTION_EXCEEDED = 1 << 8;
+  /** The video resolution is changing. */
+  public static final int DISCARD_REASON_VIDEO_RESOLUTION_CHANGED = 1 << 9;
+  /** The video rotation is changing. */
+  public static final int DISCARD_REASON_VIDEO_ROTATION_CHANGED = 1 << 10;
+  /** The video {@link ColorInfo} is changing. */
+  public static final int DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED = 1 << 11;
+  /** The audio channel count is changing. */
+  public static final int DISCARD_REASON_AUDIO_CHANNEL_COUNT_CHANGED = 1 << 12;
+  /** The audio sample rate is changing. */
+  public static final int DISCARD_REASON_AUDIO_SAMPLE_RATE_CHANGED = 1 << 13;
+  /** The audio encoding is changing. */
+  public static final int DISCARD_REASON_AUDIO_ENCODING_CHANGED = 1 << 14;
+
+  /** The name of the decoder. */
+  public final String decoderName;
+
+  /** The {@link Format} for which the decoder was previously configured. */
+  public final Format oldFormat;
+
+  /** The new {@link Format} being evaluated. */
+  public final Format newFormat;
+
+  /** The {@link DecoderReuseResult result} of the evaluation. */
+  @DecoderReuseResult public final int result;
+
+  /**
+   * {@link DecoderDiscardReasons Reasons} why the decoder cannot be reused. Always {@code 0} if
+   * reuse is possible. May also be {code 0} if reuse is not possible for an unspecified reason.
+   */
+  @DecoderDiscardReasons public final int discardReasons;
+
+  /**
+   * @param decoderName The name of the decoder.
+   * @param oldFormat The {@link Format} for which the decoder was previously configured.
+   * @param newFormat The new {@link Format} being evaluated.
+   * @param result The {@link DecoderReuseResult result} of the evaluation.
+   * @param discardReasons One or more {@link DecoderDiscardReasons reasons} why the decoder cannot
+   *     be reused, or {@code 0} if reuse is possible.
+   */
+  public DecoderReuseEvaluation(
+      String decoderName,
+      Format oldFormat,
+      Format newFormat,
+      @DecoderReuseResult int result,
+      @DecoderDiscardReasons int discardReasons) {
+    checkArgument(result == REUSE_RESULT_NO || discardReasons == 0);
+    this.decoderName = checkNotEmpty(decoderName);
+    this.oldFormat = checkNotNull(oldFormat);
+    this.newFormat = checkNotNull(newFormat);
+    this.result = result;
+    this.discardReasons = discardReasons;
+  }
+
+  @Override
+  public boolean equals(@Nullable Object obj) {
+    if (this == obj) {
+      return true;
+    }
+    if (obj == null || getClass() != obj.getClass()) {
+      return false;
+    }
+    DecoderReuseEvaluation other = (DecoderReuseEvaluation) obj;
+    return result == other.result
+        && discardReasons == other.discardReasons
+        && decoderName.equals(other.decoderName)
+        && oldFormat.equals(other.oldFormat)
+        && newFormat.equals(other.newFormat);
+  }
+
+  @Override
+  public int hashCode() {
+    int hashCode = 17;
+    hashCode = 31 * hashCode + result;
+    hashCode = 31 * hashCode + discardReasons;
+    hashCode = 31 * hashCode + decoderName.hashCode();
+    hashCode = 31 * hashCode + oldFormat.hashCode();
+    hashCode = 31 * hashCode + newFormat.hashCode();
+    return hashCode;
+  }
+}

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

@@ -15,6 +15,20 @@
  */
 package com.google.android.exoplayer2.mediacodec;
 
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_AUDIO_CHANNEL_COUNT_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_AUDIO_ENCODING_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_AUDIO_SAMPLE_RATE_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_INITIALIZATION_DATA_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_MIME_TYPE_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_RESOLUTION_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_ROTATION_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_WORKAROUND;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITHOUT_RECONFIGURATION;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITH_FLUSH;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITH_RECONFIGURATION;
+
 import android.graphics.Point;
 import android.media.MediaCodec;
 import android.media.MediaCodecInfo.AudioCapabilities;
@@ -22,18 +36,17 @@ import android.media.MediaCodecInfo.CodecCapabilities;
 import android.media.MediaCodecInfo.CodecProfileLevel;
 import android.media.MediaCodecInfo.VideoCapabilities;
 import android.util.Pair;
-import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.annotation.VisibleForTesting;
 import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DecoderDiscardReasons;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DecoderReuseResult;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.Util;
-import java.lang.annotation.Documented;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
 
 /** Information about a {@link MediaCodec} for a given mime type. */
 @SuppressWarnings("InlinedApi")
@@ -47,28 +60,6 @@ public final class MediaCodecInfo {
    */
   public static final int MAX_SUPPORTED_INSTANCES_UNKNOWN = -1;
 
-  /** The possible return values for {@link #canKeepCodec(Format, Format)}. */
-  @Documented
-  @Retention(RetentionPolicy.SOURCE)
-  @IntDef({
-    KEEP_CODEC_RESULT_NO,
-    KEEP_CODEC_RESULT_YES_WITH_FLUSH,
-    KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION,
-    KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION
-  })
-  public @interface KeepCodecResult {}
-  /** The codec cannot be kept. */
-  public static final int KEEP_CODEC_RESULT_NO = 0;
-  /** The codec can be kept, but must be flushed. */
-  public static final int KEEP_CODEC_RESULT_YES_WITH_FLUSH = 1;
-  /**
-   * The codec can be kept. It does not need to be flushed, but must be reconfigured by prefixing
-   * the next input buffer with the new format's configuration data.
-   */
-  public 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. */
-  public static final int KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION = 3;
-
   /**
    * The name of the decoder.
    *
@@ -361,7 +352,7 @@ public final class MediaCodecInfo {
    * @param isNewFormatComplete Whether {@code newFormat} is populated with format-specific
    *     metadata.
    * @return Whether it is possible to adapt the decoder seamlessly.
-   * @deprecated Use {@link #canKeepCodec}.
+   * @deprecated Use {@link #canReuseCodec}.
    */
   @Deprecated
   public boolean isSeamlessAdaptationSupported(
@@ -369,49 +360,68 @@ public final class MediaCodecInfo {
     if (!isNewFormatComplete && oldFormat.colorInfo != null && newFormat.colorInfo == null) {
       newFormat = newFormat.buildUpon().setColorInfo(oldFormat.colorInfo).build();
     }
-    @KeepCodecResult int keepCodecResult = canKeepCodec(oldFormat, newFormat);
+    @DecoderReuseResult int reuseResult = canReuseCodec(oldFormat, newFormat).result;
-    return keepCodecResult == KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION
+    return reuseResult == REUSE_RESULT_YES_WITH_RECONFIGURATION
-        || keepCodecResult == KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION;
+        || reuseResult == REUSE_RESULT_YES_WITHOUT_RECONFIGURATION;
   }
 
