前言
本章主要讲述如何通过Android OpenSL 实现录制 PCM 音频数据。开发流程回顾可以看下笔者前面发布过的文章。
开发准备
1.在Android studo下面建立工程，在使用OpenSL ES的API之前，首先需要引入CMakeLists.txt里面添加依赖库和链接库，代码如下：
代码语言：txt复制find_library( # Sets the name of the path variable.
log-lib
android
# Specifies the name of the NDK library that
# you want CMake to locate.
log )
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
native-lib
OpenSLES
android
# Links the target library to the log library
# included in the NDK.
${log-lib} )2.同时添加静态库依赖的c 文件
代码语言：txt复制add_library( # Sets the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
native-lib.cpp
)OpenSL ES 录制 PCM 音频数据流程主要有如下：
1、 新建native-lib.cpp文件，然后引入头文件
代码语言：txt复制#include <SLES/OpenSLES.h>
#include <SLES/OpenSLES_Android.h>声明SLObjectItf接口类型的引擎接口对象engineObject，而后用方法slCreateEngine建立一个引擎接口对象；建立好引擎接口对象后，须要用SLObjectItf的Realize方法来实现engineObject；最后用SLObjectItf的GetInterface方法来初始化SLEngnineItf对象实例。如：
代码语言：txt复制//引擎接口
static SLObjectItf engineObject = NULL;
//引擎对象
static SLEngineItf engineEngine;
void createEngine()
{
SLresult result;
result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL);
result = (*engineObject)->Realize(engineObject, SL_BOOLEAN_FALSE);
result = (*engineObject)->GetInterface(engineObject, SL_IID_ENGINE, &engineEngine);
}2、设置IO设备麦克风，设置buffer队列，设置录制规格。
代码语言：txt复制 /**
* 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};3、创建录音器
代码语言：txt复制 /**
* 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);4、设置回调函数
代码语言：txt复制 result = (*recorderBufferQueue)->RegisterCallback(recorderBufferQueue, bqRecorderCallback, NULL);
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
fwrite(recordBuffer->getNowBuffer(), 1, recorderSize, inputPcmFile);
if(finished)
{
(*recorderRecord)->SetRecordState(recorderRecord, SL_RECORDSTATE_STOPPED);
fclose(inputPcmFile);
} else{
(*recorderBufferQueue)->Enqueue(recorderBufferQueue, recordBuffer->getRecordBuffer(),
recorderSize);
}
}5、开始录音
代码语言：txt复制 /**
* 开始录音
*/
(*recorderRecord)->SetRecordState(recorderRecord, SL_RECORDSTATE_RECORDING);小结
通过上面五个步骤就完成了Android OpenGL ES录制pcm功能，文章最后会附送上demo链接，demo生成的pcm数据会保存在
/Android/data/com.pengjie0668.opensles.demo/cache/temp.pcm
github demo下载链接
