/*
* Copyright 2016 Google Inc. All Rights Reserved.
*
* 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 pl.hypeapps.blackmirror.speechrecognition.googlespeechapi;
import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.support.annotation.NonNull;
/**
* Continuously records audio and notifies the {@link VoiceRecorder.Callback} when voice (or any
* sound) is heard.
*
* <p>The recorded audio format is always {@link AudioFormat#ENCODING_PCM_16BIT} and
* {@link AudioFormat#CHANNEL_IN_MONO}. This class will automatically pick the right sample rate
* for the device. Use {@link #getSampleRate()} to get the selected value.</p>
*/
public class VoiceRecorder {
private static final int[] SAMPLE_RATE_CANDIDATES = new int[]{16000, 11025, 22050, 44100};
private static final int CHANNEL = AudioFormat.CHANNEL_IN_MONO;
private static final int ENCODING = AudioFormat.ENCODING_PCM_16BIT;
private static final int AMPLITUDE_THRESHOLD = 100;
private static final int SPEECH_TIMEOUT_MILLIS = 2000;
private static final int MAX_SPEECH_LENGTH_MILLIS = 5 * 1000;
public static abstract class Callback {
/**
* Called when the recorder starts hearing voice.
*/
public void onVoiceStart() {
}
/**
* Called when the recorder is hearing voice.
*
* @param data The audio data in {@link AudioFormat#ENCODING_PCM_16BIT}.
* @param size The size of the actual data in {@code data}.
*/
public void onVoice(byte[] data, int size) {
}
/**
* Called when the recorder stops hearing voice.
*/
public void onVoiceEnd() {
}
}
private final Callback mCallback;
private AudioRecord mAudioRecord;
private Thread mThread;
private byte[] mBuffer;
private final Object mLock = new Object();
/** The timestamp of the last time that voice is heard. */
private long mLastVoiceHeardMillis = Long.MAX_VALUE;
/** The timestamp when the current voice is started. */
private long mVoiceStartedMillis;
public VoiceRecorder(@NonNull Callback callback) {
mCallback = callback;
}
/**
* Starts recording audio.
*
* <p>The caller is responsible for calling {@link #stop()} later.</p>
*/
public void start() {
// Stop recording if it is currently ongoing.
stop();
// Try to create a new recording session.
mAudioRecord = createAudioRecord();
if (mAudioRecord == null) {
throw new RuntimeException("Cannot instantiate VoiceRecorder");
}
// Start recording.
mAudioRecord.startRecording();
// Start processing the captured audio.
mThread = new Thread(new ProcessVoice());
mThread.start();
}
/**
* Stops recording audio.
*/
public void stop() {
synchronized (mLock) {
dismiss();
if (mThread != null) {
mThread.interrupt();
mThread = null;
}
if (mAudioRecord != null) {
mAudioRecord.stop();
mAudioRecord.release();
mAudioRecord = null;
}
mBuffer = null;
}
}
/**
* Dismisses the currently ongoing utterance.
*/
public void dismiss() {
if (mLastVoiceHeardMillis != Long.MAX_VALUE) {
mLastVoiceHeardMillis = Long.MAX_VALUE;
mCallback.onVoiceEnd();
}
}
/**
* Retrieves the sample rate currently used to record audio.
*
* @return The sample rate of recorded audio.
*/
public int getSampleRate() {
if (mAudioRecord != null) {
return mAudioRecord.getSampleRate();
}
return 0;
}
/**
* Creates a new {@link AudioRecord}.
*
* @return A newly created {@link AudioRecord}, or null if it cannot be created (missing
* permissions?).
*/
private AudioRecord createAudioRecord() {
for (int sampleRate : SAMPLE_RATE_CANDIDATES) {
final int sizeInBytes = AudioRecord.getMinBufferSize(sampleRate, CHANNEL, ENCODING);
if (sizeInBytes == AudioRecord.ERROR_BAD_VALUE) {
continue;
}
final AudioRecord audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC,
sampleRate, CHANNEL, ENCODING, sizeInBytes);
if (audioRecord.getState() == AudioRecord.STATE_INITIALIZED) {
mBuffer = new byte[sizeInBytes];
return audioRecord;
} else {
audioRecord.release();
}
}
return null;
}
/**
* Continuously processes the captured audio and notifies {@link #mCallback} of corresponding
* events.
*/
private class ProcessVoice implements Runnable {
@Override
public void run() {
while (true) {
synchronized (mLock) {
if (Thread.currentThread().isInterrupted()) {
break;
}
final int size = mAudioRecord.read(mBuffer, 0, mBuffer.length);
final long now = System.currentTimeMillis();
if (isHearingVoice(mBuffer, size)) {
if (mLastVoiceHeardMillis == Long.MAX_VALUE) {
mVoiceStartedMillis = now;
mCallback.onVoiceStart();
}
mCallback.onVoice(mBuffer, size);
mLastVoiceHeardMillis = now;
if (now - mVoiceStartedMillis > MAX_SPEECH_LENGTH_MILLIS) {
end();
}
} else if (mLastVoiceHeardMillis != Long.MAX_VALUE) {
mCallback.onVoice(mBuffer, size);
if (now - mLastVoiceHeardMillis > SPEECH_TIMEOUT_MILLIS) {
end();
}
}
}
}
}
private void end() {
mLastVoiceHeardMillis = Long.MAX_VALUE;
mCallback.onVoiceEnd();
}
private boolean isHearingVoice(byte[] buffer, int size) {
for (int i = 0; i < size - 1; i += 2) {
// The buffer has LINEAR16 in little endian.
int s = buffer[i + 1];
if (s < 0) s *= -1;
s <<= 8;
s += Math.abs(buffer[i]);
if (s > AMPLITUDE_THRESHOLD) {
return true;
}
}
return false;
}
}
}