   /**
-   * Returns the extent to which it's possible to adapt an instance of this decoder that's currently
+   * Evaluates whether it's possible to reuse an instance of this decoder that's currently decoding
-   * decoding {@code oldFormat} to decode {@code newFormat} instead.
+   * {@code oldFormat} to decode {@code newFormat} instead.
    *
    * <p>For adaptation to succeed, the codec must also be configured with maximum values that are
    * compatible with the new format.
    *
    * @param oldFormat The format being decoded.
    * @param newFormat The new format.
-   * @return The extent to which it's possible to adapt an instance of the decoder.
+   * @return The result of the evaluation.
    */
-  @KeepCodecResult
+  public DecoderReuseEvaluation canReuseCodec(Format oldFormat, Format newFormat) {
-  public int canKeepCodec(Format oldFormat, Format newFormat) {
+    @DecoderDiscardReasons int discardReasons = 0;
     if (!Util.areEqual(oldFormat.sampleMimeType, newFormat.sampleMimeType)) {
-      return KEEP_CODEC_RESULT_NO;
+      discardReasons |= DISCARD_REASON_MIME_TYPE_CHANGED;
     }
 
     if (isVideo) {
-      if (oldFormat.rotationDegrees == newFormat.rotationDegrees
+      if (oldFormat.rotationDegrees != newFormat.rotationDegrees) {
-          && (adaptive
+        discardReasons |= DISCARD_REASON_VIDEO_ROTATION_CHANGED;
-              || (oldFormat.width == newFormat.width && oldFormat.height == newFormat.height))
+      }
-          && Util.areEqual(oldFormat.colorInfo, newFormat.colorInfo)) {
+      if (!adaptive
-        if (oldFormat.initializationDataEquals(newFormat)) {
+          && (oldFormat.width != newFormat.width || oldFormat.height != newFormat.height)) {
-          return KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION;
+        discardReasons |= DISCARD_REASON_VIDEO_RESOLUTION_CHANGED;
-        } else if (!needsAdaptationReconfigureWorkaround(name)) {
+      }
-          return KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION;
+      if (!Util.areEqual(oldFormat.colorInfo, newFormat.colorInfo)) {
-        }
+        discardReasons |= DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED;
+      }
+      if (needsAdaptationReconfigureWorkaround(name)
+          && !oldFormat.initializationDataEquals(newFormat)) {
+        discardReasons |= DISCARD_REASON_WORKAROUND;
+      }
+
+      if (discardReasons == 0) {
+        return new DecoderReuseEvaluation(
+            name,
+            oldFormat,
+            newFormat,
+            oldFormat.initializationDataEquals(newFormat)
+                ? REUSE_RESULT_YES_WITHOUT_RECONFIGURATION
+                : REUSE_RESULT_YES_WITH_RECONFIGURATION,
+            /* discardReasons= */ 0);
       }
     } else {
-      if (oldFormat.channelCount != newFormat.channelCount
+      if (oldFormat.channelCount != newFormat.channelCount) {
-          || oldFormat.sampleRate != newFormat.sampleRate
+        discardReasons |= DISCARD_REASON_AUDIO_CHANNEL_COUNT_CHANGED;
-          || oldFormat.pcmEncoding != newFormat.pcmEncoding) {
+      }
-        return KEEP_CODEC_RESULT_NO;
+      if (oldFormat.sampleRate != newFormat.sampleRate) {
+        discardReasons |= DISCARD_REASON_AUDIO_SAMPLE_RATE_CHANGED;
+      }
+      if (oldFormat.pcmEncoding != newFormat.pcmEncoding) {
+        discardReasons |= DISCARD_REASON_AUDIO_ENCODING_CHANGED;
       }
 
       // Check whether we're adapting between two xHE-AAC formats, for which adaptation is possible
       // without reconfiguration or flushing.
-      if (MimeTypes.AUDIO_AAC.equals(mimeType)) {
+      if (discardReasons == 0 && MimeTypes.AUDIO_AAC.equals(mimeType)) {
         @Nullable
         Pair<Integer, Integer> oldCodecProfileLevel =
             MediaCodecUtil.getCodecProfileAndLevel(oldFormat);
@@ -423,18 +433,30 @@ public final class MediaCodecInfo {
           int newProfile = newCodecProfileLevel.first;
           if (oldProfile == CodecProfileLevel.AACObjectXHE
               && newProfile == CodecProfileLevel.AACObjectXHE) {
-            return KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION;
+            return new DecoderReuseEvaluation(
+                name,
+                oldFormat,
+                newFormat,
+                REUSE_RESULT_YES_WITHOUT_RECONFIGURATION,
+                /* discardReasons= */ 0);
           }
         }
       }
 
-      if (oldFormat.initializationDataEquals(newFormat)
+      if (!oldFormat.initializationDataEquals(newFormat)) {
-          && !needsAdaptationFlushWorkaround(mimeType)) {
+        discardReasons |= DISCARD_REASON_INITIALIZATION_DATA_CHANGED;
-        return KEEP_CODEC_RESULT_YES_WITH_FLUSH;
+      }
+      if (needsAdaptationFlushWorkaround(mimeType)) {
+        discardReasons |= DISCARD_REASON_WORKAROUND;
+      }
+
+      if (discardReasons == 0) {
+        return new DecoderReuseEvaluation(
+            name, oldFormat, newFormat, REUSE_RESULT_YES_WITH_FLUSH, /* discardReasons= */ 0);
       }
     }
 
