DvbSubtitleReader.java
/*
* Copyright (C) 2017 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 androidx.media3.extractor.ts;
import static androidx.media3.extractor.ts.TsPayloadReader.FLAG_DATA_ALIGNMENT_INDICATOR;
import androidx.media3.common.C;
import androidx.media3.common.Format;
import androidx.media3.common.MimeTypes;
import androidx.media3.common.util.ParsableByteArray;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.extractor.ExtractorOutput;
import androidx.media3.extractor.TrackOutput;
import androidx.media3.extractor.ts.TsPayloadReader.DvbSubtitleInfo;
import androidx.media3.extractor.ts.TsPayloadReader.TrackIdGenerator;
import java.util.Collections;
import java.util.List;
/** Parses DVB subtitle data and extracts individual frames. */
@UnstableApi
public final class DvbSubtitleReader implements ElementaryStreamReader {
private final List<DvbSubtitleInfo> subtitleInfos;
private final TrackOutput[] outputs;
private boolean writingSample;
private int bytesToCheck;
private int sampleBytesWritten;
private long sampleTimeUs;
/**
* @param subtitleInfos Information about the DVB subtitles associated to the stream.
*/
public DvbSubtitleReader(List<DvbSubtitleInfo> subtitleInfos) {
this.subtitleInfos = subtitleInfos;
outputs = new TrackOutput[subtitleInfos.size()];
sampleTimeUs = C.TIME_UNSET;
}
@Override
public void seek() {
writingSample = false;
sampleTimeUs = C.TIME_UNSET;
}
@Override
public void createTracks(ExtractorOutput extractorOutput, TrackIdGenerator idGenerator) {
for (int i = 0; i < outputs.length; i++) {
DvbSubtitleInfo subtitleInfo = subtitleInfos.get(i);
idGenerator.generateNewId();
TrackOutput output = extractorOutput.track(idGenerator.getTrackId(), C.TRACK_TYPE_TEXT);
output.format(
new Format.Builder()
.setId(idGenerator.getFormatId())
.setSampleMimeType(MimeTypes.APPLICATION_DVBSUBS)
.setInitializationData(Collections.singletonList(subtitleInfo.initializationData))
.setLanguage(subtitleInfo.language)
.build());
outputs[i] = output;
}
}
@Override
public void packetStarted(long pesTimeUs, @TsPayloadReader.Flags int flags) {
if ((flags & FLAG_DATA_ALIGNMENT_INDICATOR) == 0) {
return;
}
writingSample = true;
if (pesTimeUs != C.TIME_UNSET) {
sampleTimeUs = pesTimeUs;
}
sampleBytesWritten = 0;
bytesToCheck = 2;
}
@Override
public void packetFinished() {
if (writingSample) {
if (sampleTimeUs != C.TIME_UNSET) {
for (TrackOutput output : outputs) {
output.sampleMetadata(sampleTimeUs, C.BUFFER_FLAG_KEY_FRAME, sampleBytesWritten, 0, null);
}
}
writingSample = false;
}
}
@Override
public void consume(ParsableByteArray data) {
if (writingSample) {
if (bytesToCheck == 2 && !checkNextByte(data, 0x20)) {
// Failed to check data_identifier
return;
}
if (bytesToCheck == 1 && !checkNextByte(data, 0x00)) {
// Check and discard the subtitle_stream_id
return;
}
int dataPosition = data.getPosition();
int bytesAvailable = data.bytesLeft();
for (TrackOutput output : outputs) {
data.setPosition(dataPosition);
output.sampleData(data, bytesAvailable);
}
sampleBytesWritten += bytesAvailable;
}
}
private boolean checkNextByte(ParsableByteArray data, int expectedValue) {
if (data.bytesLeft() == 0) {
return false;
}
if (data.readUnsignedByte() != expectedValue) {
writingSample = false;
}
bytesToCheck--;
return writingSample;
}
}