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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.text.cea;
import androidx.annotation.NonNull;
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.text.Subtitle;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.SubtitleDecoder;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.SubtitleDecoderException;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.SubtitleInputBuffer;
import org.mozilla.thirdparty.com.google.android.exoplayer2.text.SubtitleOutputBuffer;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Assertions;
import java.util.ArrayDeque;
import java.util.PriorityQueue;
/**
* Base class for subtitle parsers for CEA captions.
*/
/* package */ abstract class CeaDecoder implements SubtitleDecoder {
private static final int NUM_INPUT_BUFFERS = 10;
private static final int NUM_OUTPUT_BUFFERS = 2;
private final ArrayDeque<CeaInputBuffer> availableInputBuffers;
private final ArrayDeque<SubtitleOutputBuffer> availableOutputBuffers;
private final PriorityQueue<CeaInputBuffer> queuedInputBuffers;
private CeaInputBuffer dequeuedInputBuffer;
private long playbackPositionUs;
private long queuedInputBufferCount;
public CeaDecoder() {
availableInputBuffers = new ArrayDeque<>();
for (int i = 0; i < NUM_INPUT_BUFFERS; i++) {
availableInputBuffers.add(new CeaInputBuffer());
}
availableOutputBuffers = new ArrayDeque<>();
for (int i = 0; i < NUM_OUTPUT_BUFFERS; i++) {
availableOutputBuffers.add(new CeaOutputBuffer());
}
queuedInputBuffers = new PriorityQueue<>();
}
@Override
public abstract String getName();
@Override
public void setPositionUs(long positionUs) {
playbackPositionUs = positionUs;
}
@Override
public SubtitleInputBuffer dequeueInputBuffer() throws SubtitleDecoderException {
Assertions.checkState(dequeuedInputBuffer == null);
if (availableInputBuffers.isEmpty()) {
return null;
}
dequeuedInputBuffer = availableInputBuffers.pollFirst();
return dequeuedInputBuffer;
}
@Override
public void queueInputBuffer(SubtitleInputBuffer inputBuffer) throws SubtitleDecoderException {
Assertions.checkArgument(inputBuffer == dequeuedInputBuffer);
if (inputBuffer.isDecodeOnly()) {
// We can drop this buffer early (i.e. before it would be decoded) as the CEA formats allow
// for decoding to begin mid-stream.
releaseInputBuffer(dequeuedInputBuffer);
} else {
dequeuedInputBuffer.queuedInputBufferCount = queuedInputBufferCount++;
queuedInputBuffers.add(dequeuedInputBuffer);
}
dequeuedInputBuffer = null;
}
@Override
public SubtitleOutputBuffer dequeueOutputBuffer() throws SubtitleDecoderException {
if (availableOutputBuffers.isEmpty()) {
return null;
}
// iterate through all available input buffers whose timestamps are less than or equal
// to the current playback position; processing input buffers for future content should
// be deferred until they would be applicable
while (!queuedInputBuffers.isEmpty()
&& queuedInputBuffers.peek().timeUs <= playbackPositionUs) {
CeaInputBuffer inputBuffer = queuedInputBuffers.poll();
// If the input buffer indicates we've reached the end of the stream, we can
// return immediately with an output buffer propagating that
if (inputBuffer.isEndOfStream()) {
SubtitleOutputBuffer outputBuffer = availableOutputBuffers.pollFirst();
outputBuffer.addFlag(C.BUFFER_FLAG_END_OF_STREAM);
releaseInputBuffer(inputBuffer);
return outputBuffer;
}
decode(inputBuffer);
// check if we have any caption updates to report
if (isNewSubtitleDataAvailable()) {
// Even if the subtitle is decode-only; we need to generate it to consume the data so it
// isn't accidentally prepended to the next subtitle
Subtitle subtitle = createSubtitle();
if (!inputBuffer.isDecodeOnly()) {
SubtitleOutputBuffer outputBuffer = availableOutputBuffers.pollFirst();
outputBuffer.setContent(inputBuffer.timeUs, subtitle, Format.OFFSET_SAMPLE_RELATIVE);
releaseInputBuffer(inputBuffer);
return outputBuffer;
}
}
releaseInputBuffer(inputBuffer);
}
return null;
}
private void releaseInputBuffer(CeaInputBuffer inputBuffer) {
inputBuffer.clear();
availableInputBuffers.add(inputBuffer);
}
protected void releaseOutputBuffer(SubtitleOutputBuffer outputBuffer) {
outputBuffer.clear();
availableOutputBuffers.add(outputBuffer);
}
@Override
public void flush() {
queuedInputBufferCount = 0;
playbackPositionUs = 0;
while (!queuedInputBuffers.isEmpty()) {
releaseInputBuffer(queuedInputBuffers.poll());
}
if (dequeuedInputBuffer != null) {
releaseInputBuffer(dequeuedInputBuffer);
dequeuedInputBuffer = null;
}
}
@Override
public void release() {
// Do nothing
}
/**
* Returns whether there is data available to create a new {@link Subtitle}.
*/
protected abstract boolean isNewSubtitleDataAvailable();
/**
* Creates a {@link Subtitle} from the available data.
*/
protected abstract Subtitle createSubtitle();
/**
* Filters and processes the raw data, providing {@link Subtitle}s via {@link #createSubtitle()}
* when sufficient data has been processed.
*/
protected abstract void decode(SubtitleInputBuffer inputBuffer);
private static final class CeaInputBuffer extends SubtitleInputBuffer
implements Comparable<CeaInputBuffer> {
private long queuedInputBufferCount;
@Override
public int compareTo(@NonNull CeaInputBuffer other) {
if (isEndOfStream() != other.isEndOfStream()) {
return isEndOfStream() ? 1 : -1;
}
long delta = timeUs - other.timeUs;
if (delta == 0) {
delta = queuedInputBufferCount - other.queuedInputBufferCount;
if (delta == 0) {
return 0;
}
}
return delta > 0 ? 1 : -1;
}
}
private final class CeaOutputBuffer extends SubtitleOutputBuffer {
@Override
public final void release() {
releaseOutputBuffer(this);
}
}
}
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