Android音视频开发—AudioRecord实现录音功能

简介

AudioRecord类管理Java应用程序的音频资源，以便从平台的音频输入硬件录制音频。

AudioRecord录制的是PCM格式的音频文件，需要用AudioTrack来播放(下一期介绍)，AudioTrack比MediaRecorder更接近底层、更专业。

实现步骤及解析

1、添加权限

 <uses-permission android:name="android.permission.RECORD_AUDIO" />
 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

分别是录音权限；读、写外部存储器权限

2、编写基于AudioRecord的录音工具类

AudioRecordTool.java

package com.audioandvideo.two.Tool;

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.os.Environment;
import android.util.Log;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * 基于AudioRecord的录音工具类
 */
public class AudioRecordTool{
    
    
    private AudioRecord audioRecord;
    private int recordBufSize = 0;
    private byte data[];
    private PcmToWavTool tool;
    private boolean isRecording = false;
    //录音得到的文件 的储存位置及文件名
    private final String pcmFileName = Environment.getExternalStorageDirectory() + "/Download/record.pcm";
    //转换成wav文件后新文件的存储位置及文件名
    private final String wavFileName = Environment.getExternalStorageDirectory() + "/Download/record1.wav";
    // 音频源：音频输入-麦克风
    private final static int AUDIO_INPUT = MediaRecorder.AudioSource.MIC;
    // 采样率：音频的采样频率，每秒钟能够采样的次数，采样率越高，音质越高
    // 44100是目前的标准，但是某些设备仍然支持22050，16000，11025
    // 采样频率一般共分为22.05KHz、44.1KHz、48KHz三个等级
    private final static int AUDIO_SAMPLE_RATE = 44100;

    // 声道设置：android支持双声道立体声和单声道。MONO单声道，STEREO立体声
    private final static int AUDIO_CHANNEL = AudioFormat.CHANNEL_IN_MONO;

    // 编码制式和采样大小：采集来的数据当然使用PCM编码
    // (脉冲代码调制编码，即PCM编码。PCM通过抽样、量化、编码三个步骤将连续变化的模拟信号转换为数字编码。)
    // android支持的采样大小16bit 或者8bit。当然采样大小越大，那么信息量越多，音质也越高，现在主流的采样
    // 大小都是16bit，在低质量的语音传输的时候8bit 足够了。
    private final static int AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
   
    //初始化
    public void createAudioRecord() {
    
    
        recordBufSize = AudioRecord.getMinBufferSize(AUDIO_SAMPLE_RATE, AUDIO_CHANNEL, AUDIO_ENCODING);  //audioRecord能接受的最小的buffer大小
        //构造方法，传入的参数上面在有解析
        audioRecord = new AudioRecord(AUDIO_INPUT, AUDIO_SAMPLE_RATE, AUDIO_CHANNEL, AUDIO_ENCODING, recordBufSize);
        data = new byte[recordBufSize];
        tool = new PcmToWavTool(AUDIO_SAMPLE_RATE,AUDIO_CHANNEL,AUDIO_ENCODING);
    }
    //开始录音
    public void start(){
    
    
         Log.i("AUDIO","开始录音");
         isRecording = true;
         //调用startRecording()方法开始录制
         audioRecord.startRecording();
         MyThread myThread = new MyThread();
         myThread.start();
    }
    //停止录音
    public void stop(){
    
    
        isRecording = false;
        if (audioRecord != null){
    
    
            Log.i("AUDIO","停止录音");
            //调用stop()方法停止录制
            audioRecord.stop();
            //调用release() 释放本机录音资源。
            audioRecord.release();
            audioRecord = null;
        }
        //利用自定义工具类将pcm格式的文件转换为wav格式文件才能进行播放
        tool.pcmToWav(pcmFileName,wavFileName);
    }
    private class MyThread extends Thread{
    
    
        @Override
        public void run() {
    
    
            super.run();
            FileOutputStream os = null;
            try {
    
    
                //如果文件不存在，就创建文件
                if(!new File(pcmFileName).exists()){
    
    
                    new File(pcmFileName).createNewFile();
                }
                os = new FileOutputStream(pcmFileName);
            } catch (FileNotFoundException e) {
    
    
                e.printStackTrace();
            } catch (IOException e) {
    
    
                e.printStackTrace();
            }

            if (null != os) {
    
    
                while (isRecording) {
    
    
                    //调用read(@NonNull byte[] audioData, int offsetInBytes, int sizeInBytes)方法
                    // 从音频硬件读取音频数据，以便记录到字节数组中。
                    int read = audioRecord.read(data, 0, recordBufSize);

                    // 如果读取音频数据没有出现错误，就将数据写入到文件
                    if (AudioRecord.ERROR_INVALID_OPERATION != read) {
    
    
                        try {
    
    
                            os.write(data);
                        } catch (IOException e) {
    
    
                            e.printStackTrace();
                        }
                    }
                }

                try {
    
    
                    //关闭文件
                    os.close();
                } catch (IOException e) {
    
    
                    e.printStackTrace();
                }
            }
        }
    }
}

3、编写pcm格式转化为wav格式的工具类，播放器才能进行播放

PcmToWavTool .java

package com.audioandvideo.two.Tool;

import android.media.AudioFormat;
import android.media.AudioRecord;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

