SilentAudioGenerator.java
/*
* Copyright 2022 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.transformer;
import androidx.media3.common.C;
import androidx.media3.common.audio.AudioProcessor.AudioFormat;
import androidx.media3.common.util.Util;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.concurrent.atomic.AtomicLong;
/* package */ final class SilentAudioGenerator {
private static final int DEFAULT_BUFFER_SIZE_FRAMES = 1024;
private final int sampleRate;
private final int frameSize;
private final ByteBuffer internalBuffer;
private final AtomicLong remainingBytesToOutput;
public SilentAudioGenerator(AudioFormat format) {
sampleRate = format.sampleRate;
frameSize = Util.getPcmFrameSize(format.encoding, format.channelCount);
internalBuffer =
ByteBuffer.allocateDirect(DEFAULT_BUFFER_SIZE_FRAMES * frameSize)
.order(ByteOrder.nativeOrder());
internalBuffer.flip();
remainingBytesToOutput = new AtomicLong();
}
/**
* Adds a silence duration to generate.
*
* <p>Can be called from any thread.
*
* @param durationUs The duration of the additional silence to generate, in microseconds.
*/
public void addSilence(long durationUs) {
long outputFrameCount = (sampleRate * durationUs) / C.MICROS_PER_SECOND;
remainingBytesToOutput.addAndGet(frameSize * outputFrameCount);
}
public ByteBuffer getBuffer() {
long remainingBytesToOutput = this.remainingBytesToOutput.get();
if (!internalBuffer.hasRemaining()) {
// "next" buffer.
internalBuffer.clear();
if (remainingBytesToOutput < internalBuffer.capacity()) {
internalBuffer.limit((int) remainingBytesToOutput);
}
// Only reduce remaining bytes when we "generate" a new one.
this.remainingBytesToOutput.addAndGet(-internalBuffer.remaining());
}
return internalBuffer;
}
public boolean hasRemaining() {
return internalBuffer.hasRemaining() || remainingBytesToOutput.get() > 0;
}
}