Fix Ac3 extractor sniffing for E-AC-3 frames

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213443047

library/core/src/main/java/com/google/android/exoplayer2/audio/Ac3Util.java

@@ -27,7 +27,10 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.RetentionPolicy;
 import java.nio.ByteBuffer;
 import java.nio.ByteBuffer;
 
 
-/** Utility methods for parsing Dolby TrueHD and (E-)AC3 syncframes. */
+/**
+ * Utility methods for parsing Dolby TrueHD and (E-)AC-3 syncframes. (E-)AC-3 parsing follows the
+ * definition in ETSI TS 102 366 V1.2.1.
+ */
 public final class Ac3Util {
 public final class Ac3Util {
 
 
   /** Holds sample format information as presented by a syncframe header. */
   /** Holds sample format information as presented by a syncframe header. */
@@ -237,7 +240,7 @@ public final class Ac3Util {
   public static SyncFrameInfo parseAc3SyncframeInfo(ParsableBitArray data) {
   public static SyncFrameInfo parseAc3SyncframeInfo(ParsableBitArray data) {
     int initialPosition = data.getPosition();
     int initialPosition = data.getPosition();
     data.skipBits(40);
     data.skipBits(40);
-    boolean isEac3 = data.readBits(5) == 16;
+    boolean isEac3 = data.readBits(5) == 16; // See bsid in subsection E.1.3.1.6.
     data.setPosition(initialPosition);
     data.setPosition(initialPosition);
     String mimeType;
     String mimeType;
     @StreamType int streamType = SyncFrameInfo.STREAM_TYPE_UNDEFINED;
     @StreamType int streamType = SyncFrameInfo.STREAM_TYPE_UNDEFINED;
@@ -265,7 +268,7 @@ public final class Ac3Util {
           break;
           break;
       }
       }
       data.skipBits(3); // substreamid
       data.skipBits(3); // substreamid
-      frameSize = (data.readBits(11) + 1) * 2;
+      frameSize = (data.readBits(11) + 1) * 2; // See frmsiz in subsection E.1.3.1.3.
       int fscod = data.readBits(2);
       int fscod = data.readBits(2);
       int audioBlocks;
       int audioBlocks;
       int numblkscod;
       int numblkscod;
@@ -451,19 +454,26 @@ public final class Ac3Util {
   }
   }
 
 
   /**
   /**
-   * Returns the size in bytes of the given AC-3 syncframe.
+   * Returns the size in bytes of the given (E-)AC-3 syncframe.
    *
    *
    * @param data The syncframe to parse.
    * @param data The syncframe to parse.
    * @return The syncframe size in bytes. {@link C#LENGTH_UNSET} if the input is invalid.
    * @return The syncframe size in bytes. {@link C#LENGTH_UNSET} if the input is invalid.
    */
    */
   public static int parseAc3SyncframeSize(byte[] data) {
   public static int parseAc3SyncframeSize(byte[] data) {
-    if (data.length < 5) {
+    if (data.length < 6) {
       return C.LENGTH_UNSET;
       return C.LENGTH_UNSET;
     }
     }
+    boolean isEac3 = ((data[5] & 0xFF) >> 3) == 16; // See bsid in subsection E.1.3.1.6.
+    if (isEac3) {
+      int frmsiz = (data[2] & 0x07) << 8; // Most significant 3 bits.
+      frmsiz |= data[3] & 0xFF; // Least significant 8 bits.
+      return (frmsiz + 1) * 2; // See frmsiz in subsection E.1.3.1.3.
+    } else {
       int fscod = (data[4] & 0xC0) >> 6;
       int fscod = (data[4] & 0xC0) >> 6;
       int frmsizecod = data[4] & 0x3F;
       int frmsizecod = data[4] & 0x3F;
       return getAc3SyncframeSize(fscod, frmsizecod);
       return getAc3SyncframeSize(fscod, frmsizecod);
     }
     }
+  }
 
 
   /**
   /**
    * Returns the number of audio samples in an AC-3 syncframe.
    * Returns the number of audio samples in an AC-3 syncframe.

library/core/src/main/java/com/google/android/exoplayer2/extractor/ts/Ac3Extractor.java

@@ -85,7 +85,7 @@ public final class Ac3Extractor implements Extractor {
     int headerPosition = startPosition;
     int headerPosition = startPosition;
     int validFramesCount = 0;
     int validFramesCount = 0;
     while (true) {
     while (true) {
-      input.peekFully(scratch.data, 0, 5);
+      input.peekFully(scratch.data, 0, 6);
       scratch.setPosition(0);
       scratch.setPosition(0);
       int syncBytes = scratch.readUnsignedShort();
       int syncBytes = scratch.readUnsignedShort();
       if (syncBytes != AC3_SYNC_WORD) {
       if (syncBytes != AC3_SYNC_WORD) {
@@ -103,7 +103,7 @@ public final class Ac3Extractor implements Extractor {
         if (frameSize == C.LENGTH_UNSET) {
         if (frameSize == C.LENGTH_UNSET) {
           return false;
           return false;
         }
         }
-        input.advancePeekPosition(frameSize - 5);
+        input.advancePeekPosition(frameSize - 6);
       }
       }
     }
     }
   }
   }