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Android音视频之AudioRecord录音(一)

程序员文章站 2022-08-10 15:20:39
在音视频开发中，录音当然是必不可少的。首先我们要学会单独的录音功能，当然这里说的录音是指用AudioRecord来录音，读取录音原始数据，读到的就是所谓的PCM数据。对于录音来说，最重要的几个参数要搞明白： 1、simpleRate采样率，采样率就是采样频率，每秒钟记录多少个样本。 2、channe ......

在音视频开发中，录音当然是必不可少的。首先我们要学会单独的录音功能，当然这里说的录音是指用audiorecord来录音，读取录音原始数据，读到的就是所谓的pcm数据。对于录音来说，最重要的几个参数要搞明白：

1、simplerate采样率，采样率就是采样频率，每秒钟记录多少个样本。

2、channelconfig通道配置，其实就是所谓的单通道，双通道之类的，audioformat.channel_in_mono单通道，audioformat.channel_in_stereo双通道，这里只列了这两种，还有其它的，可自行查阅。

3、audioformat音频格式，其实就是采样的精度，每个样本的位数，audioformat.encoding_pcm_8bit每个样本占8位，audioformat.encoding_pcm_16bit每个样本占16位，这里也只用了这两个，别的没研究。

在学习过程中会用到的一些参数，我这里封装了一个类，如下

public class audioparams {

    enum format {
        single_8_bit, double_8_bit, single_16_bit, double_16_bit
    }

    private format format;
    int simplerate;

    audioparams(int simplerate, format f) {
        this.simplerate = simplerate;
        this.format = f;
    }

    audioparams(int simplerate, int channelcount, int bits) {
        this.simplerate = simplerate;
        set(channelcount, bits);
    }

    int getbits() {
        return (format == format.single_8_bit || format == format.double_8_bit) ? 8 : 16;
    }

    int getencodingformat() {
        return (format == format.single_8_bit || format == format.double_8_bit) ? audioformat.encoding_pcm_8bit :
            audioformat.encoding_pcm_16bit;
    }

    int getchannelcount() {return (format == format.single_8_bit || format == format.single_16_bit) ? 1 : 2;}

    int getchannelconfig() {
        return (format == format.single_8_bit || format == format.single_16_bit) ? audioformat.channel_in_mono :
            audioformat.channel_in_stereo;
    }

    int getoutchannelconfig() {
        return (format == format.single_8_bit || format == format.single_16_bit) ? audioformat.channel_out_mono :
            audioformat.channel_out_stereo;
    }

    void set(int channelcount, int bits) {
        if ((channelcount != 1 && channelcount != 2) || (bits != 8 && bits != 16)) {
            throw new illegalargumentexception("不支持其它格式 channelcount=$channelcount bits=$bits");
        }
        if (channelcount == 1) {
            if (bits == 8) {
                format = format.single_8_bit;
            } else {
                format = format.single_16_bit;
            }
        } else {
            if (bits == 8) {
                format = format.double_8_bit;
            } else {
                format = format.double_16_bit;
            }
        }
    }
}

这里固定使用了单通道8位，双通道8位，单通道16位，双通道16位，所以用了枚举来限制。

为了方便把录音数据拿出来显示、存储，这里写了一个回调方法如下

    public interface recordcallback {
        /**
         * 数据回调
         *
         * @param bytes 数据
         * @param len   数据有效长度，-1时表示数据结束
         */
        void onrecord(byte[] bytes, int len);
    }

有了这些参数，现在就可以录音了，先看一下样例

    public void startrecord(audioparams params, recordcallback callback) {
        int simplerate = params.simplerate;
        int channelconfig = params.getchannelconfig();
        int audioformat = params.getencodingformat();
        // 根据audiorecord提供的api拿到最小缓存大小
        int buffersize = audiorecord.getminbuffersize(simplerate, channelconfig, audioformat);
        //创建record对象
        record = new audiorecord(mediarecorder.audiosource.mic, simplerate, channelconfig, audioformat, buffersize);
        recordthread = new thread(() -> {
            byte[] buffer = new byte[buffersize];
            record.startrecording();
            recording = true;
            while (recording) {
                int read = record.read(buffer, 0, buffersize);
                // 将数据回调到外部
                if (read > 0 && callback != null) {
                    callback.onrecord(buffer, read);
                }
            }
            if (callback != null) {
                // len 为-1时表示结束
                callback.onrecord(buffer, -1);
                recording = false;
            }
            //释放资源
            release();
        });
        recordthread.start();
    }

