OpenSL ES(Open Sound Library for Embedded Systems)
网上解释OpenSL ES是跨平台、针对嵌入式系统精心优化的硬件音频加速API。它为嵌入式移动多媒体设备上的本地应用程序开发者提供标准化, 高性能,低响应时间的音频功能实现方法，并实现软/硬件音频性能的直接跨平台部署，降低执行难度，促进高级音频市场的发展。
NDK开发OpenSL ES跨平台高效音频解决方案.png
接下来直接上代码，注释都在代码中，具体的开发步骤可以参考
03.Eclipse下Ndk开发（以文件加密为例模拟一下开发过程）
AudioPlayer.java
package com.example.openslaudio;
public class AudioPlayer {
public native static void play(String filePath);
static{
System.loadLibrary("OpenSLAudioPlayer");
}
}
MainActivity.java
package com.example.openslaudio;
import java.io.File;
import android.Manifest;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void play(View btn){
new Thread(){
public void run() {
File file = new File(Environment.getExternalStorageDirectory(),"text.wav");
AudioPlayer.play(file.getAbsolutePath());
}
}.start();
}
}
通过环境变量的方式引入transcode-1.1.7/avilib需要做一些配置，详见下图，在C/C++ Build中设置NDK_MODULE_PATH（必须是这个名字），这个路径下放置我们要使用的共享库transcode-1.1.7，至于为什么要这样设置，很简单，如果一个库，你好几个项目都要使用，那么没有必要在每个项目中都添加库文件，只要设置环境变量，然后引入即可，NDKROOT设置ndk路径也是同样道理
共享库环境变量设置.png
Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := OpenSLAudioPlayer
LOCAL_SRC_FILES := OpenSLAudioPlayer.cpp
# Use WAVLib static library
LOCAL_STATIC_LIBRARIES += wavlib_static
# Link with OpenSL ES
LOCAL_LDLIBS += -lOpenSLES -llog
include $(BUILD_SHARED_LIBRARY)
# Import WAVLib library module,如果不引入的话，wavlib.h是无法使用的，主要作用
#就是解码，然后交给OpenSE ES去播放
$(call import-module,transcode-1.1.7/avilib)
com_example_openslaudio_AudioPlayer.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_openslaudio_AudioPlayer */
#ifndef _Included_com_example_openslaudio_AudioPlayer
#define _Included_com_example_openslaudio_AudioPlayer
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_example_openslaudio_AudioPlayer
* Method: play
* Signature: (Ljava/lang/String;)V
*/
JNIEXPORT void JNICALL Java_com_example_openslaudio_AudioPlayer_play
(JNIEnv *, jclass, jstring);
#ifdef __cplusplus
}
#endif
#endif
OpenSLAudioPlayer.cpp
#include <jni.h>
#include "com_example_openslaudio_AudioPlayer.h"
#include "CreateBufferQueueAudioPlayer.cpp"
#include <SLES/OpenSLES.h>
#include <SLES/OpenSLES_Android.h>
#include <android/log.h>
extern "C" {
#include "wavlib.h"
}
#define LOGI(FORMAT,...) __android_log_print(ANDROID_LOG_INFO,"renzhenming",FORMAT,##__VA_ARGS__);
#define LOGE(FORMAT,...) __android_log_print(ANDROID_LOG_ERROR,"renzhenming",FORMAT,##__VA_ARGS__);
#define ARRAR_LEN(a) (sizeof(a)/sizeof(a[0]))
//wav文件指针
WAV wav;
//引擎对象
SLObjectItf engineObject;
//引擎接口
SLEngineItf engineInterface;
//混音器
SLObjectItf outputMixObject;
//播放器
SLObjectItf audioPlayerObject;
//缓冲区队列接口
SLAndroidSimpleBufferQueueItf andioPlayerBufferQueueItf;
//播放接口
SLPlayItf audioPlayInterface;
//缓冲区
unsigned char *buffer;
//缓冲区大小
size_t bufferSize;
//打开文件
WAV OpenWaveFile(JNIEnv *env,jstring jinput){
const char* cinput_file = env->GetStringUTFChars(jinput,NULL);
/*typedef enum {
WAV_SUCCESS, no error so far
WAV_NO_MEM, can't acquire requested amount of memory
WAV_IO_ERROR, unable to read/write (often write) data
WAV_BAD_FORMAT, acquired data doesn't seem wav-compliant
WAV_BAD_PARAM, bad parameter for requested operation
WAV_UNSUPPORTED, feature not yet supported by wavlib
} WAVError;*/
WAVError err;
//WAV wav_open(const char *filename, WAVMode mode, WAVError *err);
/**
* typedef enum {
* WAV_READ = 1, open WAV file in read-only mode
* WAV_WRITE = 2, open WAV file in write-only mode
* WAV_PIPE = 4, cut SEEEKs
* } WAVMode;
*/
WAV wav = wav_open(cinput_file,WAV_READ,&err);
LOGI("%d",wav_get_bitrate(wav));
env->ReleaseStringUTFChars(jinput,cinput_file);
if(wav == 0){
//get a human-readable short description of an error code
//Return Value:a pointer to a C-string describing the given error code,
//or NULL if given error code isn't known.