-    return KEEP_CODEC_RESULT_NO;
+    return new DecoderReuseEvaluation(name, oldFormat, newFormat, REUSE_RESULT_NO, discardReasons);
   }
 
   /**

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

@@ -15,10 +15,14 @@
  */
 package com.google.android.exoplayer2.mediacodec;
 
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_DRM_SESSION_CHANGED;
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_OPERATING_RATE_CHANGED;
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_YES_WITH_FLUSH;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_REUSE_NOT_IMPLEMENTED;
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_WORKAROUND;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITHOUT_RECONFIGURATION;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITH_FLUSH;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITH_RECONFIGURATION;
 import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
 import static com.google.android.exoplayer2.util.Assertions.checkState;
 import static java.lang.Math.max;
@@ -44,11 +48,12 @@ import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.FormatHolder;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DecoderDiscardReasons;
 import com.google.android.exoplayer2.drm.DrmSession;
 import com.google.android.exoplayer2.drm.DrmSession.DrmSessionException;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
 import com.google.android.exoplayer2.drm.FrameworkMediaCrypto;
-import com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KeepCodecResult;
 import com.google.android.exoplayer2.mediacodec.MediaCodecUtil.DecoderQueryException;
 import com.google.android.exoplayer2.source.MediaPeriod;
 import com.google.android.exoplayer2.source.SampleStream;
@@ -710,7 +715,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
     if (codec != null
         && codecDrainAction != DRAIN_ACTION_REINITIALIZE
         && getState() != STATE_DISABLED) {
-      updateOperatingRateOrReinitializeCodec(codecInputFormat);
+      updateCodecOperatingRate(codecInputFormat);
     }
   }
 
@@ -1375,9 +1380,13 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
    *
    * @param formatHolder A {@link FormatHolder} that holds the new {@link Format}.
    * @throws ExoPlaybackException If an error occurs re-initializing the {@link MediaCodec}.
+   * @return The result of the evaluation to determine whether the existing decoder instance can be
+   *     reused for the new format, or {@code null} if the renderer did not have a decoder.
    */
   @CallSuper
-  protected void onInputFormatChanged(FormatHolder formatHolder) throws ExoPlaybackException {
+  @Nullable
+  protected DecoderReuseEvaluation onInputFormatChanged(FormatHolder formatHolder)
+      throws ExoPlaybackException {
     waitingForFirstSampleInFormat = true;
     Format newFormat = checkNotNull(formatHolder.format);
     setSourceDrmSession(formatHolder.drmSession);
@@ -1385,7 +1394,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
 
     if (bypassEnabled) {
       bypassDrainAndReinitialize = true;
-      return; // Need to drain batch buffer first.
+      return null; // Need to drain batch buffer first.
     }
 
     if (codec == null) {
@@ -1393,66 +1402,86 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
         availableCodecInfos = null;
       }
       maybeInitCodecOrBypass();
-      return;
+      return null;
     }
 
     // We have an existing codec that we may need to reconfigure, re-initialize, or release to
     // switch to bypass. If the existing codec instance is kept then its operating rate and DRM
     // session may need to be updated.
-
+    MediaCodecAdapter oldCodec = codec;
+    Format oldFormat = codecInputFormat;
     if (drmNeedsCodecReinitialization(codecInfo, newFormat, codecDrmSession, sourceDrmSession)) {
       drainAndReinitializeCodec();
-      return;
+      return new DecoderReuseEvaluation(
+          codecInfo.name,
+          oldFormat,
+          newFormat,
+          REUSE_RESULT_NO,
+          DISCARD_REASON_DRM_SESSION_CHANGED);
     }
     boolean drainAndUpdateCodecDrmSession = sourceDrmSession != codecDrmSession;
     Assertions.checkState(!drainAndUpdateCodecDrmSession || Util.SDK_INT >= 23);
 
