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Commit 110c8f6f by Oliver Woodman
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Improvements to ID3 decoder

parent 50aeb20c
Inline Side-by-side
Showing with 199 additions and 189 deletions
library/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java
......@@ -15,6 +15,7 @@
*/
package com.google.android.exoplayer2.metadata.id3;
import android.util.Log;
import com.google.android.exoplayer2.metadata.Metadata;
import com.google.android.exoplayer2.metadata.MetadataDecoder;
import com.google.android.exoplayer2.metadata.MetadataDecoderException;
......@@ -31,6 +32,8 @@ import java.util.Locale;
*/
public final class Id3Decoder implements MetadataDecoder {
private static final String TAG = "Id3Decoder";
private static final int ID3_TEXT_ENCODING_ISO_8859_1 = 0;
private static final int ID3_TEXT_ENCODING_UTF_16 = 1;
private static final int ID3_TEXT_ENCODING_UTF_16BE = 2;
......@@ -45,199 +48,185 @@ public final class Id3Decoder implements MetadataDecoder {
public Metadata decode(byte[] data, int size) throws MetadataDecoderException {
List<Id3Frame> id3Frames = new ArrayList<>();
ParsableByteArray id3Data = new ParsableByteArray(data, size);
Id3Header id3Header = decodeId3Header(id3Data);
int framesBytesLeft = id3Header.framesSize;
if (id3Header.isUnsynchronized) {
id3Data = removeUnsynchronization(id3Data, id3Header.framesSize);
framesBytesLeft = id3Data.bytesLeft();
Id3Header id3Header = decodeHeader(id3Data);
if (id3Header == null) {
return null;
}
while (framesBytesLeft > 0) {
int frameId0 = id3Data.readUnsignedByte();
int frameId1 = id3Data.readUnsignedByte();
int frameId2 = id3Data.readUnsignedByte();
int frameId3 = id3Header.majorVersion > 2 ? id3Data.readUnsignedByte() : 0;
int frameSize = id3Header.majorVersion == 2 ? id3Data.readUnsignedInt24() :
id3Header.majorVersion == 3 ? id3Data.readInt() : id3Data.readSynchSafeInt();
if (frameSize <= 1) {
break;
}
// Frame flags.
boolean isCompressed = false;
boolean isEncrypted = false;
boolean isUnsynchronized = false;
boolean hasGroupIdentifier = false;
boolean hasDataLength = false;
if (id3Header.majorVersion > 2) {
int flags = id3Data.readShort();
if (id3Header.majorVersion == 3) {
isCompressed = (flags & 0x0080) != 0;
isEncrypted = (flags & 0x0040) != 0;
hasDataLength = isCompressed;
} else {
isCompressed = (flags & 0x0008) != 0;
isEncrypted = (flags & 0x0004) != 0;
isUnsynchronized = (flags & 0x0002) != 0;
hasGroupIdentifier = (flags & 0x0040) != 0;
hasDataLength = (flags & 0x0001) != 0;
}
}
int headerSize = id3Header.majorVersion == 2 ? 6 : 10;
if (hasGroupIdentifier) {
++headerSize;
--frameSize;
id3Data.skipBytes(1);
}
if (isEncrypted) {
++headerSize;
--frameSize;
id3Data.skipBytes(1);
}
if (hasDataLength) {
headerSize += 4;
frameSize -= 4;
id3Data.skipBytes(4);
}
framesBytesLeft -= frameSize + headerSize;
int startPosition = id3Data.getPosition();
int framesSize = id3Header.framesSize;
if (id3Header.isUnsynchronized) {
framesSize = removeUnsynchronization(id3Data, id3Header.framesSize);
}
id3Data.setLimit(startPosition + framesSize);
if (isCompressed || isEncrypted) {
id3Data.skipBytes(frameSize);
} else {
try {
Id3Frame frame;
ParsableByteArray frameData = id3Data;
if (isUnsynchronized) {
frameData = removeUnsynchronization(id3Data, frameSize);
frameSize = frameData.bytesLeft();
}
if (frameId0 == 'T' && frameId1 == 'X' && frameId2 == 'X' && frameId3 == 'X') {
frame = decodeTxxxFrame(frameData, frameSize);
} else if (frameId0 == 'P' && frameId1 == 'R' && frameId2 == 'I' && frameId3 == 'V') {
frame = decodePrivFrame(frameData, frameSize);
} else if (frameId0 == 'G' && frameId1 == 'E' && frameId2 == 'O' && frameId3 == 'B') {
frame = decodeGeobFrame(frameData, frameSize);
} else if (frameId0 == 'A' && frameId1 == 'P' && frameId2 == 'I' && frameId3 == 'C') {
frame = decodeApicFrame(frameData, frameSize);
} else if (frameId0 == 'T') {
String id = frameId3 != 0 ?