LOGE("%s",wav_strerror(err));
}
return wav;
}
//实例化对象
void RealizeObject(SLObjectItf object){
//非异步（会阻塞线程）
/**
* SLresult (*Realize) (
* SLObjectItf self,
* SLboolean async
* );
*/
(*object)->Realize(object,SL_BOOLEAN_FALSE);
}
//上下文
struct PlayerContext{
WAV wav;
unsigned char *buffer;
size_t bufferSize;
PlayerContext(WAV wav,unsigned char *buffer,size_t bufferSize){
this->wav = wav;
this->buffer = buffer;
this->bufferSize = bufferSize;
}
};
//关闭文件
void CloseWaveFile(WAV wav){
wav_close(wav);
}
//回调函数
/*
* wav_read_data:
* read a buffer of pcm data from given wav file. Delivers data
* in wav-native-byte-order (little endian).
* This function doesn't mess with given data, it just reads
* data verbatim from wav file. so caller must take care to
* split/join channel data or do any needed operation.
*
* Parameters:
* handle: wav handle to write data in
* buffer: pointer to data to store the data readed
* bufsize: size of given buffer.
* Return Value:
* return of bytes effectively readed from wav file.
* -1 means an error.
* Side effects:
* N/A
* Preconditions:
* given wav handle is a valid one obtained as return value of
* wav_open/wav_fdopen; wav handle was opened in WAV_READ mode.
* bufsize is a multiple of 2.
* Postconditions:
* N/A
*
* ssize_t wav_read_data(WAV handle, uint8_t *buffer, size_t bufsize);
*/
void playerCallBack(SLAndroidSimpleBufferQueueItf andioPlayerBufferQueue,void *context){
PlayerContext *ctx = (PlayerContext*)context;
//读取数据
ssize_t readSize = wav_read_data(ctx->wav,ctx->buffer,ctx->bufferSize);
if(readSize > 0){
/**
* SLresult (*Enqueue) (
SLAndroidSimpleBufferQueueItf self,
const void *pBuffer,
SLuint32 size
);
*/
(*andioPlayerBufferQueue)->Enqueue(andioPlayerBufferQueue,ctx->buffer,readSize);
}else{
//destory context中保存的东西
//关闭文件
CloseWaveFile(ctx->wav);
//释放缓存
delete ctx->buffer;
}
}
JNIEXPORT void JNICALL Java_com_example_openslaudio_AudioPlayer_play
(JNIEnv *env, jclass jclazz, jstring input){
//打开文件
WAV wav = OpenWaveFile(env,input);
//创建OpenSL ES引擎，OpenSL ES在Android平台下默认是线程安全的，这样设置是为了兼容其它平台
/**
* SL_API SLresult SLAPIENTRY slCreateEngine(
SLObjectItf *pEngine,
SLuint32 numOptions,
const SLEngineOption *pEngineOptions,
SLuint32 numInterfaces,
const SLInterfaceID *pInterfaceIds,
const SLboolean * pInterfaceRequired
);
*/
SLEngineOption engineOptions[] ={
{(SLuint32)SL_ENGINEOPTION_THREADSAFE,(SLuint32)SL_BOOLEAN_TRUE}
};
slCreateEngine(&engineObject,ARRAR_LEN(engineObject),engineOptions,0,0,0);//没有接口
if(engineObject == NULL){
LOGI("%s","engineObject == NULL");
}else{
LOGI("%s","engineObject != NULL");
}
//实例化对象，对象创建之后，处于未实例化状态，对象虽然存在但未分配任何资源，使用前先实例化（使用完之后destroy）
RealizeObject(engineObject);
//获取引擎接口
/**
* SLresult (*GetInterface) (
SLObjectItf self,
const SLInterfaceID iid,
void * pInterface
);
typedef const struct SLInterfaceID_ {
SLuint32 time_low;
SLuint16 time_mid;
SLuint16 time_hi_and_version;
SLuint16 clock_seq;