-    switch (canKeepCodec(codec, codecInfo, codecInputFormat, newFormat)) {
+    DecoderReuseEvaluation evaluation = canReuseCodec(codecInfo, oldFormat, newFormat);
-      case KEEP_CODEC_RESULT_NO:
+    @DecoderDiscardReasons int overridingDiscardReasons = 0;
+    switch (evaluation.result) {
+      case REUSE_RESULT_NO:
         drainAndReinitializeCodec();
         break;
-      case KEEP_CODEC_RESULT_YES_WITH_FLUSH:
+      case REUSE_RESULT_YES_WITH_FLUSH:
-        if (updateOperatingRateOrReinitializeCodec(newFormat)) {
+        if (!updateCodecOperatingRate(newFormat)) {
-          // Codec re-initialization triggered.
+          overridingDiscardReasons |= DISCARD_REASON_OPERATING_RATE_CHANGED;
         } else {
           codecInputFormat = newFormat;
           if (drainAndUpdateCodecDrmSession) {
-            drainAndUpdateCodecDrmSessionV23();
+            if (!drainAndUpdateCodecDrmSessionV23()) {
-          } else {
+              overridingDiscardReasons |= DISCARD_REASON_WORKAROUND;
-            drainAndFlushCodec();
+            }
+          } else if (!drainAndFlushCodec()) {
+            overridingDiscardReasons |= DISCARD_REASON_WORKAROUND;
           }
         }
         break;
-      case KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION:
+      case REUSE_RESULT_YES_WITH_RECONFIGURATION:
-        if (updateOperatingRateOrReinitializeCodec(newFormat)) {
+        if (!updateCodecOperatingRate(newFormat)) {
-          // Codec re-initialization triggered.
+          overridingDiscardReasons |= DISCARD_REASON_OPERATING_RATE_CHANGED;
         } else {
           codecReconfigured = true;
           codecReconfigurationState = RECONFIGURATION_STATE_WRITE_PENDING;
           codecNeedsAdaptationWorkaroundBuffer =
               codecAdaptationWorkaroundMode == ADAPTATION_WORKAROUND_MODE_ALWAYS
                   || (codecAdaptationWorkaroundMode == ADAPTATION_WORKAROUND_MODE_SAME_RESOLUTION
-                      && newFormat.width == codecInputFormat.width
+                      && newFormat.width == oldFormat.width
-                      && newFormat.height == codecInputFormat.height);
+                      && newFormat.height == oldFormat.height);
           codecInputFormat = newFormat;
-          if (drainAndUpdateCodecDrmSession) {
+          if (drainAndUpdateCodecDrmSession && !drainAndUpdateCodecDrmSessionV23()) {
-            drainAndUpdateCodecDrmSessionV23();
+            overridingDiscardReasons |= DISCARD_REASON_WORKAROUND;
           }
         }
         break;
-      case KEEP_CODEC_RESULT_YES_WITHOUT_RECONFIGURATION:
+      case REUSE_RESULT_YES_WITHOUT_RECONFIGURATION:
-        if (updateOperatingRateOrReinitializeCodec(newFormat)) {
+        if (!updateCodecOperatingRate(newFormat)) {
-          // Codec re-initialization triggered.
+          overridingDiscardReasons |= DISCARD_REASON_OPERATING_RATE_CHANGED;
         } else {
           codecInputFormat = newFormat;
-          if (drainAndUpdateCodecDrmSession) {
+          if (drainAndUpdateCodecDrmSession && !drainAndUpdateCodecDrmSessionV23()) {
-            drainAndUpdateCodecDrmSessionV23();
+            overridingDiscardReasons |= DISCARD_REASON_WORKAROUND;
           }
         }
         break;
       default:
         throw new IllegalStateException(); // Never happens.
     }
+
+    if (evaluation.result != REUSE_RESULT_NO
+        && (codec != oldCodec || codecDrainAction == DRAIN_ACTION_REINITIALIZE)) {
+      // Initial evaluation indicated reuse was possible, but codec re-initialization was triggered.
+      // The reasons are indicated by overridingDiscardReasons.
+      return new DecoderReuseEvaluation(
+          codecInfo.name, oldFormat, newFormat, REUSE_RESULT_NO, overridingDiscardReasons);
+    }
+
+    return evaluation;
   }
 
   /**
@@ -1544,21 +1573,24 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
   }
 
   /**
-   * Determines whether the existing {@link MediaCodec} can be kept for a new {@link Format}, and if
+   * Evaluates whether the existing {@link MediaCodec} can be kept for a new {@link Format}, and if
    * it can whether it requires reconfiguration.
    *
-   * <p>The default implementation returns {@link MediaCodecInfo#KEEP_CODEC_RESULT_NO}.
+   * <p>The default implementation does not allow decoder reuse.
    *
-   * @param codec The existing {@link MediaCodecAdapter} instance.
    * @param codecInfo A {@link MediaCodecInfo} describing the decoder.
    * @param oldFormat The {@link Format} for which the existing instance is configured.
    * @param newFormat The new {@link Format}.
-   * @return Whether the instance can be kept, and if it can whether it requires reconfiguration.
+   * @return The result of the evaluation.
    */
-  @KeepCodecResult
+  protected DecoderReuseEvaluation canReuseCodec(
-  protected int canKeepCodec(
+      MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
-      MediaCodecAdapter codec, MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
+    return new DecoderReuseEvaluation(
-    return KEEP_CODEC_RESULT_NO;
+        codecInfo.name,
+        oldFormat,
+        newFormat,
+        REUSE_RESULT_NO,
+        DISCARD_REASON_REUSE_NOT_IMPLEMENTED);
   }
 
   @Override
@@ -1608,25 +1640,23 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
    *
    * @param format The {@link Format} for which the operating rate should be configured.
    * @throws ExoPlaybackException If an error occurs releasing or initializing a codec.
-   * @return Whether codec release and re-initialization was triggered, rather than the existing
+   * @return False if codec release and re-initialization was triggered. True in all other cases.
-   *     codec being updated.
    */
-  private boolean updateOperatingRateOrReinitializeCodec(Format format)
+  private boolean updateCodecOperatingRate(Format format) throws ExoPlaybackException {
-      throws ExoPlaybackException {
     if (Util.SDK_INT < 23) {
-      return false;
+      return true;
     }
 
     float newCodecOperatingRate =
         getCodecOperatingRateV23(playbackSpeed, format, getStreamFormats());
     if (codecOperatingRate == newCodecOperatingRate) {
       // No change.
-      return false;
+      return true;
     } else if (newCodecOperatingRate == CODEC_OPERATING_RATE_UNSET) {
       // The only way to clear the operating rate is to instantiate a new codec instance. See
       // [Internal ref: b/111543954].
       drainAndReinitializeCodec();
-      return true;
+      return false;
     } else if (codecOperatingRate != CODEC_OPERATING_RATE_UNSET
         || newCodecOperatingRate > assumedMinimumCodecOperatingRate) {
       // We need to set the operating rate, either because we've set it previously or because it's
@@ -1635,36 +1665,48 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
       codecParameters.putFloat(MediaFormat.KEY_OPERATING_RATE, newCodecOperatingRate);
       codec.setParameters(codecParameters);
       codecOperatingRate = newCodecOperatingRate;
-      return false;
+      return true;
     }
 
-    return false;
+    return true;
   }
 
-  /** Starts draining the codec for flush. */
+  /**
-  private void drainAndFlushCodec() {
+   * Starts draining the codec for a flush, or to release and re-initialize the codec if flushing
+   * will not be possible. If no buffers have been queued to the codec then this method is a no-op.
+   *
+   * @return False if codec release and re-initialization was triggered due to the need to apply a
+   *     flush workaround. True in all other cases.
+   */
+  private boolean drainAndFlushCodec() {
     if (codecReceivedBuffers) {
       codecDrainState = DRAIN_STATE_SIGNAL_END_OF_STREAM;
       if (codecNeedsFlushWorkaround || codecNeedsEosFlushWorkaround) {
         codecDrainAction = DRAIN_ACTION_REINITIALIZE;
+        return false;
       } else {
         codecDrainAction = DRAIN_ACTION_FLUSH;
       }
     }
+    return true;
   }
 