/**pcm格式转化为wav格式的工具类
 * PCM编码是直接存储声波采样被量化后所产生的非压缩数据，故被视为单纯的无损耗编码格式，其优点是可获得高质量的音频信号
 * WAV是最常见的声音文件格式之一
 */
public class PcmToWavTool {
    
    
        /**
         * 缓存的音频大小
         */
        private int mBufferSize;
        /**
         * 采样率
         */
        private int mSampleRate;
        /**
         * 声道数
         */
        private int mChannel;


        /**
         * @param sampleRate sample rate、采样率
         * @param channel channel、声道
         * @param encoding Audio data format、音频格式
         */
        PcmToWavTool(int sampleRate, int channel, int encoding) {
    
    
            this.mSampleRate = sampleRate;
            this.mChannel = channel;
            this.mBufferSize = AudioRecord.getMinBufferSize(mSampleRate, mChannel, encoding);
        }


        /**
         * pcm文件转wav文件
         *
         * @param inFilename 源文件路径
         * @param outFilename 目标文件路径
         */
        public void pcmToWav(String inFilename, String outFilename) {
    
    
            FileInputStream in;
            FileOutputStream out;
            long totalAudioLen;
            long totalDataLen;
            long longSampleRate = mSampleRate;
            int channels = mChannel == AudioFormat.CHANNEL_IN_MONO ? 1 : 2;
            long byteRate = 16 * mSampleRate * channels / 8;
            byte[] data = new byte[mBufferSize];
            try {
    
    
                in = new FileInputStream(inFilename);
                out = new FileOutputStream(outFilename);
                totalAudioLen = in.getChannel().size();
                totalDataLen = totalAudioLen + 36;

                writeWaveFileHeader(out, totalAudioLen, totalDataLen,
                        longSampleRate, channels, byteRate);
                while (in.read(data) != -1) {
    
    
                    out.write(data);
                }
                in.close();
                out.close();
            } catch (IOException e) {
    
    
                e.printStackTrace();
            }
        }
        /**
         * 加入wav文件头
         */
        private void writeWaveFileHeader(FileOutputStream out, long totalAudioLen,
                                         long totalDataLen, long longSampleRate, int channels, long byteRate)
                throws IOException {
    
    
            byte[] header = new byte[44];
            // RIFF/WAVE header
            header[0] = 'R';
            header[1] = 'I';
            header[2] = 'F';
            header[3] = 'F';
            header[4] = (byte) (totalDataLen & 0xff);
            header[5] = (byte) ((totalDataLen >> 8) & 0xff);
            header[6] = (byte) ((totalDataLen >> 16) & 0xff);
            header[7] = (byte) ((totalDataLen >> 24) & 0xff);
            //WAVE
            header[8] = 'W';
            header[9] = 'A';
            header[10] = 'V';
            header[11] = 'E';
            // 'fmt ' chunk
            header[12] = 'f';
            header[13] = 'm';
            header[14] = 't';
            header[15] = ' ';
            // 4 bytes: size of 'fmt ' chunk
            header[16] = 16;
            header[17] = 0;
            header[18] = 0;
            header[19] = 0;
            // format = 1
            header[20] = 1;
            header[21] = 0;
            header[22] = (byte) channels;
            header[23] = 0;
            header[24] = (byte) (longSampleRate & 0xff);
            header[25] = (byte) ((longSampleRate >> 8) & 0xff);
            header[26] = (byte) ((longSampleRate >> 16) & 0xff);
            header[27] = (byte) ((longSampleRate >> 24) & 0xff);
            header[28] = (byte) (byteRate & 0xff);
            header[29] = (byte) ((byteRate >> 8) & 0xff);
            header[30] = (byte) ((byteRate >> 16) & 0xff);
            header[31] = (byte) ((byteRate >> 24) & 0xff);
            // block align
            header[32] = (byte) (2 * 16 / 8);
            header[33] = 0;
            // bits per sample
            header[34] = 16;
            header[35] = 0;
            //data
            header[36] = 'd';
            header[37] = 'a';
            header[38] = 't';
            header[39] = 'a';
            header[40] = (byte) (totalAudioLen & 0xff);
            header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
            header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
            header[43] = (byte) ((totalAudioLen >> 24) & 0xff);
            out.write(header, 0, 44);
        }

}

4、编写Activity

AudioRecordActivity.java

package com.audioandvideo.two.Activity;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.audioandvideo.R;
import com.audioandvideo.two.Tool.AudioRecordTool;

/**
 * 录音Activity
 */
public class AudioRecordActivity extends AppCompatActivity implements View.OnClickListener{
    
    
private Button btnStart;
private Button btnStop;
private AudioRecordTool audioRecordTool;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_audio_record);
        btnStart = findViewById(R.id.btn_start);
        btnStop = findViewById(R.id.btn_stop);
        audioRecordTool = new AudioRecordTool();
        //初始化
        audioRecordTool.createAudioRecord();
        btnStart.setOnClickListener(this);
        btnStop.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
    
    
        switch (v.getId()){
    
    
            case R.id.btn_start:
                audioRecordTool.start();
                break;
            case R.id.btn_stop:
                audioRecordTool.stop();
                break;
        }
    }

    @Override
    protected void onDestroy() {
    
    
        super.onDestroy();
        audioRecordTool.stop();
    }
}

页面只有2个按钮，一个开始录音按钮，一个停止录音按钮

测试

手机有文件，能播放。