android - 音频(录制 - 回放)Android 异常回声

Question

我正在使用以下代码来实现实时录制和回放系统:

import android.media.*;

class Rec {

static boolean m_isRun = true;

static int buffersize, SAMPLE_RATE = 22050;

public static void loopback()

{
    AudioRecord m_record = null;

    AudioTrack m_track = null;

    // Prepare the AudioRecord & AudioTrack

    try {

        buffersize = AudioRecord.getMinBufferSize(SAMPLE_RATE,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_16BIT);

        //Log.i(LOG_TAG,"Initializing Audio Record and Audio Playing objects");

        m_record = new AudioRecord(MediaRecorder.AudioSource.MIC,
                SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_16BIT, buffersize * 1);

        m_track = new AudioTrack(AudioManager.STREAM_MUSIC,
                SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_16BIT, buffersize * 1,
                AudioTrack.MODE_STREAM);

        m_track.setPlaybackRate(SAMPLE_RATE);
    } catch (Throwable t) {
        // Log.e("Error", "Initializing Audio Record and Play objects Failed "+t.getLocalizedMessage());
    }

    m_record.startRecording();
    //Log.i(LOG_TAG,"Audio Recording started");
    m_track.play();
    //Log.i(LOG_TAG,"Audio Playing started");

    byte buffer[] = new byte[buffersize];

    while (m_isRun)

    {
        m_record.read(buffer, 0, buffer.length);

        m_track.write(buffer, 0, buffer.length);

    }

}

public static void do_loopback() {
    new Thread(new Runnable() {
        public void run() {
            loopback();
        }
    }).start();
}
}

我已经插上了耳机。

如您所见，输入音频来自麦克风(即来自智能手机内的录音芯片)，而输出音频仅路由至耳机(由于 AudioTrack 的 STREAM_MUSIC 流类型)。

但我的问题是，它会在播放过程中产生回声。我认为，Echo 不是由于录制播放音频造成的，因为播放音频只能通过插入的耳机播放。而且耳机放置在距离录音手机近 1 到 2 英尺的地方。

那么是什么导致了回声？

Answer 1

尝试将 minBuffer 和 MediaRecorder 设置为“AudioFormat.CHANNEL_IN_STEREO”，我还将 AudioTrack 设置为“AudioTrack.PERFORMANCE_MODE_LOW_LATENCY”和“AudioFormat.CHANNEL_OUT_STEREO”，在我的例子中，这对我来说很有效，声音输出清晰。

    boolean isRecording;
private int minBuffer;
private int sampleRate = 44100;

void loop() {
    AudioRecord mAudioRecord = null;
    AudioTrack mAudioTrack = null;
    try {
        minBuffer = AudioRecord.getMinBufferSize(sampleRate,
                AudioFormat.CHANNEL_IN_STEREO,
                AudioFormat.ENCODING_PCM_16BIT);


        Log.d(TAG, "loop: " + minBuffer);

        mAudioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC,
                sampleRate,
                AudioFormat.CHANNEL_IN_STEREO,
                AudioFormat.ENCODING_PCM_16BIT, minBuffer);


        mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
                sampleRate,
                AudioFormat.CHANNEL_OUT_STEREO,
                AudioFormat.ENCODING_PCM_16BIT,
                minBuffer,
                AudioTrack.PERFORMANCE_MODE_LOW_LATENCY);

        mAudioTrack.setPlaybackRate(sampleRate);

    } catch (Exception e) {
        Log.d(TAG, "startStream: " + e.getMessage());
    } finally {
        try {
            mAudioRecord.startRecording();
        } catch (IllegalStateException e) {
            Log.d(TAG, "loop: " + e.getMessage());
        }
    }

    mAudioTrack.play();

    byte[] buffer = new byte[minBuffer];

    while (isRecording) {
        mAudioRecord.read(buffer, 0, buffer.length);

        mAudioTrack.write(buffer, 0, buffer.length);
    }
}