   /**
-   * Starts draining the codec to update its DRM session. The update may occur immediately if no
+   * Starts draining the codec to flush it and update its DRM session, or to release and
-   * buffers have been queued to the codec.
+   * re-initialize the codec if flushing will not be possible. If no buffers have been queued to the
+   * codec then this method updates the DRM session immediately without flushing the codec.
    *
    * @throws ExoPlaybackException If an error occurs updating the codec's DRM session.
+   * @return False if codec release and re-initialization was triggered due to the need to apply a
+   *     flush workaround. True in all other cases.
    */
   @TargetApi(23) // Only called when SDK_INT >= 23, but lint isn't clever enough to know.
-  private void drainAndUpdateCodecDrmSessionV23() throws ExoPlaybackException {
+  private boolean drainAndUpdateCodecDrmSessionV23() throws ExoPlaybackException {
     if (codecReceivedBuffers) {
       codecDrainState = DRAIN_STATE_SIGNAL_END_OF_STREAM;
       if (codecNeedsFlushWorkaround || codecNeedsEosFlushWorkaround) {
         codecDrainAction = DRAIN_ACTION_REINITIALIZE;
+        return false;
       } else {
         codecDrainAction = DRAIN_ACTION_FLUSH_AND_UPDATE_DRM_SESSION;
       }
@@ -1672,6 +1714,7 @@ public abstract class MediaCodecRenderer extends BaseRenderer {
       // Nothing has been queued to the decoder, so we can do the update immediately.
       updateDrmSessionV23();
     }
+    return true;
   }
 
   /**

library/core/src/main/java/com/google/android/exoplayer2/util/EventLogger.java

@@ -34,6 +34,7 @@ import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.analytics.AnalyticsListener;
 import com.google.android.exoplayer2.audio.AudioAttributes;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.source.LoadEventInfo;
 import com.google.android.exoplayer2.source.MediaLoadData;
@@ -328,7 +329,8 @@ public class EventLogger implements AnalyticsListener {
   }
 
   @Override
-  public void onAudioInputFormatChanged(EventTime eventTime, Format format) {
+  public void onAudioInputFormatChanged(
+      EventTime eventTime, Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
     logd(eventTime, "audioInputFormat", Format.toLogString(format));
   }
 
@@ -393,7 +395,8 @@ public class EventLogger implements AnalyticsListener {
   }
 
   @Override
-  public void onVideoInputFormatChanged(EventTime eventTime, Format format) {
+  public void onVideoInputFormatChanged(
+      EventTime eventTime, Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
     logd(eventTime, "videoInputFormat", Format.toLogString(format));
   }
 

library/core/src/main/java/com/google/android/exoplayer2/video/DecoderVideoRenderer.java

@@ -15,6 +15,9 @@
  */
 package com.google.android.exoplayer2.video;
 
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_DRM_SESSION_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_REUSE_NOT_IMPLEMENTED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
 import static java.lang.Math.max;
 
 import android.os.Handler;
@@ -34,6 +37,7 @@ import com.google.android.exoplayer2.decoder.Decoder;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
 import com.google.android.exoplayer2.decoder.DecoderException;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.drm.DrmSession;
 import com.google.android.exoplayer2.drm.DrmSession.DrmSessionException;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
@@ -97,9 +101,12 @@ public abstract class DecoderVideoRenderer extends BaseRenderer {
 
   private Format inputFormat;
   private Format outputFormat;
+
+  @Nullable
   private Decoder<
           VideoDecoderInputBuffer, ? extends VideoDecoderOutputBuffer, ? extends DecoderException>
       decoder;
+
   private VideoDecoderInputBuffer inputBuffer;
   private VideoDecoderOutputBuffer outputBuffer;
   @Nullable private Surface surface;
@@ -366,7 +373,24 @@ public abstract class DecoderVideoRenderer extends BaseRenderer {
 
     if (decoder == null) {
       maybeInitDecoder();
-    } else if (sourceDrmSession != decoderDrmSession || !canKeepCodec(oldFormat, inputFormat)) {
+      eventDispatcher.inputFormatChanged(inputFormat, /* decoderReuseEvaluation= */ null);
+      return;
+    }
+
+    DecoderReuseEvaluation evaluation;
+    if (sourceDrmSession != decoderDrmSession) {
+      evaluation =
+          new DecoderReuseEvaluation(
+              decoder.getName(),
+              oldFormat,
+              newFormat,
+              REUSE_RESULT_NO,
+              DISCARD_REASON_DRM_SESSION_CHANGED);
+    } else {
+      evaluation = canReuseDecoder(decoder.getName(), oldFormat, newFormat);
+    }
+
+    if (evaluation.result == REUSE_RESULT_NO) {
       if (decoderReceivedBuffers) {
         // Signal end of stream and wait for any final output buffers before re-initialization.
         decoderReinitializationState = REINITIALIZATION_STATE_SIGNAL_END_OF_STREAM;
@@ -376,8 +400,7 @@ public abstract class DecoderVideoRenderer extends BaseRenderer {
         maybeInitDecoder();
       }
     }
-
+    eventDispatcher.inputFormatChanged(inputFormat, evaluation);
-    eventDispatcher.inputFormatChanged(inputFormat);
   }
 
   /**
@@ -626,14 +649,18 @@ public abstract class DecoderVideoRenderer extends BaseRenderer {
   protected abstract void setDecoderOutputMode(@C.VideoOutputMode int outputMode);
 
