Android音视频之AudioRecord录音(一)
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2022-05-03 12:01:02
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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