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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ts;
import androidx.annotation.IntDef;
import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
import org.mozilla.thirdparty.com.google.android.exoplayer2.Format;
import org.mozilla.thirdparty.com.google.android.exoplayer2.audio.Ac3Util;
import org.mozilla.thirdparty.com.google.android.exoplayer2.audio.Ac3Util.SyncFrameInfo;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorOutput;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.TrackOutput;
import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ts.TsPayloadReader.TrackIdGenerator;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableBitArray;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
/**
* Parses a continuous (E-)AC-3 byte stream and extracts individual samples.
*/
public final class Ac3Reader implements ElementaryStreamReader {
@Documented
@Retention(RetentionPolicy.SOURCE)
@IntDef({STATE_FINDING_SYNC, STATE_READING_HEADER, STATE_READING_SAMPLE})
private @interface State {}
private static final int STATE_FINDING_SYNC = 0;
private static final int STATE_READING_HEADER = 1;
private static final int STATE_READING_SAMPLE = 2;
private static final int HEADER_SIZE = 128;
private final ParsableBitArray headerScratchBits;
private final ParsableByteArray headerScratchBytes;
private final String language;
private String trackFormatId;
private TrackOutput output;
@State private int state;
private int bytesRead;
// Used to find the header.
private boolean lastByteWas0B;
// Used when parsing the header.
private long sampleDurationUs;
private Format format;
private int sampleSize;
// Used when reading the samples.
private long timeUs;
/**
* Constructs a new reader for (E-)AC-3 elementary streams.
*/
public Ac3Reader() {
this(null);
}
/**
* Constructs a new reader for (E-)AC-3 elementary streams.
*
* @param language Track language.
*/
public Ac3Reader(String language) {
headerScratchBits = new ParsableBitArray(new byte[HEADER_SIZE]);
headerScratchBytes = new ParsableByteArray(headerScratchBits.data);
state = STATE_FINDING_SYNC;
this.language = language;
}
@Override
public void seek() {
state = STATE_FINDING_SYNC;
bytesRead = 0;
lastByteWas0B = false;
}
@Override
public void createTracks(ExtractorOutput extractorOutput, TrackIdGenerator generator) {
generator.generateNewId();
trackFormatId = generator.getFormatId();
output = extractorOutput.track(generator.getTrackId(), C.TRACK_TYPE_AUDIO);
}
@Override
public void packetStarted(long pesTimeUs, @TsPayloadReader.Flags int flags) {
timeUs = pesTimeUs;
}
@Override
public void consume(ParsableByteArray data) {
while (data.bytesLeft() > 0) {
switch (state) {
case STATE_FINDING_SYNC:
if (skipToNextSync(data)) {
state = STATE_READING_HEADER;
headerScratchBytes.data[0] = 0x0B;
headerScratchBytes.data[1] = 0x77;
bytesRead = 2;
}
break;
case STATE_READING_HEADER:
if (continueRead(data, headerScratchBytes.data, HEADER_SIZE)) {
parseHeader();
headerScratchBytes.setPosition(0);
output.sampleData(headerScratchBytes, HEADER_SIZE);
state = STATE_READING_SAMPLE;
}
break;
case STATE_READING_SAMPLE:
int bytesToRead = Math.min(data.bytesLeft(), sampleSize - bytesRead);
output.sampleData(data, bytesToRead);
bytesRead += bytesToRead;
if (bytesRead == sampleSize) {
output.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, 0, null);
timeUs += sampleDurationUs;
state = STATE_FINDING_SYNC;
}
break;
default:
break;
}
}
}
@Override
public void packetFinished() {
// Do nothing.
}
/**
* Continues a read from the provided {@code source} into a given {@code target}. It's assumed
* that the data should be written into {@code target} starting from an offset of zero.
*
* @param source The source from which to read.
* @param target The target into which data is to be read.
* @param targetLength The target length of the read.
* @return Whether the target length was reached.
*/
private boolean continueRead(ParsableByteArray source, byte[] target, int targetLength) {
int bytesToRead = Math.min(source.bytesLeft(), targetLength - bytesRead);
source.readBytes(target, bytesRead, bytesToRead);
bytesRead += bytesToRead;
return bytesRead == targetLength;
}
/**
* Locates the next syncword, advancing the position to the byte that immediately follows it. If a
* syncword was not located, the position is advanced to the limit.
*
* @param pesBuffer The buffer whose position should be advanced.
* @return Whether a syncword position was found.
*/
private boolean skipToNextSync(ParsableByteArray pesBuffer) {
while (pesBuffer.bytesLeft() > 0) {
if (!lastByteWas0B) {
lastByteWas0B = pesBuffer.readUnsignedByte() == 0x0B;
continue;
}
int secondByte = pesBuffer.readUnsignedByte();
if (secondByte == 0x77) {
lastByteWas0B = false;
return true;
} else {
lastByteWas0B = secondByte == 0x0B;
}
}
return false;
}
/**
* Parses the sample header.
*/
@SuppressWarnings("ReferenceEquality")
private void parseHeader() {
headerScratchBits.setPosition(0);
SyncFrameInfo frameInfo = Ac3Util.parseAc3SyncframeInfo(headerScratchBits);
if (format == null || frameInfo.channelCount != format.channelCount
|| frameInfo.sampleRate != format.sampleRate
|| frameInfo.mimeType != format.sampleMimeType) {
format = Format.createAudioSampleFormat(trackFormatId, frameInfo.mimeType, null,
Format.NO_VALUE, Format.NO_VALUE, frameInfo.channelCount, frameInfo.sampleRate, null,
null, 0, language);
output.format(format);
}
sampleSize = frameInfo.frameSize;
// In this class a sample is an access unit (syncframe in AC-3), but Format#sampleRate
// specifies the number of PCM audio samples per second.
sampleDurationUs = C.MICROS_PER_SECOND * frameInfo.sampleCount / format.sampleRate;
}
}
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