   /**
-   * Returns whether the existing decoder can be kept for a new format.
+   * Evaluates whether the existing decoder can be reused for a new {@link Format}.
+   *
+   * <p>The default implementation does not allow decoder reuse.
    *
    * @param oldFormat The previous format.
    * @param newFormat The new format.
-   * @return Whether the existing decoder can be kept.
+   * @return The result of the evaluation.
    */
-  protected boolean canKeepCodec(Format oldFormat, Format newFormat) {
+  protected DecoderReuseEvaluation canReuseDecoder(
-    return false;
+      String decoderName, Format oldFormat, Format newFormat) {
+    return new DecoderReuseEvaluation(
+        decoderName, oldFormat, newFormat, REUSE_RESULT_NO, DISCARD_REASON_REUSE_NOT_IMPLEMENTED);
   }
 
   // Internal methods.

library/core/src/main/java/com/google/android/exoplayer2/video/MediaCodecVideoRenderer.java

@@ -15,7 +15,9 @@
  */
 package com.google.android.exoplayer2.video;
 
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_MAX_INPUT_SIZE_EXCEEDED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_MAX_RESOLUTION_EXCEEDED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
 import static java.lang.Math.max;
 import static java.lang.Math.min;
 
@@ -46,11 +48,12 @@ import com.google.android.exoplayer2.PlayerMessage.Target;
 import com.google.android.exoplayer2.RendererCapabilities;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DecoderDiscardReasons;
 import com.google.android.exoplayer2.drm.DrmInitData;
 import com.google.android.exoplayer2.mediacodec.MediaCodecAdapter;
 import com.google.android.exoplayer2.mediacodec.MediaCodecDecoderException;
 import com.google.android.exoplayer2.mediacodec.MediaCodecInfo;
-import com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KeepCodecResult;
 import com.google.android.exoplayer2.mediacodec.MediaCodecRenderer;
 import com.google.android.exoplayer2.mediacodec.MediaCodecSelector;
 import com.google.android.exoplayer2.mediacodec.MediaCodecUtil;
@@ -566,15 +569,24 @@ public class MediaCodecVideoRenderer extends MediaCodecRenderer {
   }
 
   @Override
-  @KeepCodecResult
+  protected DecoderReuseEvaluation canReuseCodec(
-  protected int canKeepCodec(
+      MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
-      MediaCodecAdapter codec, MediaCodecInfo codecInfo, Format oldFormat, Format newFormat) {
+    DecoderReuseEvaluation evaluation = codecInfo.canReuseCodec(oldFormat, newFormat);
-    if (newFormat.width > codecMaxValues.width
+
-        || newFormat.height > codecMaxValues.height
+    @DecoderDiscardReasons int discardReasons = evaluation.discardReasons;
-        || getMaxInputSize(codecInfo, newFormat) > codecMaxValues.inputSize) {
+    if (newFormat.width > codecMaxValues.width || newFormat.height > codecMaxValues.height) {
-      return KEEP_CODEC_RESULT_NO;
+      discardReasons |= DISCARD_REASON_VIDEO_MAX_RESOLUTION_EXCEEDED;
     }
-    return codecInfo.canKeepCodec(oldFormat, newFormat);
+    if (getMaxInputSize(codecInfo, newFormat) > codecMaxValues.inputSize) {
+      discardReasons |= DISCARD_REASON_MAX_INPUT_SIZE_EXCEEDED;
+    }
+
+    return new DecoderReuseEvaluation(
+        codecInfo.name,
+        oldFormat,
+        newFormat,
+        discardReasons != 0 ? REUSE_RESULT_NO : evaluation.result,
+        discardReasons);
   }
 
   @CallSuper
@@ -621,9 +633,12 @@ public class MediaCodecVideoRenderer extends MediaCodecRenderer {
   }
 
   @Override
-  protected void onInputFormatChanged(FormatHolder formatHolder) throws ExoPlaybackException {
+  @Nullable
-    super.onInputFormatChanged(formatHolder);
+  protected DecoderReuseEvaluation onInputFormatChanged(FormatHolder formatHolder)
-    eventDispatcher.inputFormatChanged(formatHolder.format);
+      throws ExoPlaybackException {
+    @Nullable DecoderReuseEvaluation evaluation = super.onInputFormatChanged(formatHolder);
+    eventDispatcher.inputFormatChanged(formatHolder.format, evaluation);
+    return evaluation;
   }
 
   /**
@@ -1333,7 +1348,7 @@ public class MediaCodecVideoRenderer extends MediaCodecRenderer {
         // from format to avoid codec re-use being ruled out for only this reason.
         streamFormat = streamFormat.buildUpon().setColorInfo(format.colorInfo).build();
       }
-      if (codecInfo.canKeepCodec(format, streamFormat) != KEEP_CODEC_RESULT_NO) {
+      if (codecInfo.canReuseCodec(format, streamFormat).result != REUSE_RESULT_NO) {
         haveUnknownDimensions |=
             (streamFormat.width == Format.NO_VALUE || streamFormat.height == Format.NO_VALUE);
         maxWidth = max(maxWidth, streamFormat.width);

library/core/src/main/java/com/google/android/exoplayer2/video/VideoRendererEventListener.java

@@ -25,6 +25,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.Renderer;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.util.Assertions;
 
 /**
@@ -52,12 +53,23 @@ public interface VideoRendererEventListener {
   default void onVideoDecoderInitialized(
       String decoderName, long initializedTimestampMs, long initializationDurationMs) {}
 
+  /** @deprecated Use {@link #onVideoInputFormatChanged(Format, DecoderReuseEvaluation)}. */
+  @Deprecated
+  default void onVideoInputFormatChanged(Format format) {}
+
   /**
    * Called when the format of the media being consumed by the renderer changes.
    *
    * @param format The new format.
+   * @param decoderReuseEvaluation The result of the evaluation to determine whether an existing
+   *     decoder instance can be reused for the new format, or {@code null} if the renderer did not
+   *     have a decoder.
    */
-  default void onVideoInputFormatChanged(Format format) {}
+  @SuppressWarnings("deprecation")
+  default void onVideoInputFormatChanged(
+      Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
+    onVideoInputFormatChanged(format);
+  }
 