String.format(Locale.US, "%c%c%c%c", frameId0, frameId1, frameId2, frameId3) :
String.format(Locale.US, "%c%c%c", frameId0, frameId1, frameId2);
frame = decodeTextInformationFrame(frameData, frameSize, id);
} else if (frameId0 == 'C' && frameId1 == 'O' && frameId2 == 'M' &&
(frameId3 == 'M' || frameId3 == 0)) {
frame = decodeCommentFrame(frameData, frameSize);
} else {
String id = frameId3 != 0 ?
String.format(Locale.US, "%c%c%c%c", frameId0, frameId1, frameId2, frameId3) :
String.format(Locale.US, "%c%c%c", frameId0, frameId1, frameId2);
frame = decodeBinaryFrame(frameData, frameSize, id);
}
id3Frames.add(frame);
} catch (UnsupportedEncodingException e) {
throw new MetadataDecoderException("Unsupported character encoding");
}
int frameHeaderSize = id3Header.majorVersion == 2 ? 6 : 10;
while (id3Data.bytesLeft() >= frameHeaderSize) {
Id3Frame frame = decodeFrame(id3Header, id3Data);
if (frame != null) {
id3Frames.add(frame);
}
}
return new Metadata(id3Frames);
}
private static int indexOfEos(byte[] data, int fromIndex, int encoding) {
int terminationPos = indexOfZeroByte(data, fromIndex);
// For single byte encoding charsets, we're done.
if (encoding == ID3_TEXT_ENCODING_ISO_8859_1 || encoding == ID3_TEXT_ENCODING_UTF_8) {
return terminationPos;
/**
* @param data A {@link ParsableByteArray} from which the header should be read.
* @return The parsed header, or null if the ID3 tag is unsupported.
* @throws MetadataDecoderException If the first three bytes differ from "ID3".
*/
private static Id3Header decodeHeader(ParsableByteArray data)
throws MetadataDecoderException {
int id1 = data.readUnsignedByte();
int id2 = data.readUnsignedByte();
int id3 = data.readUnsignedByte();
if (id1 != 'I' || id2 != 'D' || id3 != '3') {
throw new MetadataDecoderException(String.format(Locale.US,
"Unexpected ID3 tag identifier, expected \"ID3\", actual \"%c%c%c\".", id1, id2, id3));
}
// Otherwise ensure an even index and look for a second zero byte.
while (terminationPos < data.length - 1) {
if (terminationPos % 2 == 0 && data[terminationPos + 1] == (byte) 0) {
return terminationPos;
int majorVersion = data.readUnsignedByte();
data.skipBytes(1); // Skip minor version.
int flags = data.readUnsignedByte();
int framesSize = data.readSynchSafeInt();
if (majorVersion == 2) {
boolean isCompressed = (flags & 0x40) != 0;
if (isCompressed) {
Log.w(TAG, "Skipped ID3 tag with majorVersion=1 and undefined compression scheme");
return null;
}
terminationPos = indexOfZeroByte(data, terminationPos + 1);
} else if (majorVersion == 3) {
boolean hasExtendedHeader = (flags & 0x40) != 0;
if (hasExtendedHeader) {
int extendedHeaderSize = data.readInt(); // Size excluding size field.
data.skipBytes(extendedHeaderSize);
framesSize -= (extendedHeaderSize + 4);
}
} else if (majorVersion == 4) {
boolean hasExtendedHeader = (flags & 0x40) != 0;
if (hasExtendedHeader) {
int extendedHeaderSize = data.readSynchSafeInt(); // Size including size field.
data.skipBytes(extendedHeaderSize - 4);
framesSize -= extendedHeaderSize;
}
boolean hasFooter = (flags & 0x10) != 0;
if (hasFooter) {
framesSize -= 10;
}
} else {
Log.w(TAG, "Skipped ID3 tag with unsupported majorVersion=" + majorVersion);
return null;
}
return data.length;
// isUnsynchronized is advisory only in version 4. Frame level flags are used instead.
boolean isUnsynchronized = majorVersion < 4 && (flags & 0x80) != 0;
return new Id3Header(majorVersion, isUnsynchronized, framesSize);
}
private static int indexOfZeroByte(byte[] data, int fromIndex) {
for (int i = fromIndex; i < data.length; i++) {
if (data[i] == (byte) 0) {
return i;
private Id3Frame decodeFrame(Id3Header id3Header, ParsableByteArray id3Data)
throws MetadataDecoderException {
int frameId0 = id3Data.readUnsignedByte();
int frameId1 = id3Data.readUnsignedByte();
int frameId2 = id3Data.readUnsignedByte();
int frameId3 = id3Header.majorVersion >= 3 ? id3Data.readUnsignedByte() : 0;
int frameSize;
if (id3Header.majorVersion == 4) {
frameSize = id3Data.readUnsignedIntToInt();
if ((frameSize & 0x808080L) == 0) {
// Parse the frame size as a syncsafe integer, as per the spec.
frameSize = (frameSize & 0xFF) | (((frameSize >> 8) & 0xFF) << 7)
| (((frameSize >> 16) & 0xFF) << 14) | (((frameSize >> 24) & 0xFF) << 21);
} else {
// Proceed using the frame size read as an unsigned integer.
