Android 音频录制-OpenSL ES

Posted 2022-12-07 xyTianZhao

文章目录

• • 什么是 OpenSL ES
  • OpenSL ES 在哪
  • OpenSL ES 录制
  • 相关推荐

android 系统为我们提供了三种录制音频的方式

1. MediaRecord（ Java API）
2. AudioRecord（ Java API）
3. OpenSL ES（ Native API）

上两节说了 MediaRecord 和 AudioRecord，他们都是应用层提供的 Java Api。这节呢就来说下 native 层为我们提供的相关 api。

什么是 OpenSL ES

先来看下 OpenSL ES 官方文档 是怎么介绍的。

This library allows you to use C or C++ to implement high-performance, low-latency audio, whether you are writing a synthesizer, digital audio workstation, karaoke, game, or other real-time app.
The OpenSL ES™ standard exposes audio features similar to those in the MediaPlayer and MediaRecorder APIs in the Android Java framework. OpenSL ES provides a C language interface as well as C++ bindings, allowing you to call the API from code written in either language.

这两段话的大致意思就是。我这个库在音频处理方面老牛逼了，性能高不说，延时还短的不要不要的。而且使用方法和 MediaPlayer 与 MeidaRecord 基本上差别不大，唯一的要求就是得会 C 或者 C艹 呀。

OpenSL ES 在哪

要进行 NDK 开发就必须得先集成相应环境，正如需要 Android SDK 一样。同样需要 Android NDK，如果已经科学上网，则直接在 Android Studio 的 SDk Manager 中直接下载即可

下载完成后新建项目时就会看到有一个 Native C++ 的选项，创建出来的项目是一个 Native 版本的 Hello Word。

OpenSL ES 录制

OpenSL ES 录制音频有如下相关流程

1. 创建接口对象

   void createEngine() 
       SLresult result;
   
       result = slCreateEngine(&engineObj, 0, nullptr, 0, nullptr, nullptr);
       assert(result == SL_RESULT_SUCCESS);
       (void) result;
   
       result = (*engineObj)->Realize(engineObj, SL_BOOLEAN_FALSE);
       assert(SL_RESULT_SUCCESS == result);
       (void) result;
   
       result = (*engineObj)->GetInterface(engineObj, SL_IID_ENGINE, &engine);
       assert(SL_RESULT_SUCCESS == result);
       (void) result;
   
       const SLInterfaceID ids[1] = SL_IID_ENVIRONMENTALREVERB;
       const SLboolean req[1] = SL_BOOLEAN_FALSE;
       // outputMixObj 用于输出声音数据
       (*engine)->CreateOutputMix(engine, &outputMixObj, 1, ids, req);
   
       result = (*outputMixObj)->Realize(outputMixObj, SL_BOOLEAN_FALSE);
       assert(SL_RESULT_SUCCESS == result);
       (void) result;
   
   

2. 创建录音器

   result = (*mAudioEngine->engine)->CreateAudioRecorder(mAudioEngine->engine, &mRecorderObj,
           &audiosrc, &audioSink, 1, id, req);
   if (SL_RESULT_SUCCESS != result) 
       return false;
   
   
   result = (*mRecorderObj)->Realize(mRecorderObj, SL_BOOLEAN_FALSE);
   if (SL_RESULT_SUCCESS != result) 
       return false;
   
   

3. 设置缓冲队列和回调函数

   result = (*mBufferQueue)->RegisterCallback(mBufferQueue, recorderCallback, this);
   

4. 设置录音状态，开始录制

   bool AudioRecorder::start() 
       if (!mIsInitialized) 
           if (!initRecorder()) 
               return false;
           
           mIsInitialized = true;
       
   
       SLresult result;
   
       result = (*mRecorder)->SetRecordState(mRecorder, SL_RECORDSTATE_STOPPED);
       if (SL_RESULT_SUCCESS != result) 
           return false;
       
   
       result = (*mBufferQueue)->Clear(mBufferQueue);
       if (SL_RESULT_SUCCESS != result) 
           return false;
       
   
       // enqueue an empty buffer to be filled by the recorder
       // (for streaming recording, we would enqueue at least 2 empty buffers to start things off)
       result = (*mBufferQueue)->Enqueue(mBufferQueue, mBuffers[mIndex], mBufSize * sizeof(short));
       if (SL_RESULT_SUCCESS != result) 
           return false;
       
   
       // 开始录制
       result = (*mRecorder)->SetRecordState(mRecorder, SL_RECORDSTATE_RECORDING);
       if (SL_RESULT_SUCCESS != result) 
           return false;
       
   
       mIsRecording = true;
       LOGI("start recording...");
   
       return true;
   
   

最后附上 完整源码

相关推荐

音频基础知识

Android 音频录制-MeidaRecord

Android 音频录制-AudioRecord

Android 音频录制-OpenSL ES