书中示例源码地址

Android SDK提供了两套音频采集的API，分别是:MediaRecorder和AudioRecord。前者是一个更加上层的API，它可以直接对手机麦克风录入的音频数据进行编码压缩(如AMR,MP3等)，并存储为文件；后者更加接近底层，能够更加灵活地控制，其可以让开发者得到内存中的PCM音频流数据。如果想做一个简单的录音机，输出音频文件，则推荐使用MediaRecorder；如果需要对音频做进一步的算法处理，或者需要采用第三方的编码库进行编码压缩，又或者需要用到网络传输等场景中，那么只能使用AudioRecord或者OpenSL ES，其实MediaRecorder底层也是调用了AudioRecord与Android Framework层的AudioFlinger进行交互的。至于OpenSL ES，请参考另一篇文章音视频开发进阶指南(第四章)-OpenSL-ES播放PCM音频。

本章讲解如何使用AudioRecord录音音频，并使用AudioTrack播放

播放步骤

1. 初始化AudioRecord

private static final int SAMPLE_RATE = 44100;//采样率
private static final int CHANNEL_CONFIG_IN = AudioFormat.CHANNEL_IN_MONO;//通道配置
private static final int CHANNEL_CONFIG_OUT = AudioFormat.CHANNEL_OUT_MONO;//通道配置
private static final int ENCODING_FORMAT = AudioFormat.ENCODING_PCM_16BIT;//编码配置
private static final String PCM_FILE = "/mnt/sdcard/test.pcm";
private static final String TAG = "MainActivity";

int minBufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, CHANNEL_CONFIG_IN, ENCODING_FO
mAudioRecord = new AudioRecord(
        MediaRecorder.AudioSource.DEFAULT,//默认音频源
        SAMPLE_RATE,    //采样率
        CHANNEL_CONFIG_IN, //通道
        ENCODING_FORMAT,    //表示格式
        minBufferSize); //最小缓存
//开启录音
mAudioRecord.startRecording();

读取音频数据并写入文件

/**
 * 读取音频数据并写入文件
 */
private void startReadThread() {
    Log.d(TAG, "startReadThread");
    new Thread() {
        @Override
        public void run() {
            super.run();
            short[] buf = new short[1024];//一次读取的音频数据大小
            BufferedOutputStream bos = null;
            FileOutputStream fos = null;
            try {
                fos = new FileOutputStream(PCM_FILE);
                bos = new BufferedOutputStream(fos);
                while (mAudioRecord.read(buf, 0, buf.length) > 0) {
                    //把short转为字节数组
                    byte[] bytes = ArrayUtil.toByteArraySmallEnd(buf);
                    bos.write(bytes);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    bos.close();
                    fos.close();
                    if (mAudioRecord != null) {
                        mAudioRecord.stop();
                        mAudioRecord.release();
                        mAudioRecord = null;
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }.start();
}

使用AudioTrack进行播放

private void play() {
    File file = new File(PCM_FILE);
    if (!file.exists()) {
        Toast.makeText(this, "请先开始录音", Toast.LENGTH_SHORT).show();
        return;
    }
    int minBufferSize = AudioTrack.getMinBufferSize(SAMPLE_RATE, CHANNEL_CONFIG_OUT, ENCODI
    mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
            SAMPLE_RATE,
            CHANNEL_CONFIG_OUT,
            ENCODING_FORMAT,
            minBufferSize,
            AudioTrack.MODE_STREAM);
    mAudioTrack.play();
    new Thread() {
        @Override
        public void run() {
            super.run();
            FileInputStream fis = null;
            BufferedInputStream bis = null;
            byte[] buf = new byte[1024];
            try {
                fis = new FileInputStream(PCM_FILE);
                bis = new BufferedInputStream(fis);
                int read = 0;
                while ((read = bis.read(buf)) > 0) {
                    mAudioTrack.write(buf, 0, read);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    bis.close();
                    fis.close();
                    if (mAudioTrack != null) {
                        mAudioTrack.stop();
                        mAudioTrack.release();
                        mAudioTrack = null;
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }.start();
}

附上源码[AudioRecord-Test(https://github.com/dd-Dog/AudioRecord-Test.git)

代码比较简单，没有过多注释，如有问题，欢迎留言！