Log.w(TAG, "Frame size not specified as syncsafe integer");
}
} else if (id3Header.majorVersion == 3) {
frameSize = id3Data.readUnsignedIntToInt();
} else /* id3Header.majorVersion == 2 */ {
frameSize = id3Data.readUnsignedInt24();
}
return data.length;
}
private static int delimiterLength(int encodingByte) {
return (encodingByte == ID3_TEXT_ENCODING_ISO_8859_1 || encodingByte == ID3_TEXT_ENCODING_UTF_8)
? 1 : 2;
}
/**
* @param id3Buffer A {@link ParsableByteArray} from which data should be read.
* @return The parsed header.
* @throws MetadataDecoderException If ID3 file identifier != "ID3".
*/
private static Id3Header decodeId3Header(ParsableByteArray id3Buffer)
throws MetadataDecoderException {
int id1 = id3Buffer.readUnsignedByte();
int id2 = id3Buffer.readUnsignedByte();
int id3 = id3Buffer.readUnsignedByte();
if (id1 != 'I' || id2 != 'D' || id3 != '3') {
throw new MetadataDecoderException(String.format(Locale.US,
"Unexpected ID3 file identifier, expected \"ID3\", actual \"%c%c%c\".", id1, id2, id3));
int flags = id3Header.majorVersion >= 2 ? id3Data.readShort() : 0;
if (frameId0 == 0 && frameId1 == 0 && frameId2 == 0 && frameId3 == 0 && frameSize == 0
&& flags == 0) {
// We must be reading zero padding at the end of the tag.
id3Data.setPosition(id3Data.limit());
return null;
}
int majorVersion = id3Buffer.readUnsignedByte();
id3Buffer.skipBytes(1); // Skip minor version.
boolean isUnsynchronized = false;
int nextFramePosition = id3Data.getPosition() + frameSize;
int flags = id3Buffer.readUnsignedByte();
int framesSize = id3Buffer.readSynchSafeInt();
// Frame flags.
boolean isCompressed = false;
boolean isEncrypted = false;
boolean isUnsynchronized = false;
boolean hasDataLength = false;
boolean hasGroupIdentifier = false;
if (id3Header.majorVersion == 3) {
isCompressed = (flags & 0x0080) != 0;
isEncrypted = (flags & 0x0040) != 0;
hasGroupIdentifier = (flags & 0x0020) != 0;
hasDataLength = isCompressed;
} else if (id3Header.majorVersion == 4) {
hasGroupIdentifier = (flags & 0x0040) != 0;
isCompressed = (flags & 0x0008) != 0;
isEncrypted = (flags & 0x0004) != 0;
isUnsynchronized = (flags & 0x0002) != 0;
hasDataLength = (flags & 0x0001) != 0;
}
if (majorVersion < 4) {
// this flag is advisory in version 4, use the frame flags instead
isUnsynchronized = (flags & 0x80) != 0;
if (isCompressed || isEncrypted) {
Log.w(TAG, "Skipping unsupported compressed or encrypted frame");
id3Data.setPosition(nextFramePosition);
return null;
}
if (majorVersion == 3) {
// check for extended header
if ((flags & 0x40) != 0) {
int extendedHeaderSize = id3Buffer.readInt(); // size excluding size field
if (extendedHeaderSize == 6 || extendedHeaderSize == 10) {
id3Buffer.skipBytes(extendedHeaderSize);
framesSize -= (extendedHeaderSize + 4);
}
}
} else if (majorVersion >= 4) {
// check for extended header
if ((flags & 0x40) != 0) {
int extendedHeaderSize = id3Buffer.readSynchSafeInt(); // size including size field
if (extendedHeaderSize > 4) {
id3Buffer.skipBytes(extendedHeaderSize - 4);
}
framesSize -= extendedHeaderSize;
}
if (hasGroupIdentifier) {
frameSize--;
id3Data.skipBytes(1);
}
if (hasDataLength) {
frameSize -= 4;
id3Data.skipBytes(4);
}
if (isUnsynchronized) {
frameSize = removeUnsynchronization(id3Data, frameSize);
}
// Check if footer presents.
if ((flags & 0x10) != 0) {
framesSize -= 10;
try {
Id3Frame frame;
if (frameId0 == 'T' && frameId1 == 'X' && frameId2 == 'X' && frameId3 == 'X') {
frame = decodeTxxxFrame(id3Data, frameSize);
} else if (frameId0 == 'P' && frameId1 == 'R' && frameId2 == 'I' && frameId3 == 'V') {
frame = decodePrivFrame(id3Data, frameSize);
} else if (frameId0 == 'G' && frameId1 == 'E' && frameId2 == 'O' && frameId3 == 'B') {
frame = decodeGeobFrame(id3Data, frameSize);
} else if (frameId0 == 'A' && frameId1 == 'P' && frameId2 == 'I' && frameId3 == 'C') {
frame = decodeApicFrame(id3Data, frameSize);
} else if (frameId0 == 'T') {
String id = frameId3 != 0 ?
