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Read gapless playback metadata in files with Xing metadata.

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-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=112699916
This commit is contained in:
andrewlewis 2016-01-21 10:38:04 -08:00 committed by Oliver Woodman
parent 4bea0b184f
commit 3f0244e214
3 changed files with 54 additions and 65 deletions
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14
library/src/main/java/com/google/android/exoplayer/extractor/mp3/Id3Util.java
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@ -31,13 +31,6 @@ import java.util.regex.Pattern;
*/
/* package */ final class Id3Util {
public static final class Metadata {
public int encoderDelay;
public int encoderPadding;
}
/**
* The maximum valid length for metadata in bytes.
*/
@ -54,12 +47,12 @@ import java.util.regex.Pattern;
* Peeks data from the input and parses ID3 metadata.
*
* @param input The {@link ExtractorInput} from which data should be peeked.
* @param out {@link Metadata} to populate based on the input.
* @param out {@link Mp3Extractor.Metadata} to populate based on the input.
* @return The number of bytes peeked from the input.
* @throws IOException If an error occurred peeking from the input.
* @throws InterruptedException If the thread was interrupted.
*/
public static int parseId3(ExtractorInput input, Metadata out)
public static int parseId3(ExtractorInput input, Mp3Extractor.Metadata out)
throws IOException, InterruptedException {
out.encoderDelay = 0;
out.encoderPadding = 0;
@ -100,7 +93,8 @@ import java.util.regex.Pattern;
&& !(majorVersion == 4 && (flags & 0x0F) != 0);
}
private static void parseMetadata(ParsableByteArray frame, int version, int flags, Metadata out) {
private static void parseMetadata(ParsableByteArray frame, int version, int flags,
Mp3Extractor.Metadata out) {
unescape(frame, version, flags);
// Skip any extended header.

