概述
我們?nèi)粘Ｔ谔幚硪纛l錄制的時候，大部分情況下都是使用AudioRecord錄制原始的PCM數(shù)據(jù)，但是音頻相關的處理通常都是在native層進行的，今天筆者要記錄一下在native層通過OpenSL ES來完成音頻的錄制。
配置權限
動態(tài)權限的申請這里不贅述
<uses-permission android:name="android.permission.RECORD_AUDIO"/>
導入OpenSL ES庫
CMake方式：CMakeList.txt中加入
target_link_libraries(native-lib OpenSLES)
NDK Build方式：在Android.mk文件添加選項
LOCAL_LDLIBS = -lOpenSLES
源代碼中引入頭文件
#include <SLES/OpenSLES.h>
#include <SLES/OpenSLES_Android.h>
錄制流程分析
image
開始錄制
SL_API SLresult SLAPIENTRY slCreateEngine(
SLObjectItf *pEngine, //對象地址，用于傳出對象
SLuint32 numOptions, //配置參數(shù)數(shù)量
const SLEngineOption *pEngineOptions, //配置參數(shù)，為枚舉數(shù)組
SLuint32 numInterfaces, //支持的接口數(shù)量
const SLInterfaceID *pInterfaceIds, //具體的要支持的接口，是枚舉的數(shù)組
const SLboolean *pInterfaceRequired //具體的要支持的接口是開放的還是關閉的，也是一個數(shù)組，這三個參數(shù)長度是一致的
);
void OpenSLESRecorder::StartRecord(const char *pcmPath, int sampleRate, int channels, int bitRate) {
//打開輸出文件
pcmFile = fopen(pcmPath, "w");
recordBuffer = new RecordBuffer(RECORDER_FRAMES * 2);
//1. 調(diào)用全局方法創(chuàng)建一個引擎對象(OpenSL ES唯一入口)
SLresult result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL);
if (SL_RESULT_SUCCESS != result) {
return;
}
//2. 實例化這個對象
result = (*engineObject)->Realize(engineObject, SL_BOOLEAN_FALSE);
if (SL_RESULT_SUCCESS != result) {
return;
}
//3. 從這個對象里面獲取引擎接口
result = (*engineObject)->GetInterface(engineObject, SL_IID_ENGINE, &engineEngine);
if (SL_RESULT_SUCCESS != result) {
return;
}
//4. 設置IO設備(麥克風)
SLDataLocator_IODevice ioDevice = {
SL_DATALOCATOR_IODEVICE, //類型
SL_IODEVICE_AUDIOINPUT, //device類型 選擇了音頻輸入類型
SL_DEFAULTDEVICEID_AUDIOINPUT, //deviceID
NULL //device實例
};
SLDataSource dataSource = {
&ioDevice, //SLDataLocator_IODevice配置輸入
NULL //輸入格式,采集的并不需要
};
//5. 設置輸出buffer隊列
SLDataLocator_AndroidSimpleBufferQueue buffer_queue = {
SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, //類型 這里只能是這個常量
2 //buffer的數(shù)量
};
//6. 設置輸出數(shù)據(jù)的格式
SLDataFormat_PCM pcmFormat = {
SL_DATAFORMAT_PCM, //輸出PCM格式的數(shù)據(jù)
(SLuint32) channels, //輸出的聲道數(shù)量
SL_SAMPLINGRATE_44_1, //輸出的采樣頻率，這里是44100Hz
SL_PCMSAMPLEFORMAT_FIXED_16, //輸出的采樣格式，這里是16bit
SL_PCMSAMPLEFORMAT_FIXED_16, //一般來說，跟隨上一個參數(shù)
SL_SPEAKER_FRONT_LEFT |
SL_SPEAKER_FRONT_RIGHT, //雙聲道配置，如果單聲道可以用 SL_SPEAKER_FRONT_CENTER
SL_BYTEORDER_LITTLEENDIAN //PCM數(shù)據(jù)的大小端排列
};
SLDataSink audioSink = {
&buffer_queue, //SLDataFormat_PCM配置輸出
&pcmFormat //輸出數(shù)據(jù)格式
};
SLAndroidSimpleBufferQueueItf recorderBufferQueue; //Buffer接口
//7. 創(chuàng)建錄制的對象
const SLInterfaceID id[1] = {SL_IID_ANDROIDSIMPLEBUFFERQUEUE};
const SLboolean req[1] = {SL_BOOLEAN_TRUE};
result = (*engineEngine)->CreateAudioRecorder(engineEngine, //引擎接口
&recorderObject, //錄制對象地址，用于傳出對象
&dataSource, //輸入配置
&audioSink, //輸出配置
1, //支持的接口數(shù)量
id, //具體的要支持的接口
req //具體的要支持的接口是開放的還是關閉的
);
if (SL_RESULT_SUCCESS != result) {
return;
}
//8. 實例化這個錄制對象
result = (*recorderObject)->Realize(recorderObject, SL_BOOLEAN_FALSE);
if (SL_RESULT_SUCCESS != result) {
return;
}
//9. 獲取錄制接口
(*recorderObject)->GetInterface(recorderObject, SL_IID_RECORD, &recorderRecorder);
//10. 獲取Buffer接口
(*recorderObject)->GetInterface(recorderObject, SL_IID_ANDROIDSIMPLEBUFFERQUEUE,
&recorderBufferQueue);
finished = false;
result = (*recorderBufferQueue)->Enqueue(recorderBufferQueue, recordBuffer->getRecordBuffer(),
recorderSize);
if (SL_RESULT_SUCCESS != result) {
return;
}
result = (*recorderBufferQueue)->RegisterCallback(recorderBufferQueue, RecordCallback,
this);
if (SL_RESULT_SUCCESS != result) {
return;
}
//11. 開始錄音
(*recorderRecorder)->SetRecordState(recorderRecorder, SL_RECORDSTATE_RECORDING);
}
停止錄制
void OpenSLESRecorder::StopRecord() {
if (NULL != recorderRecorder) {
finished = true;
}
}
回調(diào)函數(shù)
static void RecordCallback(SLAndroidSimpleBufferQueueItf bufferQueue, void *context) {
LOGI("錄制大小: %d", recorderSize);
OpenSLESRecorder *recorder = (OpenSLESRecorder *) context;
if (NULL != recorder->recordBuffer) {
fwrite(recorder->recordBuffer->getNowBuffer(), 1, recorderSize, recorder->pcmFile);
}
if (recorder->finished) {
(*recorder->recorderRecorder)->SetRecordState(recorder->recorderRecorder,
SL_RECORDSTATE_STOPPED);
//刷新緩沖區(qū)后，關閉流
fclose(recorder->pcmFile);
//釋放內(nèi)存
delete recorder->recordBuffer;
recorder->recordBuffer = NULL;
LOGI("停止錄音");
} else {
(*bufferQueue)->Enqueue(bufferQueue, recorder->recordBuffer->getRecordBuffer(),
recorderSize);
}
}
小結
如果參考官方的例子，整個過程并不算復雜，筆者也是參考官方的例子進行操作實踐
image
項目地址：audio-opensles
https://github.com/byhook/ffmpeg4android
參考
https://github.com/googlesamples/android-ndk/tree/master/native-audio
https://developer.android.com/ndk/guides/audio/opensl/getting-started
