Add support for 'mett' sample description

PiperOrigin-RevId: 333272292

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/Atom.java

@@ -356,6 +356,9 @@ import java.util.List;
   public static final int TYPE_camm = 0x63616d6d;
   public static final int TYPE_camm = 0x63616d6d;
 
 
   @SuppressWarnings("ConstantCaseForConstants")
   @SuppressWarnings("ConstantCaseForConstants")
+  public static final int TYPE_mett = 0x6d657474;
+
+  @SuppressWarnings("ConstantCaseForConstants")
   public static final int TYPE_alac = 0x616c6163;
   public static final int TYPE_alac = 0x616c6163;
 
 
   @SuppressWarnings("ConstantCaseForConstants")
   @SuppressWarnings("ConstantCaseForConstants")

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java

@@ -891,6 +891,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
           || childAtomType == Atom.TYPE_c608) {
           || childAtomType == Atom.TYPE_c608) {
         parseTextSampleEntry(stsd, childAtomType, childStartPosition, childAtomSize, trackId,
         parseTextSampleEntry(stsd, childAtomType, childStartPosition, childAtomSize, trackId,
             language, out);
             language, out);
+      } else if (childAtomType == Atom.TYPE_mett) {
+        parseMetaDataSampleEntry(stsd, childAtomType, childStartPosition, trackId, out);
       } else if (childAtomType == Atom.TYPE_camm) {
       } else if (childAtomType == Atom.TYPE_camm) {
         out.format =
         out.format =
             new Format.Builder()
             new Format.Builder()
@@ -1097,6 +1099,18 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
             .build();
             .build();
   }
   }
 
 
+  private static void parseMetaDataSampleEntry(
+      ParsableByteArray parent, int atomType, int position, int trackId, StsdData out) {
+    parent.setPosition(position + Atom.HEADER_SIZE + StsdData.STSD_HEADER_SIZE);
+    if (atomType == Atom.TYPE_mett) {
+      parent.readNullTerminatedString(); // Skip optional content_encoding
+      @Nullable String mimeType = parent.readNullTerminatedString();
+      if (mimeType != null) {
+        out.format = new Format.Builder().setId(trackId).setSampleMimeType(mimeType).build();
+      }
+    }
+  }
+
   /**
   /**
    * Parses the edts atom (defined in ISO/IEC 14496-12 subsection 8.6.5).
    * Parses the edts atom (defined in ISO/IEC 14496-12 subsection 8.6.5).
    *
    *