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我试图通过音频插孔近乎实时地检测出方波信号(麦克风)。出于这个原因,我在流模式下使用AudioRecord类。但我的问题是,我的手机(麦克风)总是工作不同。有时我使用20,000的阈值,有时我必须将阈值调整为1'000以检测(第一个脉冲的)边缘。信号的电压范围是0到3V。我不确定我的麦克风是否工作不正常,或者adc是否使用不同的参考电压?Android - AudioRecord:通过音频插孔(麦克风)检测脉宽调制信号
我还没有任何想法如何解决这个问题。 我真的希望你能帮助我。
这里我的源代码:
公共类ReceiveCom扩展的AsyncTask实现对MIC层{
private AudioRecord audioRecord;
private int sampleRate = 44100;
private short[] audioData;
private int sizeInShorts;
private boolean isRunning=false;
private int receiveBuffer;
private int minBuffersize;
private boolean ready=false;
private int audioResult,dataCounter=0;
private short[] dataBits = new short[8];
@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
public ReceiveCom(){
try{
minBuffersize = AudioRecord.getMinBufferSize(sampleRate, AudioFormat.CHANNEL_IN_MONO,
AudioFormat.ENCODING_PCM_16BIT);
audioRecord = new AudioRecord(AudioSource.MIC, sampleRate, AudioFormat.CHANNEL_IN_MONO,
AudioFormat.ENCODING_PCM_16BIT, minBuffersize);
if (audioRecord.getState() != AudioRecord.STATE_INITIALIZED){
throw new Exception("AudioRecord init failed");
}
audioData = new short[2*minBuffersize];
Log.e("ERROR", "ReceiveCom constructor: OK ");
}
catch(IllegalArgumentException e){
Log.e("ERROR", "IllegalArgumentException: " + e);
}
catch(Exception e){
Log.e("ERROR", "ConstructorException: " + e);
}
finally{
Log.e("ERROR", "ReceiveCom constructor: END ");
}
if(Build.VERSION.SDK_INT >= 17){
if(AutomaticGainControl.isAvailable()){
Log.e("INFO", "AGC is available");
//AutomaticGainControl.create(audioRecord.getAudioSessionId());
}
}
}
protected Void doInBackground(Void... arg0) {
audioRecord.setPositionNotificationPeriod(minBuffersize);
audioRecord.setRecordPositionUpdateListener(new OnRecordPositionUpdateListener(){
@Override
public void onPeriodicNotification(AudioRecord myRecorder) {
int timeCounter=0,bitCounter=0,i=0;
boolean edgeTriggered=false, bitReady=false;
int dB,edgeThreshold=10000,idleThreshold=edgeThreshold/5;
for(i=2; i<audioResult; i=i+1){
if(edgeTriggered==false && audioData[i-2]<=idleThreshold && audioData[i-1]>=edgeThreshold && audioData[i]>=edgeThreshold){
Log.e("DEBUG","audioData["+i+"]: "+audioData[i]);
timeCounter++;
edgeTriggered=true;
bitReady=false;
}
}
}
@Override
public void onMarkerReached(AudioRecord recorder) { }
});
audioRecord.startRecording();
while(isRunning){
audioResult = audioRecord.read(audioData, 0, minBuffersize);
}
audioRecord.stop();
audioRecord.release();
return null;
}
您不应该期望音频通道通过信号的DC分量,但输入上出现的任何恒定偏移电压可能会短暂出现然后衰减。可能你需要为你的解码器建立幅度和偏移的跟踪方案。 – 2014-01-30 16:48:16