String.format(Locale.US, "%c%c%c%c", frameId0, frameId1, frameId2, frameId3) :
String.format(Locale.US, "%c%c%c", frameId0, frameId1, frameId2);
frame = decodeTextInformationFrame(id3Data, frameSize, id);
} else if (frameId0 == 'C' && frameId1 == 'O' && frameId2 == 'M' &&
(frameId3 == 'M' || frameId3 == 0)) {
frame = decodeCommentFrame(id3Data, frameSize);
} else {
String id = frameId3 != 0 ?
String.format(Locale.US, "%c%c%c%c", frameId0, frameId1, frameId2, frameId3) :
String.format(Locale.US, "%c%c%c", frameId0, frameId1, frameId2);
frame = decodeBinaryFrame(id3Data, frameSize, id);
}
return frame;
} catch (UnsupportedEncodingException e) {
throw new MetadataDecoderException("Unsupported character encoding");
} finally {
id3Data.setPosition(nextFramePosition);
}
return new Id3Header(majorVersion, isUnsynchronized, framesSize);
}
private static TxxxFrame decodeTxxxFrame(ParsableByteArray id3Data, int frameSize)
......@@ -368,34 +357,22 @@ public final class Id3Decoder implements MetadataDecoder {
}
/**
* Undo the unsynchronization applied to one or more frames.
* @param dataSource The original data, positioned at the beginning of a frame.
* @param count The number of valid bytes in the frames to be processed.
* @return replacement data for the frames.
* Performs in-place removal of unsynchronization for {@code length} bytes starting from
* {@link ParsableByteArray#getPosition()}
*
* @param data Contains the data to be processed.
* @param length The length of the data to be processed.
* @return The length of the data after processing.
*/
private static ParsableByteArray removeUnsynchronization(ParsableByteArray dataSource, int count) {
byte[] source = dataSource.data;
int sourceIndex = dataSource.getPosition();
int limit = sourceIndex + count;
byte[] dest = new byte[count];
int destIndex = 0;
while (sourceIndex < limit) {
byte b = source[sourceIndex++];
if ((b & 0xFF) == 0xFF) {
int nextIndex = sourceIndex+1;
if (nextIndex < limit) {
int b2 = source[nextIndex];
if (b2 == 0) {
// skip the 0 byte
++sourceIndex;
}
}
private static int removeUnsynchronization(ParsableByteArray data, int length) {
byte[] bytes = data.data;
for (int i = data.getPosition(); i + 1 < length; i++) {
if ((bytes[i] & 0xFF) == 0xFF && bytes[i + 1] == 0x00) {
System.arraycopy(bytes, i + 2, bytes, i + 1, length - i - 2);
length--;
}
dest[destIndex++] = b;
}
return new ParsableByteArray(dest, destIndex);
return length;
}
/**
......@@ -418,6 +395,39 @@ public final class Id3Decoder implements MetadataDecoder {
}
}
private static int indexOfEos(byte[] data, int fromIndex, int encoding) {
int terminationPos = indexOfZeroByte(data, fromIndex);
// For single byte encoding charsets, we're done.
if (encoding == ID3_TEXT_ENCODING_ISO_8859_1 || encoding == ID3_TEXT_ENCODING_UTF_8) {
return terminationPos;
}
// Otherwise ensure an even index and look for a second zero byte.
while (terminationPos < data.length - 1) {
if (terminationPos % 2 == 0 && data[terminationPos + 1] == (byte) 0) {
return terminationPos;
}
terminationPos = indexOfZeroByte(data, terminationPos + 1);
}
return data.length;
}
private static int indexOfZeroByte(byte[] data, int fromIndex) {
for (int i = fromIndex; i < data.length; i++) {
if (data[i] == (byte) 0) {
return i;
}
}
return data.length;
}
private static int delimiterLength(int encodingByte) {
return (encodingByte == ID3_TEXT_ENCODING_ISO_8859_1 || encodingByte == ID3_TEXT_ENCODING_UTF_8)
? 1 : 2;
}
public static String decodeGenre(int code) {
return (0 < code && code <= standardGenres.length) ? standardGenres[code - 1] : null;
}
......
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