   /**
    * Called to report the number of frames dropped by the renderer. Dropped frames are reported
@@ -172,10 +184,15 @@ public interface VideoRendererEventListener {
       }
     }
 
-    /** Invokes {@link VideoRendererEventListener#onVideoInputFormatChanged(Format)}. */
+    /**
-    public void inputFormatChanged(Format format) {
+     * Invokes {@link VideoRendererEventListener#onVideoInputFormatChanged(Format,
+     * DecoderReuseEvaluation)}.
+     */
+    public void inputFormatChanged(
+        Format format, @Nullable DecoderReuseEvaluation decoderReuseEvaluation) {
       if (handler != null) {
-        handler.post(() -> castNonNull(listener).onVideoInputFormatChanged(format));
+        handler.post(
+            () -> castNonNull(listener).onVideoInputFormatChanged(format, decoderReuseEvaluation));
       }
     }
 

library/core/src/test/java/com/google/android/exoplayer2/mediacodec/MediaCodecInfoTest.java

@@ -15,9 +15,15 @@
  */
 package com.google.android.exoplayer2.mediacodec;
 
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_AUDIO_CHANNEL_COUNT_CHANGED;
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_YES_WITH_FLUSH;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_INITIALIZATION_DATA_CHANGED;
-import static com.google.android.exoplayer2.mediacodec.MediaCodecInfo.KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_MIME_TYPE_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_RESOLUTION_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.DISCARD_REASON_VIDEO_ROTATION_CHANGED;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_NO;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITH_FLUSH;
+import static com.google.android.exoplayer2.decoder.DecoderReuseEvaluation.REUSE_RESULT_YES_WITH_RECONFIGURATION;
 import static com.google.android.exoplayer2.util.MimeTypes.AUDIO_AAC;
 import static com.google.android.exoplayer2.util.MimeTypes.VIDEO_AV1;
 import static com.google.android.exoplayer2.util.MimeTypes.VIDEO_H264;
@@ -26,6 +32,7 @@ import static com.google.common.truth.Truth.assertThat;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.video.ColorInfo;
 import com.google.common.collect.ImmutableList;
 import org.junit.Test;
@@ -71,7 +78,14 @@ public final class MediaCodecInfoTest {
     MediaCodecInfo codecInfo = buildH264CodecInfo(/* adaptive= */ true);
 
     Format hdAv1Format = FORMAT_H264_HD.buildUpon().setSampleMimeType(VIDEO_AV1).build();
-    assertThat(codecInfo.canKeepCodec(FORMAT_H264_HD, hdAv1Format)).isEqualTo(KEEP_CODEC_RESULT_NO);
+    assertThat(codecInfo.canReuseCodec(FORMAT_H264_HD, hdAv1Format))
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_H264_HD,
+                hdAv1Format,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_MIME_TYPE_CHANGED));
   }
 
   @Test
@@ -79,24 +93,42 @@ public final class MediaCodecInfoTest {
     MediaCodecInfo codecInfo = buildH264CodecInfo(/* adaptive= */ true);
 
     Format hdRotatedFormat = FORMAT_H264_HD.buildUpon().setRotationDegrees(90).build();
-    assertThat(codecInfo.canKeepCodec(FORMAT_H264_HD, hdRotatedFormat))
+    assertThat(codecInfo.canReuseCodec(FORMAT_H264_HD, hdRotatedFormat))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_H264_HD,
+                hdRotatedFormat,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_VIDEO_ROTATION_CHANGED));
   }
 
   @Test
   public void canKeepCodec_withResolutionChange_adaptiveCodec_returnsYesWithReconfiguration() {
     MediaCodecInfo codecInfo = buildH264CodecInfo(/* adaptive= */ true);
 
-    assertThat(codecInfo.canKeepCodec(FORMAT_H264_HD, FORMAT_H264_4K))
+    assertThat(codecInfo.canReuseCodec(FORMAT_H264_HD, FORMAT_H264_4K))
-        .isEqualTo(KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_H264_HD,
+                FORMAT_H264_4K,
+                REUSE_RESULT_YES_WITH_RECONFIGURATION,
+                /* discardReasons= */ 0));
   }
 
   @Test
   public void canKeepCodec_withResolutionChange_nonAdaptiveCodec_returnsNo() {
     MediaCodecInfo codecInfo = buildH264CodecInfo(/* adaptive= */ false);
 
-    assertThat(codecInfo.canKeepCodec(FORMAT_H264_HD, FORMAT_H264_4K))
+    assertThat(codecInfo.canReuseCodec(FORMAT_H264_HD, FORMAT_H264_4K))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_H264_HD,
+                FORMAT_H264_4K,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_VIDEO_RESOLUTION_CHANGED));
   }
 
   @Test
@@ -105,8 +137,14 @@ public final class MediaCodecInfoTest {
 
     Format hdVariantFormat =
         FORMAT_H264_HD.buildUpon().setInitializationData(ImmutableList.of(new byte[] {0})).build();
-    assertThat(codecInfo.canKeepCodec(FORMAT_H264_HD, hdVariantFormat))
+    assertThat(codecInfo.canReuseCodec(FORMAT_H264_HD, hdVariantFormat))
-        .isEqualTo(KEEP_CODEC_RESULT_YES_WITH_RECONFIGURATION);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_H264_HD,
+                hdVariantFormat,
+                REUSE_RESULT_YES_WITH_RECONFIGURATION,
+                /* discardReasons= */ 0));
   }
 
   @Test
@@ -115,8 +153,14 @@ public final class MediaCodecInfoTest {
 
     Format hdrVariantFormat =
         FORMAT_H264_4K.buildUpon().setColorInfo(buildColorInfo(C.COLOR_SPACE_BT601)).build();
-    assertThat(codecInfo.canKeepCodec(hdrVariantFormat, FORMAT_H264_4K))
+    assertThat(codecInfo.canReuseCodec(hdrVariantFormat, FORMAT_H264_4K))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                hdrVariantFormat,
+                FORMAT_H264_4K,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED));
   }
 