这个方法就是简单的采集音频数据，这个数据就是最原始的pcm数据。

拿到pcm数据以后，如果直接保存到文件是无法直接播放的，因为这只是一堆数据，没有任何格式说明，如果想让普通播放器可以播放，需要在文件中加入文件头，来告诉播放器这个数据的格式，这里是直接保存成wav格式的数据。下面就是加入wav格式文件头的方法

    private static byte[] getwavefileheader(int totaldatalen, int samplerate, int channelcount, int bits) {
        byte[] header = new byte[44];
        // riff/wave header
        header[0] = 'r';
        header[1] = 'i';
        header[2] = 'f';
        header[3] = 'f';

        int filelength = totaldatalen + 36;
        header[4] = (byte) (filelength & 0xff);
        header[5] = (byte) (filelength >> 8 & 0xff);
        header[6] = (byte) (filelength >> 16 & 0xff);
        header[7] = (byte) (filelength >> 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;

        // pcm format = 1
        header[20] = 1;
        header[21] = 0;
        header[22] = (byte) channelcount;
        header[23] = 0;

        header[24] = (byte) (samplerate & 0xff);
        header[25] = (byte) (samplerate >> 8 & 0xff);
        header[26] = (byte) (samplerate >> 16 & 0xff);
        header[27] = (byte) (samplerate >> 24 & 0xff);

        int byterate = samplerate * bits * channelcount / 8;
        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) (channelcount * bits / 8);
        header[33] = 0;
        // bits per sample
        header[34] = (byte) bits;
        header[35] = 0;
        //data
        header[36] = 'd';
        header[37] = 'a';
        header[38] = 't';
        header[39] = 'a';
        header[40] = (byte) (totaldatalen & 0xff);
        header[41] = (byte) (totaldatalen >> 8 & 0xff);
        header[42] = (byte) (totaldatalen >> 16 & 0xff);
        header[43] = (byte) (totaldatalen >> 24 & 0xff);
        return header;
    }

根据几个参数设置一下文件头，然后直接写入录音采集到的pcm数据，就可被正常播放了。wav文件头格式定义，可查看或自行百度。

如果想要通过audiorecord录音直接保存到文件，可参考下面方法

    public void startrecord(string filepath, audioparams params, recordcallback callback) {
        int channelcount = params.getchannelcount();
        int bits = params.getbits();

        final boolean storefile = filepath != null && !filepath.isempty();

        startrecord(params, (bytes, len) -> {
            if (storefile) {
                if (file == null) {
                    file f = new file(filepath);
                    if (f.exists()) {
                        f.delete();
                    }
                    try {
                        file = new randomaccessfile(f, "rw");
                        file.write(getwavefileheader(0, params.simplerate, channelcount, bits));
                    } catch (ioexception e) {
                        e.printstacktrace();
                    }
                }
                if (len > 0) {
                    try {
                        file.write(bytes, 0, len);
                    } catch (ioexception e) {
                        e.printstacktrace();
                    }
                } else {
                    try {
                        // 因为在前面已经写入头信息，所以这里要减去头信息才是数据的长度
                        int length = (int) file.length() - 44;
                        file.seek(0);
                        file.write(getwavefileheader(length, params.simplerate, channelcount, bits));
                        file.close();
                    } catch (ioexception e) {
                        e.printstacktrace();
                    }
                }
            }
            if (callback != null) {
                callback.onrecord(bytes, len);
            }
        });
    }

先通过randomaccessfile创建文件，先写入文件头，由于暂时我们不知道会录多长，有多少pcm数据，长度先用0表示，等录音结束后，通过seek(int)方法重新写入文件头信息，也可以先把pcm数据保存到临时文件，然后再写入到一个新的文件中，这里就不举例说明了。

最后放入完整类的代码

package cn.sskbskdrin.record.audio;

import android.media.audiorecord;
import android.media.mediarecorder;

import java.io.file;
import java.io.ioexception;
import java.io.randomaccessfile;

