我正在使用其AudioRecord和AudioTrack类制作Android-to-Android VoIP(扬声器)应用程序,以及通过NDK的Speex进行回声消除.我能够成功传入并从Speex的speex_echo_cancellation()函数中检索数据,但回声仍然存在.

这是记录/发送和接收/播放音频的相关android线程代码：

//constructor

public MyThread(DatagramSocket socket, int frameSize, int filterLength){

this.socket = socket;

nativeMethod_initEchoState(frameSize, filterLength);

}

public void run(){

short[] audioShorts, recvShorts, recordedShorts, filteredShorts;

byte[] audioBytes, recvBytes;

int shortsRead;

DatagramPacket packet;

//initialize recorder and player

int samplingRate = 8000;

int managerBufferSize = 2000;

AudioTrack player = new AudioTrack(AudioManager.STREAM_MUSIC, samplingRate, AudioFormat.CHANNEL_OUT_MONO, AudioFormat.ENCODING_PCM_16BIT, managerBufferSize, AudioTrack.MODE_STREAM);

recorder = new AudioRecord(MediaRecorder.AudioSource.MIC, samplingRate, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, managerBufferSize);

recorder.startRecording();

player.play();

//record first packet

audioShorts = new short[1000];

shortsRead = recorder.read(audioShorts, 0, audioShorts.length);

//convert shorts to bytes to send

audioBytes = new byte[shortsRead*2];

ByteBuffer.wrap(audioBytes).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().put(audioShorts);

//send bytes

packet = new DatagramPacket(audioBytes, audioBytes.length);

socket.send(packet);

while (!this.isInterrupted()){

//recieve packet/bytes (received audio data should have echo cancelled already)

recvBytes = new byte[2000];

packet = new DatagramPacket(recvBytes, recvBytes.length);

socket.receive(packet);

//convert bytes to shorts

recvShorts = new short[packet.getLength()/2];

ByteBuffer.wrap(packet.getData(), 0, packet.getLength()).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(recvShorts);

//play shorts

player.write(recvShorts, 0, recvShorts.length);

//record shorts

recordedShorts = new short[1000];

shortsRead = recorder.read(recordedShorts, 0, recordedShorts.length);

//send played and recorded shorts into speex,

//returning audio data with the echo removed

filteredShorts = nativeMethod_speexEchoCancel(recordedShorts, recvShorts);

//convert filtered shorts to bytes

audioBytes = new byte[shortsRead*2];

ByteBuffer.wrap(audioBytes).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().put(filteredShorts);

//send off bytes

packet = new DatagramPacket(audioBytes, audioBytes.length);

socket.send(packet);

}//end of while loop

}

这是相关的NDK / JNI代码：

void nativeMethod_initEchoState(JNIEnv *env, jobject jobj, jint frameSize, jint filterLength){

echo_state = speex_echo_state_init(frameSize, filterLength);

}

jshortArray nativeMethod_speexEchoCancel(JNIEnv *env, jobject jObj, jshortArray input_frame, jshortArray echo_frame){

//create native shorts from java shorts

jshort *native_input_frame = (*env)->GetShortArrayElements(env, input_frame, NULL);

jshort *native_echo_frame = (*env)->GetShortArrayElements(env, echo_frame, NULL);

//allocate memory for output data

jint length = (*env)->GetArrayLength(env, input_frame);

jshortArray temp = (*env)->NewShortArray(env, length);

jshort *native_output_frame = (*env)->GetShortArrayElements(env, temp, 0);

//call echo cancellation

speex_echo_cancellation(echo_state, native_input_frame, native_echo_frame, native_output_frame);

//convert native output to java layer output

jshortArray output_shorts = (*env)->NewShortArray(env, length);

(*env)->SetShortArrayRegion(env, output_shorts, 0, length, native_output_frame);

//cleanup and return

(*env)->ReleaseShortArrayElements(env, input_frame, native_input_frame, 0);

(*env)->ReleaseShortArrayElements(env, echo_frame, native_echo_frame, 0);

(*env)->ReleaseShortArrayElements(env, temp, native_output_frame, 0);

return output_shorts;

}

这些代码运行良好,音频数据肯定是从android-to-android发送/接收/处理/播放.鉴于音频采样率为8000 Hz,数据包大小为2000bytes / 1000shorts,我发现需要一个1000的frameSize才能使播放的音频流畅. filterLength的大多数值(根据Speex doc也称为尾长)将运行,但似乎对回声消除没有影响.

有没有人理解足够的AEC为我提供一些关于实现或配置Speex的指示？谢谢阅读.