88
library/src/main/java/com/google/android/exoplayer/extractor/mp3/Mp3Extractor.java
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@ -56,7 +56,7 @@ public final class Mp3Extractor implements Extractor {
private final long forcedFirstSampleTimestampUs;
private final ParsableByteArray scratch;
private final MpegAudioHeader synchronizedHeader;
private final Id3Util.Metadata metadata;
private final Metadata metadata;
// Extractor outputs.
private ExtractorOutput extractorOutput;
@ -86,7 +86,7 @@ public final class Mp3Extractor implements Extractor {
this.forcedFirstSampleTimestampUs = forcedFirstSampleTimestampUs;
scratch = new ParsableByteArray(4);
synchronizedHeader = new MpegAudioHeader();
metadata = new Id3Util.Metadata();
metadata = new Metadata();
basisTimeUs = -1;
}
@ -259,64 +259,51 @@ public final class Mp3Extractor implements Extractor {
* the next two frames were already peeked during synchronization.
*/
private void setupSeeker(ExtractorInput input) throws IOException, InterruptedException {
// Read the first frame which may contain a Xing or VBRI header with seeking metadata.
ParsableByteArray frame = new ParsableByteArray(synchronizedHeader.frameSize);
input.peekFully(frame.data, 0, synchronizedHeader.frameSize);
if (parseSeekerFrame(frame, input.getPosition(), input.getLength())) {
input.skipFully(synchronizedHeader.frameSize);
if (seeker != null) {
return;
}
// If there was a header but it was not usable, synchronize to the next frame so we don't use
// an invalid bitrate for CBR seeking.
input.peekFully(scratch.data, 0, 4);
scratch.setPosition(0);
MpegAudioHeader.populateHeader(scratch.readInt(), synchronizedHeader);
}
seeker = new ConstantBitrateSeeker(input.getPosition(), synchronizedHeader.bitrate * 1000,
input.getLength());
}
/**
* Tries to read seeking metadata from the given {@code frame}. If there is no seeking metadata,
* returns {@code false} and sets {@link #seeker} to null. If seeking metadata is present and
* unusable, returns {@code true} and sets {@link #seeker} to null. Otherwise, returns
* {@code true} and assigns {@link #seeker}.
*/
private boolean parseSeekerFrame(ParsableByteArray frame, long headerPosition, long inputLength) {
long position = input.getPosition();
long length = input.getLength();
// Check if there is a Xing header.
int xingBase;
if ((synchronizedHeader.version & 1) == 1) {
// MPEG 1.
if (synchronizedHeader.channels != 1) {
xingBase = 32;
} else {
xingBase = 17;
}
} else {
// MPEG 2 or 2.5.
if (synchronizedHeader.channels != 1) {
xingBase = 17;
} else {
xingBase = 9;
}
}
frame.setPosition(4 + xingBase);
int xingBase = (synchronizedHeader.version & 1) != 0
? (synchronizedHeader.channels != 1 ? 36 : 21) // MPEG 1
: (synchronizedHeader.channels != 1 ? 21 : 13); // MPEG 2 or 2.5
frame.setPosition(xingBase);
int headerData = frame.readInt();
if (headerData == XING_HEADER || headerData == INFO_HEADER) {
seeker = XingSeeker.create(synchronizedHeader, frame, headerPosition, inputLength);
return true;
seeker = XingSeeker.create(synchronizedHeader, frame, position, length);
if (seeker != null && metadata.encoderDelay == 0 && metadata.encoderPadding == 0) {
// If there is a Xing header, read gapless playback metadata at a fixed offset.
input.resetPeekPosition();
input.advancePeekPosition(xingBase + 141);
input.peekFully(scratch.data, 0, 3);
scratch.setPosition(0);
int gaplessMetadata = scratch.readUnsignedInt24();
metadata.encoderDelay = gaplessMetadata >> 12;
metadata.encoderPadding = gaplessMetadata & 0x0FFF;
}
input.skipFully(synchronizedHeader.frameSize);
} else {
// Check if there is a VBRI header.
frame.setPosition(36); // MPEG audio header (4 bytes) + 32 bytes.
headerData = frame.readInt();
if (headerData == VBRI_HEADER) {
seeker = VbriSeeker.create(synchronizedHeader, frame, headerPosition);
return true;
seeker = VbriSeeker.create(synchronizedHeader, frame, position);
input.skipFully(synchronizedHeader.frameSize);
}
}
// Neither header is present.
return false;
if (seeker == null) {
// Repopulate the synchronized header in case we had to skip an invalid seeking header, which
// would give an invalid CBR bitrate.
input.resetPeekPosition();
input.peekFully(scratch.data, 0, 4);
scratch.setPosition(0);
MpegAudioHeader.populateHeader(scratch.readInt(), synchronizedHeader);
seeker = new ConstantBitrateSeeker(input.getPosition(), synchronizedHeader.bitrate, length);
}
}
/**
@ -338,4 +325,11 @@ public final class Mp3Extractor implements Extractor {
}
/* package */ static final class Metadata {
public int encoderDelay;
public int encoderPadding;
}
}

5
library/src/main/java/com/google/android/exoplayer/util/MpegAudioHeader.java
View File

@ -172,7 +172,8 @@ public final class MpegAudioHeader {
String mimeType = MIME_TYPE_BY_LAYER[3 - layer];
int channels = ((headerData >> 6) & 3) == 3 ? 1 : 2;
header.setValues(version, mimeType, frameSize, sampleRate, channels, bitrate, samplesPerFrame);
header.setValues(version, mimeType, frameSize, sampleRate, channels, bitrate * 1000,
samplesPerFrame);
return true;
}
@ -186,7 +187,7 @@ public final class MpegAudioHeader {
public int sampleRate;
/** Number of audio channels in the frame. */
public int channels;
/** Bitrate of the frame in kbit/s. */
/** Bitrate of the frame in bit/s. */
public int bitrate;
/** Number of samples stored in the frame. */
public int samplesPerFrame;