Android音視頻開發—AudioRecord實作錄音功能

簡介

AudioRecord類管理Java應用程式的音瞥澩，以便從平臺的音頻輸入硬體錄制音頻，

AudioRecord錄制的是PCM格式的音頻檔案，需要用AudioTrack來播放(下一期介紹)，AudioTrack比MediaRecorder更接近底層、更專業，

實作步驟及決議

1、添加權限

 <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" />

分別是錄音權限；讀、寫外部存盤器權限

2、撰寫基于AudioRecord的錄音工具類

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的錄音工具類
 */
public class AudioRecordTool{
    private AudioRecord audioRecord;
    private int recordBufSize = 0;
    private byte data[];
    private PcmToWavTool tool;
    private boolean isRecording = false;
    //錄音得到的檔案 的儲存位置及檔案名
    private final String pcmFileName = Environment.getExternalStorageDirectory() + "/Download/record.pcm";
    //轉換成wav檔案后新檔案的存盤位置及檔案名
    private final String wavFileName = Environment.getExternalStorageDirectory() + "/Download/record1.wav";
    // 音頻源：音頻輸入-麥克風
    private final static int AUDIO_INPUT = MediaRecorder.AudioSource.MIC;
    // 采樣率：音頻的采樣頻率，每秒鐘能夠采樣的次數，采樣率越高，音質越高
    // 44100是目前的標準，但是某些設備仍然支持22050，16000，11025
    // 采樣頻率一般共分為22.05KHz、44.1KHz、48KHz三個等級
    private final static int AUDIO_SAMPLE_RATE = 44100;

    // 聲道設定：android支持雙聲道立體聲和單聲道，MONO單聲道，STEREO立體聲
    private final static int AUDIO_CHANNEL = AudioFormat.CHANNEL_IN_MONO;

    // 編碼制式和采樣大小：采集來的資料當然使用PCM編碼
    // (脈沖代碼調制編碼，即PCM編碼，PCM通過抽樣、量化、編碼三個步驟將連續變化的模擬信號轉換為數字編碼，)
    // android支持的采樣大小16bit 或者8bit，當然采樣大小越大，那么資訊量越多，音質也越高，現在主流的采樣
    // 大小都是16bit，在低質量的語音傳輸的時候8bit 足夠了，
    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
        //構造方法，傳入的引數上面在有決議
        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);
    }
    //開始錄音
    public void start(){
         Log.i("AUDIO","開始錄音");
         isRecording = true;
         //呼叫startRecording()方法開始錄制
         audioRecord.startRecording();
         MyThread myThread = new MyThread();
         myThread.start();
    }
    //停止錄音
    public void stop(){
        isRecording = false;
        if (audioRecord != null){
            Log.i("AUDIO","停止錄音");
            //呼叫stop()方法停止錄制
            audioRecord.stop();
            //呼叫release() 釋放本機錄音資源，
            audioRecord.release();
            audioRecord = null;
        }
        //利用自定義工具類將pcm格式的檔案轉換為wav格式檔案才能進行播放
        tool.pcmToWav(pcmFileName,wavFileName);
    }
    private class MyThread extends Thread{
        @Override
        public void run() {
            super.run();
            FileOutputStream os = null;
            try {
                //如果檔案不存在，就創建檔案
                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) {
                    //呼叫read(@NonNull byte[] audioData, int offsetInBytes, int sizeInBytes)方法
                    // 從音頻硬體讀取音頻資料，以便記錄到位元組陣列中，
                    int read = audioRecord.read(data, 0, recordBufSize);

                    // 如果讀取音頻資料沒有出現錯誤，就將資料寫入到檔案
                    if (AudioRecord.ERROR_INVALID_OPERATION != read) {
                        try {
                            os.write(data);
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }

                try {
                    //關閉檔案
                    os.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

3、撰寫pcm格式轉化為wav格式的工具類，播放器才能進行播放

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格式轉化為wav格式的工具類
 * PCM編碼是直接存盤聲波采樣被量化后所產生的非壓縮資料，故被視為單純的無損耗編碼格式，其優點是可獲得高質量的音頻信號
 * WAV是最常見的聲音檔案格式之一
 */
public class PcmToWavTool {
        /**
         * 快取的音頻大小
         */
        private int mBufferSize;
        /**
         * 采樣率
         */
        private int mSampleRate;
        /**
         * 聲道數
         */
        private int mChannel;


        /**
         * @param sampleRate sample rate、采樣率
         * @param channel channel、聲道
         * @param encoding Audio data format、音頻格式
         */
        PcmToWavTool(int sampleRate, int channel, int encoding) {
            this.mSampleRate = sampleRate;
            this.mChannel = channel;
            this.mBufferSize = AudioRecord.getMinBufferSize(mSampleRate, mChannel, encoding);
        }


        /**
         * pcm檔案轉wav檔案
         *
         * @param inFilename 源檔案路徑
         * @param outFilename 目標檔案路徑
         */
        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檔案頭
         */
        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、撰寫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;

/**
 * 錄音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();
    }
}

頁面只有2個按鈕，一個開始錄音按鈕，一個停止錄音按鈕

測驗

手機有檔案，能播放，