Parse encoder delay and padding from ID3 metadata in MP3.

Based on AOSP's MP3Extractor.cpp and ID3.cpp.

Issue: #497
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112685664

library/src/androidTest/java/com/google/android/exoplayer/util/ParsableByteArrayTest.java

@@ -18,6 +18,7 @@ package com.google.android.exoplayer.util;
 import junit.framework.TestCase;
 import junit.framework.TestCase;
 
 
 import java.nio.ByteBuffer;
 import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
 import java.util.Arrays;
 import java.util.Arrays;
 
 
 /**
 /**
@@ -415,4 +416,11 @@ public class ParsableByteArrayTest extends TestCase {
     assertNull(parser.readLine());
     assertNull(parser.readLine());
   }
   }
 
 
+  public void testReadString() {
+    byte[] bytes = new byte[] {'t', 'e', 's', 't'};
+    ParsableByteArray testArray = new ParsableByteArray(bytes);
+    assertEquals("test", testArray.readString(bytes.length, Charset.forName("UTF-8")));
+    assertEquals(bytes.length, testArray.getPosition());
+  }
+
 }
 }

library/src/main/java/com/google/android/exoplayer/extractor/mp3/Mp3Extractor.java

@@ -49,7 +49,6 @@ public final class Mp3Extractor implements Extractor {
    * Mask that includes the audio header values that must match between frames.
    * Mask that includes the audio header values that must match between frames.
    */
    */
   private static final int HEADER_MASK = 0xFFFE0C00;
   private static final int HEADER_MASK = 0xFFFE0C00;
-  private static final int ID3_TAG = Util.getIntegerCodeForString("ID3");
   private static final int XING_HEADER = Util.getIntegerCodeForString("Xing");
   private static final int XING_HEADER = Util.getIntegerCodeForString("Xing");
   private static final int INFO_HEADER = Util.getIntegerCodeForString("Info");
   private static final int INFO_HEADER = Util.getIntegerCodeForString("Info");
   private static final int VBRI_HEADER = Util.getIntegerCodeForString("VBRI");
   private static final int VBRI_HEADER = Util.getIntegerCodeForString("VBRI");
@@ -57,6 +56,7 @@ public final class Mp3Extractor implements Extractor {
   private final long forcedFirstSampleTimestampUs;
   private final long forcedFirstSampleTimestampUs;
   private final ParsableByteArray scratch;
   private final ParsableByteArray scratch;
   private final MpegAudioHeader synchronizedHeader;
   private final MpegAudioHeader synchronizedHeader;
+  private final Id3Util.Metadata metadata;
 
 
   // Extractor outputs.
   // Extractor outputs.
   private ExtractorOutput extractorOutput;
   private ExtractorOutput extractorOutput;
@@ -86,6 +86,7 @@ public final class Mp3Extractor implements Extractor {
     this.forcedFirstSampleTimestampUs = forcedFirstSampleTimestampUs;
     this.forcedFirstSampleTimestampUs = forcedFirstSampleTimestampUs;
     scratch = new ParsableByteArray(4);
     scratch = new ParsableByteArray(4);
     synchronizedHeader = new MpegAudioHeader();
     synchronizedHeader = new MpegAudioHeader();
+    metadata = new Id3Util.Metadata();
     basisTimeUs = -1;
     basisTimeUs = -1;
   }
   }
 
 
@@ -194,30 +195,10 @@ public final class Mp3Extractor implements Extractor {
   private boolean synchronize(ExtractorInput input, boolean sniffing)
   private boolean synchronize(ExtractorInput input, boolean sniffing)
       throws IOException, InterruptedException {
       throws IOException, InterruptedException {
     input.resetPeekPosition();
     input.resetPeekPosition();
-    int peekedId3Bytes = 0;
-    if (input.getPosition() == 0) {
-      // Skip any ID3 headers at the start of the file.
-      while (true) {
-        input.peekFully(scratch.data, 0, 3);
-        scratch.setPosition(0);
-        if (scratch.readUnsignedInt24() != ID3_TAG) {
-          break;
-        }
-        input.advancePeekPosition(2 + 1); // version, flags
-        input.peekFully(scratch.data, 0, 4);
-        scratch.setPosition(0);
-        int headerLength = scratch.readSynchSafeInt();
-        input.advancePeekPosition(headerLength);
-        peekedId3Bytes += 10 + headerLength;
-      }
-      input.resetPeekPosition();
-      input.advancePeekPosition(peekedId3Bytes);
-    }
-
-    // For sniffing, limit the search range to the length of an audio frame after any ID3 metadata.
     int searched = 0;
     int searched = 0;
     int validFrameCount = 0;
     int validFrameCount = 0;
     int candidateSynchronizedHeaderData = 0;
     int candidateSynchronizedHeaderData = 0;
+    int peekedId3Bytes = input.getPosition() == 0 ? Id3Util.parseId3(input, metadata) : 0;
     while (true) {
     while (true) {
       if (sniffing && searched == MAX_SNIFF_BYTES) {
       if (sniffing && searched == MAX_SNIFF_BYTES) {
         return false;
         return false;

library/src/main/java/com/google/android/exoplayer/util/ParsableByteArray.java

@@ -16,6 +16,7 @@
 package com.google.android.exoplayer.util;
 package com.google.android.exoplayer.util;
 
 
 import java.nio.ByteBuffer;
 import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
 
 
 /**
 /**
  * Wraps a byte array, providing a set of methods for parsing data from it. Numerical values are
  * Wraps a byte array, providing a set of methods for parsing data from it. Numerical values are
@@ -358,4 +359,17 @@ public final class ParsableByteArray {
     return line;
     return line;
   }
   }
 
 
+  /**
+   * Reads the next {@code bytes} bytes as characters in the specified {@link Charset}.
+   *
+   * @param bytes The number of bytes to read.
+   * @param charset The character set of the encoded characters.
+   * @return The string encoded by the bytes in the specified character set.
+   */
+  public String readString(int bytes, Charset charset) {
+    String result = new String(data, position, bytes, charset);
+    position += bytes;
+    return result;
+  }
+
 }
 }