一、实现说明
OpenSL ES的录音要比播放简单一些，在创建好引擎后，再创建好录音接口基本就可以录音了。在这里我们做的是流式录音，所以需要用至少2个buffer来缓存录制好的PCM数据，这里我们可以动态创建一个二维数组，里面有2个buffer，然后每次录音取出一个，录制好后再写入文件就可以了，2个buffer依次来存储PCM数据，这样就可以连续录制流式音频数据了，二维数组里面自己维护了一个索引，来标识当前处于哪个buffer录制状态，暴露给外部的只是调用方法而已，细节对外也是隐藏的。
二、编码实现
1、编写缓存buffer队列：RecordBuffer.h、RecordBuffer.cpp
#ifndef OPENSLRECORD_RECORDBUFFER_H#define OPENSLRECORD_RECORDBUFFER_H class RecordBuffer { public: short **buffer; int index = -1;public: RecordBuffer(int buffersize); ~RecordBuffer(); /** * 得到一个新的录制buffer * @return */ short* getRecordBuffer(); /** * 得到当前录制buffer * @return */ short* getNowBuffer();}; #endif //OPENSLRECORD_RECORDBUFFER_H #include "RecordBuffer.h" RecordBuffer::RecordBuffer(int buffersize) { buffer = new short *[2]; for(int i = 0; i < 2; i++) { buffer[i] = new short[buffersize]; }} RecordBuffer::~RecordBuffer() {} short *RecordBuffer::getRecordBuffer() { index++; if(index > 1) { index = 0; } return buffer[index];} short *RecordBuffer::getNowBuffer() { return buffer[index];} 这个队列其实就是PCM存储的buffer，getRecordBuffer()为即将要录入PCM数据的buffer，getNowBuffer()是当前录制好的PCM数据的buffer，可以写入文件，即我们得到的PCM数据。
2、使用OpenSL ES录制PCM数据
过程分为：创建引擎->初始化IO设备（自动检测麦克风等音频输入设备）->设置缓存队列->设置录制PCM数据规格->设置录音器接口->设置队列接口并设置录音状态为录制->开始录音。
const char *path = env->GetStringUTFChars(path_, 0); /** * PCM文件 */ pcmFile = fopen(path, "w"); /** * PCMbuffer队列 */ recordBuffer = new RecordBuffer(RECORDER_FRAMES * 2); SLresult result; /** * 创建引擎对象 */ result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL); result = (*engineObject)->Realize(engineObject, SL_BOOLEAN_FALSE); result = (*engineObject)->GetInterface(engineObject, SL_IID_ENGINE, &engineEngine); /** * 设置IO设备（麦克风） */ SLDataLocator_IODevice loc_dev = {SL_DATALOCATOR_IODEVICE, SL_IODEVICE_AUDIOINPUT, SL_DEFAULTDEVICEID_AUDIOINPUT, NULL}; SLDataSource audioSrc = {&loc_dev, NULL}; /** * 设置buffer队列 */ SLDataLocator_AndroidSimpleBufferQueue loc_bq = {SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, 2}; /** * 设置录制规格：PCM、2声道、44100HZ、16bit */ SLDataFormat_PCM format_pcm = {SL_DATAFORMAT_PCM, 2, SL_SAMPLINGRATE_44_1, SL_PCMSAMPLEFORMAT_FIXED_16, SL_PCMSAMPLEFORMAT_FIXED_16, SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT, SL_BYTEORDER_LITTLEENDIAN}; SLDataSink audioSnk = {&loc_bq, &format_pcm}; const SLInterfaceID id[1] = {SL_IID_ANDROIDSIMPLEBUFFERQUEUE}; const SLboolean req[1] = {SL_BOOLEAN_TRUE}; /** * 创建录制器 */ result = (*engineEngine)->CreateAudioRecorder(engineEngine, &recorderObject, &audioSrc, &audioSnk, 1, id, req); if (SL_RESULT_SUCCESS != result) { return; } result = (*recorderObject)->Realize(recorderObject, SL_BOOLEAN_FALSE); if (SL_RESULT_SUCCESS != result) { return; } result = (*recorderObject)->GetInterface(recorderObject, SL_IID_RECORD, &recorderRecord); result = (*recorderObject)->GetInterface(recorderObject, SL_IID_ANDROIDSIMPLEBUFFERQUEUE, &recorderBufferQueue); finished = false; result = (*recorderBufferQueue)->Enqueue(recorderBufferQueue, recordBuffer->getRecordBuffer(), recorderSize); result = (*recorderBufferQueue)->RegisterCallback(recorderBufferQueue, bqRecorderCallback, NULL); LOGD("开始录音"); /** * 开始录音 */ (*recorderRecord)->SetRecordState(recorderRecord, SL_RECORDSTATE_RECORDING); env->ReleaseStringUTFChars(path_, path); 录音回调如下：
void bqRecorderCallback(SLAndroidSimpleBufferQueueItf bq, void *context){ // for streaming recording, here we would call Enqueue to give recorder the next buffer to fill // but instead, this is a one-time buffer so we stop recording LOGD("record size is %d", recorderSize); fwrite(recordBuffer->getNowBuffer(), 1, recorderSize, pcmFile); if(finished) { (*recorderRecord)->SetRecordState(recorderRecord, SL_RECORDSTATE_STOPPED); fclose(pcmFile); LOGD("停止录音"); } else{ (*recorderBufferQueue)->Enqueue(recorderBufferQueue, recordBuffer->getRecordBuffer(), recorderSize); }} 这样就完成了OPenSL ES的PCM音频数据录制，我们这里拿到了录制的PCM数据可以用mediacodec或ffmpeg来编码成aac格式的音频，也可以直接用推流到服务器来实现音频直播。
