请同时查看我的其他问题，因为我认为它们是相关的：
问题 1
问题 2
问题 3
这是我正在使用的代码，当我按下按钮时，它会将麦克风上获得的音频信号传递到扬声器：
public class MainActivity extends Activity {
AudioManager am = null;
AudioRecord record =null;
AudioTrack track =null;
final int SAMPLE_FREQUENCY = 44100;
final int SIZE_OF_RECORD_ARRAY = 1024; // 1024 ORIGINAL
final int WAV_SAMPLE_MULTIPLICATION_FACTOR = 1;
int i= 0;
boolean isPlaying = false;
private volatile boolean keepThreadRunning;
private RandomAccessFile stateFile, stateFileTemp;
private File delFile, renFile;
String stateFileLoc = Environment.getExternalStorageDirectory().getPath();
class MyThread extends Thread{
private volatile boolean needsToPassThrough;
// /*
MyThread(){
super();
}
MyThread(boolean newPTV){
this.needsToPassThrough = newPTV;
}
// */
// /*
@Override
public void run(){
// short[] lin = new short[SIZE_OF_RECORD_ARRAY];
byte[] lin = new byte[SIZE_OF_RECORD_ARRAY];
int num = 0;
// /*
if(needsToPassThrough){
record.startRecording();
track.play();
}
// */
while (keepThreadRunning) {
// while (!isInterrupted()) {
num = record.read(lin, 0, SIZE_OF_RECORD_ARRAY);
for(i=0;i<lin.length;i++)
lin[i] *= WAV_SAMPLE_MULTIPLICATION_FACTOR;
track.write(lin, 0, num);
}
// /*
record.stop();
track.stop();
record.release();
track.release();
// */
}
// */
// /*
public void stopThread(){
keepThreadRunning = false;
}
// */
}
MyThread newThread;
private void init() {
int min = AudioRecord.getMinBufferSize(SAMPLE_FREQUENCY, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
record = new AudioRecord(MediaRecorder.AudioSource.VOICE_COMMUNICATION, SAMPLE_FREQUENCY, AudioFormat.CHANNEL_IN_MONO,
AudioFormat.ENCODING_PCM_16BIT, min);
int maxJitter = AudioTrack.getMinBufferSize(SAMPLE_FREQUENCY, AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT);
track = new AudioTrack(AudioManager.MODE_IN_COMMUNICATION, SAMPLE_FREQUENCY, AudioFormat.CHANNEL_OUT_MONO,
AudioFormat.ENCODING_PCM_16BIT, maxJitter, AudioTrack.MODE_STREAM);
am = (AudioManager) this.getSystemService(Context.AUDIO_SERVICE);
am.setMode(AudioManager.MODE_IN_COMMUNICATION);
try {
stateFile = new RandomAccessFile(stateFileLoc+"/appState.txt", "rwd");
stateFileTemp = new RandomAccessFile(stateFileLoc+"/appStateTemp.txt", "rwd");
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
delFile = new File(stateFileLoc+"/appState.txt");
renFile = new File(stateFileLoc+"/appStateTemp.txt");
}
@Override
protected void onResume(){
super.onResume();
// newThread.stopThread();
Log.d("MYLOG", "onResume() called");
init();
keepThreadRunning = true;
try {
if(stateFile.readInt() == 1){
isPlaying = true;
Log.d("MYLOG", "readInt == 1");
}
else{
isPlaying = false;
Log.d("MYLOG", "readInt <> 1");
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// */
// newThread = new MyThread(true);
newThread = new MyThread(isPlaying);
newThread.start();
}
@Override
protected void onPause(){
super.onPause();
Log.d("MYLOG", "onPause() called");
newThread.stopThread();
// android.os.Process.killProcess(android.os.Process.myPid());
try {
if(isPlaying)
stateFileTemp.writeInt(1);
else
stateFileTemp.writeInt(0);
delFile.delete();
renFile.renameTo(delFile);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setVolumeControlStream(AudioManager.MODE_IN_COMMUNICATION);
Log.d("MYLOG","onCreate() called");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
protected void onDestroy() {
super.onDestroy();
newThread.stopThread();
// android.os.Process.killProcess(android.os.Process.myPid());
// killProcess(android.os.Process.myPid());
// newThread.interrupt();
delFile.delete();
Log.d("MYLOG", "onDestroy() called");
}
public void passStop(View view){
Button playBtn = (Button) findViewById(R.id.button1);
// /*
if(!isPlaying){
record.startRecording();
track.play();
isPlaying = true;
playBtn.setText("Pause");
}
else{
record.stop();
track.pause();
isPlaying=false;
playBtn.setText("Pass through");
}
// */
}
这些文件appState.txt并被appStateTemp.txt添加以保存应用程序上次失去焦点时是否正在执行传递，但这在这里可能不是很重要。我想知道的是：
当
record.read()被调用而不调用时会发生什么record.startrecording()？有什么意义
SIZE_OF_RECORD_ARRAY？我认为它至少应该是返回的值，AudioRecord.getMinBufferSize()但在这个程序中它根本不会影响输出，即使我将它设置为 1。如果我使用 16 位 PCM 编码，我至少需要一个短变量来存储音频样本的数字等价物。然而，在这段代码中，即使我将 lin 变量从短数组更改为字节数组，输出也没有明显变化。那么 read 函数是如何将数字样本存储在数组中的呢？它会自动为每个样本分配 2 个字节的元素吗？如果是这样的话，它是小端还是大端？