Updates to mp4 atom extractor/parser for dtsx support.

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

@@ -163,6 +163,9 @@ import java.util.List;
   public static final int TYPE_dtse = 0x64747365;
 
   @SuppressWarnings("ConstantCaseForConstants")
+  public static final int TYPE_dtsx = 0x64747378;
+
+  @SuppressWarnings("ConstantCaseForConstants")
   public static final int TYPE_ddts = 0x64647473;
 
   @SuppressWarnings("ConstantCaseForConstants")

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

@@ -964,6 +964,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
           || childAtomType == Atom.TYPE_dtse
           || childAtomType == Atom.TYPE_dtsh
           || childAtomType == Atom.TYPE_dtsl
+          || childAtomType == Atom.TYPE_dtsx
           || childAtomType == Atom.TYPE_samr
           || childAtomType == Atom.TYPE_sawb
           || childAtomType == Atom.TYPE_lpcm
@@ -1368,6 +1369,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
       mimeType = MimeTypes.AUDIO_DTS_HD;
     } else if (atomType == Atom.TYPE_dtse) {
       mimeType = MimeTypes.AUDIO_DTS_EXPRESS;
+    } else if (atomType == Atom.TYPE_dtsx) {
+      mimeType = MimeTypes.AUDIO_DTS_X;
     } else if (atomType == Atom.TYPE_samr) {
       mimeType = MimeTypes.AUDIO_AMR_NB;
     } else if (atomType == Atom.TYPE_sawb) {