   @Test
@@ -125,8 +169,14 @@ public final class MediaCodecInfoTest {
 
     Format hdrVariantFormat =
         FORMAT_H264_4K.buildUpon().setColorInfo(buildColorInfo(C.COLOR_SPACE_BT601)).build();
-    assertThat(codecInfo.canKeepCodec(FORMAT_H264_4K, hdrVariantFormat))
+    assertThat(codecInfo.canReuseCodec(FORMAT_H264_4K, hdrVariantFormat))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_H264_4K,
+                hdrVariantFormat,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED));
   }
 
   @Test
@@ -137,18 +187,28 @@ public final class MediaCodecInfoTest {
         FORMAT_H264_4K.buildUpon().setColorInfo(buildColorInfo(C.COLOR_SPACE_BT601)).build();
     Format hdrVariantFormat2 =
         FORMAT_H264_4K.buildUpon().setColorInfo(buildColorInfo(C.COLOR_SPACE_BT709)).build();
-    assertThat(codecInfo.canKeepCodec(hdrVariantFormat1, hdrVariantFormat2))
+    assertThat(codecInfo.canReuseCodec(hdrVariantFormat1, hdrVariantFormat2))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
-    assertThat(codecInfo.canKeepCodec(hdrVariantFormat1, hdrVariantFormat2))
+            new DecoderReuseEvaluation(
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+                codecInfo.name,
+                hdrVariantFormat1,
+                hdrVariantFormat2,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_VIDEO_COLOR_INFO_CHANGED));
   }
 
   @Test
   public void canKeepCodec_audioWithDifferentChannelCounts_returnsNo() {
     MediaCodecInfo codecInfo = buildAacCodecInfo();
 
-    assertThat(codecInfo.canKeepCodec(FORMAT_AAC_STEREO, FORMAT_AAC_SURROUND))
+    assertThat(codecInfo.canReuseCodec(FORMAT_AAC_STEREO, FORMAT_AAC_SURROUND))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_AAC_STEREO,
+                FORMAT_AAC_SURROUND,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_AUDIO_CHANNEL_COUNT_CHANGED));
   }
 
   @Test
@@ -156,8 +216,14 @@ public final class MediaCodecInfoTest {
     MediaCodecInfo codecInfo = buildAacCodecInfo();
 
     Format stereoVariantFormat = FORMAT_AAC_STEREO.buildUpon().setAverageBitrate(100).build();
-    assertThat(codecInfo.canKeepCodec(FORMAT_AAC_STEREO, stereoVariantFormat))
+    assertThat(codecInfo.canReuseCodec(FORMAT_AAC_STEREO, stereoVariantFormat))
-        .isEqualTo(KEEP_CODEC_RESULT_YES_WITH_FLUSH);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_AAC_STEREO,
+                stereoVariantFormat,
+                REUSE_RESULT_YES_WITH_FLUSH,
+                /* discardReasons= */ 0));
   }
 
   @Test
@@ -169,8 +235,14 @@ public final class MediaCodecInfoTest {
             .buildUpon()
             .setInitializationData(ImmutableList.of(new byte[] {0}))
             .build();
-    assertThat(codecInfo.canKeepCodec(FORMAT_AAC_STEREO, stereoVariantFormat))
+    assertThat(codecInfo.canReuseCodec(FORMAT_AAC_STEREO, stereoVariantFormat))
-        .isEqualTo(KEEP_CODEC_RESULT_NO);
+        .isEqualTo(
+            new DecoderReuseEvaluation(
+                codecInfo.name,
+                FORMAT_AAC_STEREO,
+                stereoVariantFormat,
+                REUSE_RESULT_NO,
+                DISCARD_REASON_INITIALIZATION_DATA_CHANGED));
   }
 
   @Test

playbacktests/src/androidTest/java/com/google/android/exoplayer2/playbacktests/gts/DebugRenderersFactory.java

@@ -30,6 +30,7 @@ import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.FormatHolder;
 import com.google.android.exoplayer2.Renderer;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
+import com.google.android.exoplayer2.decoder.DecoderReuseEvaluation;
 import com.google.android.exoplayer2.mediacodec.MediaCodecAdapter;
 import com.google.android.exoplayer2.mediacodec.MediaCodecInfo;
 import com.google.android.exoplayer2.mediacodec.MediaCodecSelector;
@@ -165,12 +166,15 @@ import java.util.ArrayList;
     }
 
     @Override
-    protected void onInputFormatChanged(FormatHolder formatHolder) throws ExoPlaybackException {
+    @Nullable
-      super.onInputFormatChanged(formatHolder);
+    protected DecoderReuseEvaluation onInputFormatChanged(FormatHolder formatHolder)
+        throws ExoPlaybackException {
+      @Nullable DecoderReuseEvaluation evaluation = super.onInputFormatChanged(formatHolder);
       // Ensure timestamps of buffers queued after this format change are never inserted into the
       // queue of expected output timestamps before those of buffers that have already been queued.
       minimumInsertIndex = startIndex + queueSize;
       inputFormatChanged = true;
+      return evaluation;
     }
 
     @Override

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeAudioRenderer.java

@@ -55,7 +55,7 @@ public class FakeAudioRenderer extends FakeRenderer {
 
   @Override
   protected void onFormatChanged(Format format) {
-    eventDispatcher.inputFormatChanged(format);
+    eventDispatcher.inputFormatChanged(format, /* decoderReuseEvaluation= */ null);
     eventDispatcher.decoderInitialized(
         /* decoderName= */ "fake.audio.decoder",
         /* initializedTimestampMs= */ SystemClock.elapsedRealtime(),

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeVideoRenderer.java

@@ -85,7 +85,7 @@ public class FakeVideoRenderer extends FakeRenderer {
 
   @Override
   protected void onFormatChanged(Format format) {
-    eventDispatcher.inputFormatChanged(format);
+    eventDispatcher.inputFormatChanged(format, /* decoderReuseEvaluation= */ null);
     eventDispatcher.decoderInitialized(
         /* decoderName= */ "fake.video.decoder",
         /* initializedTimestampMs= */ SystemClock.elapsedRealtime(),