完整代码如下：
#include#include #include "AndroidLog.h"#include "RecordBuffer.h"#include "unistd.h" extern "C"{#include #include } //引擎接口static SLObjectItf engineObject = NULL;//引擎对象static SLEngineItf engineEngine; //录音器接口static SLObjectItf recorderObject = NULL;//录音器对象static SLRecordItf recorderRecord;//缓冲队列static SLAndroidSimpleBufferQueueItf recorderBufferQueue; //录制大小设为4096#define RECORDER_FRAMES (2048)static unsigned recorderSize = RECORDER_FRAMES * 2; //PCM文件FILE *pcmFile;//录音bufferRecordBuffer *recordBuffer; bool finished = false; void bqRecorderCallback(SLAndroidSimpleBufferQueueItf bq, void *context){ // for streaming recording, here we would call Enqueue to give recorder the next buffer to fill // but instead, this is a one-time buffer so we stop recording LOGD("record size is %d", recorderSize); fwrite(recordBuffer->getNowBuffer(), 1, recorderSize, pcmFile); if(finished) { (*recorderRecord)->SetRecordState(recorderRecord, SL_RECORDSTATE_STOPPED); fclose(pcmFile); LOGD("停止录音"); } else{ (*recorderBufferQueue)->Enqueue(recorderBufferQueue, recordBuffer->getRecordBuffer(), recorderSize); }} extern "C"JNIEXPORT void JNICALLJava_com_renhui_openslrecord_MainActivity_rdSound(JNIEnv *env, jobject instance, jstring path_) { const char *path = env->GetStringUTFChars(path_, 0); /** * PCM文件 */ pcmFile = fopen(path, "w"); /** * PCMbuffer队列 */ recordBuffer = new RecordBuffer(RECORDER_FRAMES * 2); SLresult result; /** * 创建引擎对象 */ result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL); result = (*engineObject)->Realize(engineObject, SL_BOOLEAN_FALSE); result = (*engineObject)->GetInterface(engineObject, SL_IID_ENGINE, &engineEngine); /** * 设置IO设备（麦克风） */ SLDataLocator_IODevice loc_dev = {SL_DATALOCATOR_IODEVICE, SL_IODEVICE_AUDIOINPUT, SL_DEFAULTDEVICEID_AUDIOINPUT, NULL}; SLDataSource audioSrc = {&loc_dev, NULL}; /** * 设置buffer队列 */ SLDataLocator_AndroidSimpleBufferQueue loc_bq = {SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, 2}; /** * 设置录制规格：PCM、2声道、44100HZ、16bit */ SLDataFormat_PCM format_pcm = {SL_DATAFORMAT_PCM, 2, SL_SAMPLINGRATE_44_1, SL_PCMSAMPLEFORMAT_FIXED_16, SL_PCMSAMPLEFORMAT_FIXED_16, SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT, SL_BYTEORDER_LITTLEENDIAN}; SLDataSink audioSnk = {&loc_bq, &format_pcm}; const SLInterfaceID id[1] = {SL_IID_ANDROIDSIMPLEBUFFERQUEUE}; const SLboolean req[1] = {SL_BOOLEAN_TRUE}; /** * 创建录制器 */ result = (*engineEngine)->CreateAudioRecorder(engineEngine, &recorderObject, &audioSrc, &audioSnk, 1, id, req); if (SL_RESULT_SUCCESS != result) { return; } result = (*recorderObject)->Realize(recorderObject, SL_BOOLEAN_FALSE); if (SL_RESULT_SUCCESS != result) { return; } result = (*recorderObject)->GetInterface(recorderObject, SL_IID_RECORD, &recorderRecord); result = (*recorderObject)->GetInterface(recorderObject, SL_IID_ANDROIDSIMPLEBUFFERQUEUE, &recorderBufferQueue); finished = false; result = (*recorderBufferQueue)->Enqueue(recorderBufferQueue, recordBuffer->getRecordBuffer(), recorderSize); result = (*recorderBufferQueue)->RegisterCallback(recorderBufferQueue, bqRecorderCallback, NULL); LOGD("开始录音"); /** * 开始录音 */ (*recorderRecord)->SetRecordState(recorderRecord, SL_RECORDSTATE_RECORDING); env->ReleaseStringUTFChars(path_, path);}extern "C"JNIEXPORT void JNICALLJava_com_renhui_openslrecord_MainActivity_rdStop(JNIEnv *env, jobject instance) { // TODO if(recorderRecord != NULL) { finished = true; }}
三、验证录制成果
有两种方法：
1. 使用的demo进行播放。
2. 使用 ffplay 命令播放，命令为：ffplay -f s16le -ar 44100 -ac 2 temp.pcm （命令由来：在录制代码里的参数为录制规格：PCM、2声道、44100HZ、16bit）
四、参考源码