Android AudioRecord Android用AudioRecord进行录音
原心木 人气:0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,可点击这里查看或自行百度。
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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