Add support for MP4/QuickTime non-full meta atoms

PiperOrigin-RevId: 357160215

RELEASENOTES.md

 # Release notes
 
+### dev-v2 ###
+
+*   Extractors:
+    *   Add support for MP4 and QuickTime meta atoms that are not full atoms.
+
 ### 2.13.1 (2021-02-12)
 
 *   Live streaming:

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

@@ -145,12 +145,11 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
    * Parses a udta atom.
    *
    * @param udtaAtom The udta (user data) atom to decode.
-   * @param isQuickTime True for QuickTime media. False otherwise.
    * @return A {@link Pair} containing the metadata from the meta child atom as first value (if
    *     any), and the metadata from the smta child atom as second value (if any).
    */
   public static Pair<@NullableType Metadata, @NullableType Metadata> parseUdta(
-      Atom.LeafAtom udtaAtom, boolean isQuickTime) {
+      Atom.LeafAtom udtaAtom) {
     ParsableByteArray udtaData = udtaAtom.data;
     udtaData.setPosition(Atom.HEADER_SIZE);
     @Nullable Metadata metaMetadata = null;
@@ -159,8 +158,7 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
       int atomPosition = udtaData.getPosition();
       int atomSize = udtaData.readInt();
       int atomType = udtaData.readInt();
-      // Meta boxes are regular boxes rather than full boxes in QuickTime. Ignore them for now.
-      if (atomType == Atom.TYPE_meta && !isQuickTime) {
+      if (atomType == Atom.TYPE_meta) {
         udtaData.setPosition(atomPosition);
         metaMetadata = parseUdtaMeta(udtaData, atomPosition + atomSize);
       } else if (atomType == Atom.TYPE_smta) {
@@ -227,6 +225,28 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
     return entries.isEmpty() ? null : new Metadata(entries);
   }
 
+  /**
+   * Possibly skips the version and flags fields (1+3 byte) of a full meta atom.
+   *
+   * <p>Atoms of type {@link Atom#TYPE_meta} are defined to be full atoms which have four additional
+   * bytes for a version and a flags field (see 4.2 'Object Structure' in ISO/IEC 14496-12:2005).
+   * QuickTime do not have such a full box structure. Since some of these files are encoded wrongly,
+   * we can't rely on the file type though. Instead we must check the 4 bytes after the common
+   * header bytes ourselves.
+   *
+   * @param meta The 4 or more bytes following the meta atom size and type.
+   */
+  public static void maybeSkipRemainingMetaAtomHeaderBytes(ParsableByteArray meta) {
+    int startPosition = meta.getPosition();
+    // The next 4 bytes can be either:
+    // (iso) 4 zero bytes (version + flags)
+    // (qt)  4 byte size of next atom
+    // In case of (iso) we need to skip the next 4 bytes.
+    if (meta.readInt() != 0) {
+      meta.setPosition(startPosition);
+    }
+  }
+
   /**
    * Parses a trak atom (defined in ISO/IEC 14496-12).
    *
@@ -677,7 +697,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
 
   @Nullable
   private static Metadata parseUdtaMeta(ParsableByteArray meta, int limit) {
-    meta.skipBytes(Atom.FULL_HEADER_SIZE);
+    meta.skipBytes(Atom.HEADER_SIZE);
+    maybeSkipRemainingMetaAtomHeaderBytes(meta);
     while (meta.getPosition() < limit) {
       int atomPosition = meta.getPosition();
       int atomSize = meta.readInt();

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/Mp4Extractor.java

@@ -470,7 +470,7 @@ public final class Mp4Extractor implements Extractor, SeekMap {
     @Nullable Atom.LeafAtom udta = moov.getLeafAtomOfType(Atom.TYPE_udta);
     if (udta != null) {
       Pair<@NullableType Metadata, @NullableType Metadata> udtaMetadata =
-          AtomParsers.parseUdta(udta, isQuickTime);
+          AtomParsers.parseUdta(udta);
       udtaMetaMetadata = udtaMetadata.first;
       smtaMetadata = udtaMetadata.second;
       if (udtaMetaMetadata != null) {
@@ -727,29 +727,12 @@ public final class Mp4Extractor implements Extractor, SeekMap {
     }
   }
 
-  /**
-   * Possibly skips the version and flags fields (1+3 byte) of a full meta atom of the {@code
-   * input}.
-   *
-   * <p>Atoms of type {@link Atom#TYPE_meta} are defined to be full atoms which have four additional
-   * bytes for a version and a flags field (see 4.2 'Object Structure' in ISO/IEC 14496-12:2005).
-   * QuickTime do not have such a full box structure. Since some of these files are encoded wrongly,
-   * we can't rely on the file type though. Instead we must check the 8 bytes after the common
-   * header bytes ourselves.
-   */
   private void maybeSkipRemainingMetaAtomHeaderBytes(ExtractorInput input) throws IOException {
-    scratch.reset(8);
-    // Peek the next 8 bytes which can be either
-    // (iso) [1 byte version + 3 bytes flags][4 byte size of next atom]
-    // (qt)  [4 byte size of next atom      ][4 byte hdlr atom type   ]
-    // In case of (iso) we need to skip the next 4 bytes.
-    input.peekFully(scratch.getData(), 0, 8);
-    scratch.skipBytes(4);
-    if (scratch.readInt() == Atom.TYPE_hdlr) {
-      input.resetPeekPosition();
-    } else {
-      input.skipFully(4);
-    }
+    scratch.reset(4);
+    input.peekFully(scratch.getData(), 0, 4);
+    AtomParsers.maybeSkipRemainingMetaAtomHeaderBytes(scratch);
+    input.skipFully(scratch.getPosition());
+    input.resetPeekPosition();
   }
 
   /** Processes an atom whose payload does not need to be parsed. */