/**
 * @author sskbskdrin
 * @date 2019/april/3
 */
public class audiorecordmanager {

    private audioparams default_format = new audioparams(8000, 1, 16);

    private audiorecord record;

    private thread recordthread;

    private boolean recording = false;

    private randomaccessfile file;

    public void startrecord(string filepath, recordcallback callback) {
        startrecord(filepath, default_format, callback);
    }

    public void startrecord(string filepath, audioparams params, recordcallback callback) {
        int channelcount = params.getchannelcount();
        int bits = params.getbits();

        final boolean storefile = filepath != null && !filepath.isempty();

        startrecord(params, (bytes, len) -> {
            if (storefile) {
                if (file == null) {
                    file f = new file(filepath);
                    if (f.exists()) {
                        f.delete();
                    }
                    try {
                        file = new randomaccessfile(f, "rw");
                        file.write(getwavefileheader(0, params.simplerate, channelcount, bits));
                    } catch (ioexception e) {
                        e.printstacktrace();
                    }
                }
                if (len > 0) {
                    try {
                        file.write(bytes, 0, len);
                    } catch (ioexception e) {
                        e.printstacktrace();
                    }
                } else {
                    try {
                        // 因为在前面已经写入头信息，所以这里要减去头信息才是数据的长度
                        int length = (int) file.length() - 44;
                        file.seek(0);
                        file.write(getwavefileheader(length, params.simplerate, channelcount, bits));
                        file.close();
                    } catch (ioexception e) {
                        e.printstacktrace();
                    }
                }
            }
            if (callback != null) {
                callback.onrecord(bytes, len);
            }
        });
    }

    public void startrecord(audioparams params, recordcallback callback) {
        int simplerate = params.simplerate;
        int channelconfig = params.getchannelconfig();
        int audioformat = params.getencodingformat();
        // 根据audiorecord提供的api拿到最小缓存大小
        int buffersize = audiorecord.getminbuffersize(simplerate, channelconfig, audioformat);
        //创建record对象
        record = new audiorecord(mediarecorder.audiosource.mic, simplerate, channelconfig, audioformat, buffersize);
        recordthread = new thread(() -> {
            byte[] buffer = new byte[buffersize];
            record.startrecording();
            recording = true;
            while (recording) {
                int read = record.read(buffer, 0, buffersize);
                // 将数据回调到外部
                if (read > 0 && callback != null) {
                    callback.onrecord(buffer, read);
                }
            }
            if (callback != null) {
                // len 为-1时表示结束
                callback.onrecord(buffer, -1);
                recording = false;
            }
            //释放资源
            release();
        });
        recordthread.start();
    }

    public void stop() {
        recording = false;
    }

    public void release() {
        recording = false;
        if (record != null) {
            record.stop();
            record.release();
        }
        record = null;
        file = null;
        recordthread = null;
    }

    private static byte[] getwavefileheader(int totaldatalen, int samplerate, int channelcount, int bits) {
        byte[] header = new byte[44];
        // riff/wave header
        header[0] = 'r';
        header[1] = 'i';
        header[2] = 'f';
        header[3] = 'f';

        int filelength = totaldatalen + 36;
        header[4] = (byte) (filelength & 0xff);
        header[5] = (byte) (filelength >> 8 & 0xff);
        header[6] = (byte) (filelength >> 16 & 0xff);
        header[7] = (byte) (filelength >> 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;

        // pcm format = 1
        header[20] = 1;
        header[21] = 0;
        header[22] = (byte) channelcount;
        header[23] = 0;

        header[24] = (byte) (samplerate & 0xff);
        header[25] = (byte) (samplerate >> 8 & 0xff);
        header[26] = (byte) (samplerate >> 16 & 0xff);
        header[27] = (byte) (samplerate >> 24 & 0xff);

        int byterate = samplerate * bits * channelcount / 8;
        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) (channelcount * bits / 8);
        header[33] = 0;
        // bits per sample
        header[34] = (byte) bits;
        header[35] = 0;
        //data
        header[36] = 'd';
        header[37] = 'a';
        header[38] = 't';
        header[39] = 'a';
        header[40] = (byte) (totaldatalen & 0xff);
        header[41] = (byte) (totaldatalen >> 8 & 0xff);
        header[42] = (byte) (totaldatalen >> 16 & 0xff);
        header[43] = (byte) (totaldatalen >> 24 & 0xff);
        return header;
    }

    public interface recordcallback {
        /**
         * 数据回调
         *
         * @param bytes 数据
         * @param len   数据有效长度，-1时表示数据结束
         */
        void onrecord(byte[] bytes, int len);
    }
}

 

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