Add support for mp2 boxes.

Issue: #7967
PiperOrigin-RevId: 333709003

RELEASENOTES.md

@@ -19,6 +19,9 @@
     *   Add support for `\h` SSA/ASS style override code (non-breaking space).
 *   Audio:
     *   Retry playback after some types of `AudioTrack` error.
+*   Extractors:
+    *   Add support for .mp2 boxes in the `AtomParsers`
+        ([#7967](https://github.com/google/ExoPlayer/issues/7967)).
 
 ### 2.12.0 (2020-09-11) ###
 

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

@@ -116,6 +116,9 @@ import java.util.List;
   public static final int TYPE_mp4a = 0x6d703461;
 
   @SuppressWarnings("ConstantCaseForConstants")
+  public static final int TYPE__mp2 = 0x2e6d7032;
+
+  @SuppressWarnings("ConstantCaseForConstants")
   public static final int TYPE__mp3 = 0x2e6d7033;
 
   @SuppressWarnings("ConstantCaseForConstants")

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

@@ -878,6 +878,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
           || childAtomType == Atom.TYPE_lpcm
           || childAtomType == Atom.TYPE_sowt
           || childAtomType == Atom.TYPE_twos
+          || childAtomType == Atom.TYPE__mp2
           || childAtomType == Atom.TYPE__mp3
           || childAtomType == Atom.TYPE_alac
           || childAtomType == Atom.TYPE_alaw
@@ -1243,7 +1244,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
     } else if (atomType == Atom.TYPE_twos) {
       mimeType = MimeTypes.AUDIO_RAW;
       pcmEncoding = C.ENCODING_PCM_16BIT_BIG_ENDIAN;
-    } else if (atomType == Atom.TYPE__mp3) {
+    } else if (atomType == Atom.TYPE__mp2 || atomType == Atom.TYPE__mp3) {
       mimeType = MimeTypes.AUDIO_MPEG;
     } else if (atomType == Atom.TYPE_alac) {
       mimeType = MimeTypes.AUDIO_ALAC;