diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index f54fa79605..03148e314e 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -2,6 +2,8 @@
 
 ### dev-v2 (not yet released) ###
 
+* MP4: Support Opus and FLAC in the MP4 container, and in DASH
+  ([#4883](https://github.com/google/ExoPlayer/issues/4883)).
 * DASH: Fix detecting the end of live events
   ([#4780](https://github.com/google/ExoPlayer/issues/4780)).
 * Support seeking for a wider range of MPEG-TS streams
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/Atom.java b/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/Atom.java
index a20195139f..440e577c7d 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/Atom.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/Atom.java
@@ -145,6 +145,10 @@ import java.util.List;
   public static final int TYPE_alac = Util.getIntegerCodeForString("alac");
   public static final int TYPE_alaw = Util.getIntegerCodeForString("alaw");
   public static final int TYPE_ulaw = Util.getIntegerCodeForString("ulaw");
+  public static final int TYPE_Opus = Util.getIntegerCodeForString("Opus");
+  public static final int TYPE_dOps = Util.getIntegerCodeForString("dOps");
+  public static final int TYPE_fLaC = Util.getIntegerCodeForString("fLaC");
+  public static final int TYPE_dfLa = Util.getIntegerCodeForString("dfLa");
 
   public final int type;
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java b/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java
index 0cda3fafa8..e3d56489a6 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java
@@ -58,6 +58,9 @@ import java.util.List;
    */
   private static final int MAX_GAPLESS_TRIM_SIZE_SAMPLES = 3;
 
+  /** The magic signature for an Opus Identification header, as defined in RFC-7845. */
+  private static final byte[] opusMagic = Util.getUtf8Bytes("OpusHead");
+
   /**
    * Parses a trak atom (defined in 14496-12).
    *
@@ -679,7 +682,9 @@ import java.util.List;
           || childAtomType == Atom.TYPE__mp3
           || childAtomType == Atom.TYPE_alac
           || childAtomType == Atom.TYPE_alaw
-          || childAtomType == Atom.TYPE_ulaw) {
+          || childAtomType == Atom.TYPE_ulaw
+          || childAtomType == Atom.TYPE_Opus
+          || childAtomType == Atom.TYPE_fLaC) {
         parseAudioSampleEntry(stsd, childAtomType, childStartPosition, childAtomSize, trackId,
             language, isQuickTime, drmInitData, out, i);
       } else if (childAtomType == Atom.TYPE_TTML || childAtomType == Atom.TYPE_tx3g
@@ -976,6 +981,10 @@ import java.util.List;
       mimeType = MimeTypes.AUDIO_ALAW;
     } else if (atomType == Atom.TYPE_ulaw) {
       mimeType = MimeTypes.AUDIO_MLAW;
+    } else if (atomType == Atom.TYPE_Opus) {
+      mimeType = MimeTypes.AUDIO_OPUS;
+    } else if (atomType == Atom.TYPE_fLaC) {
+      mimeType = MimeTypes.AUDIO_FLAC;
     }
 
     byte[] initializationData = null;
@@ -1016,7 +1025,20 @@ import java.util.List;
       } else if (childAtomType == Atom.TYPE_alac) {
         initializationData = new byte[childAtomSize];
         parent.setPosition(childPosition);
-        parent.readBytes(initializationData, 0, childAtomSize);
+        parent.readBytes(initializationData, /* offset= */ 0, childAtomSize);
+      } else if (childAtomType == Atom.TYPE_dOps) {
+        // Build an Opus Identification Header (defined in RFC-7845) by concatenating the Opus Magic
+        // Signature and the body of the dOps atom.
+        int childAtomBodySize = childAtomSize - Atom.HEADER_SIZE;
+        initializationData = new byte[opusMagic.length + childAtomBodySize];
+        System.arraycopy(opusMagic, 0, initializationData, 0, opusMagic.length);
+        parent.setPosition(childPosition + Atom.HEADER_SIZE);
+        parent.readBytes(initializationData, opusMagic.length, childAtomBodySize);
+      } else if (childAtomSize == Atom.TYPE_dfLa) {
+        int childAtomBodySize = childAtomSize - Atom.FULL_HEADER_SIZE;
+        initializationData = new byte[childAtomBodySize];
+        parent.setPosition(childPosition + Atom.FULL_HEADER_SIZE);
+        parent.readBytes(initializationData, /* offset= */ 0, childAtomBodySize);
       }
       childPosition += childAtomSize;
     }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java b/library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java
index f56aac7c70..e506ae1b19 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java
@@ -207,7 +207,7 @@ public final class MimeTypes {
     if (codec == null) {
       return null;
     }
-    codec = codec.trim();
+    codec = Util.toLowerInvariant(codec.trim());
     if (codec.startsWith("avc1") || codec.startsWith("avc3")) {
       return MimeTypes.VIDEO_H264;
     } else if (codec.startsWith("hev1") || codec.startsWith("hvc1")) {
@@ -245,6 +245,8 @@ public final class MimeTypes {
       return MimeTypes.AUDIO_OPUS;
     } else if (codec.startsWith("vorbis")) {
       return MimeTypes.AUDIO_VORBIS;
+    } else if (codec.startsWith("flac")) {
+      return MimeTypes.AUDIO_FLAC;
     } else {
       return getCustomMimeTypeForCodec(codec);
     }