SLuint8 node[6];
} * SLInterfaceID;
extern SL_API const SLInterfaceID SL_IID_ENGINE;
*/
(*engineObject)->GetInterface(engineObject,SL_IID_ENGINE,&engineInterface);
//创建输出混音器
/**
* SLresult (*CreateOutputMix) (
SLEngineItf self,
SLObjectItf * pMix,
SLuint32 numInterfaces,
const SLInterfaceID * pInterfaceIds,
const SLboolean * pInterfaceRequired
);
*/
(*engineInterface)->CreateOutputMix(engineInterface,&outputMixObject,0,0,0);//没有接口
//实例化混音器
RealizeObject(outputMixObject);
//创建缓冲区保存读取到的音频数据库
//缓冲区大小 uint8_t wav_get_channels(WAV handle);
bufferSize = wav_get_channels(wav)*wav_get_rate(wav)*wav_get_bits(wav);
buffer = new unsigned char[bufferSize];
//创建带有缓冲区队列的音频播放器
CreateBufferQueueAudioPlayer(wav,engineInterface,outputMixObject,audioPlayerObject);
//实例化音频播放器
RealizeObject(audioPlayerObject);
//获取缓冲区队列接口Buffer Queue Interface
//通过缓冲区接口对缓冲区进行排序播放
/**
* SLresult (*GetInterface) (
SLObjectItf self,
const SLInterfaceID iid,
void * pInterface
);
typedef const struct SLInterfaceID_ {
SLuint32 time_low;
SLuint16 time_mid;
SLuint16 time_hi_and_version;
SLuint16 clock_seq;
SLuint8 node[6];
} * SLInterfaceID;
extern SL_API const SLInterfaceID SL_IID_BUFFERQUEUE;
*/
(*audioPlayerObject)->GetInterface(audioPlayerObject,SL_IID_BUFFERQUEUE,&andioPlayerBufferQueueItf);
//注册音频播放器回调函数
//当播放器完成对前一个缓冲区队列的播放时，回调函数会被调用，然后我们又继续读取音频数据，直到结束
//上下文，包裹参数方便再回调函数中使用
/**
* SLresult (*RegisterCallback) (
SLAndroidSimpleBufferQueueItf self,
slAndroidSimpleBufferQueueCallback callback,
void* pContext
);
*/
PlayerContext *ctx = new PlayerContext(wav,buffer,bufferSize);
(*andioPlayerBufferQueueItf)->RegisterCallback(andioPlayerBufferQueueItf,playerCallBack,ctx);
//获取Play Interface 通过对SetPlayState函数来启动播放音乐
//一旦播放器被置为播放状态。该音频播放器开始等待缓冲区排队就绪
/**
* SLresult (*GetInterface) (
SLObjectItf self,
const SLInterfaceID iid,
void * pInterface
);
*/
(*audioPlayerObject)->GetInterface(audioPlayerObject,SL_IID_PLAY,&audioPlayInterface);
//设置播放状态
/**
* SLresult (*SetPlayState) (
SLPlayItf self,
SLuint32 state
);
*/
(*audioPlayInterface)->SetPlayState(audioPlayInterface,SL_PLAYSTATE_PLAYING);
//开始，让第一个缓冲区入队
playerCallBack(andioPlayerBufferQueueItf,ctx);
}
CreateBufferQueueAudioPlayer.cpp
extern "C" {
#include "wavlib.h"
}
#include <SLES/OpenSLES.h>
#include <SLES/OpenSLES_Android.h>
#include <android/log.h>
#define ARRAY_LEN(a) (sizeof(a) / sizeof(a[0]))
//创建音频播放对象
void CreateBufferQueueAudioPlayer(
WAV wav,
SLEngineItf engineEngine,
SLObjectItf outputMixObject,
SLObjectItf &audioPlayerObject){
// Android针对数据源的简单缓冲区队列定位器
SLDataLocator_AndroidSimpleBufferQueue dataSourceLocator = {
SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, // 定位器类型
1 // 缓冲区数
};
// PCM数据源格式
SLDataFormat_PCM dataSourceFormat = {
SL_DATAFORMAT_PCM, // 格式类型
wav_get_channels(wav), // 通道数
wav_get_rate(wav) * 1000, // 毫赫兹/秒的样本数
wav_get_bits(wav), // 每个样本的位数
wav_get_bits(wav), // 容器大小
SL_SPEAKER_FRONT_CENTER, // 通道屏蔽
SL_BYTEORDER_LITTLEENDIAN // 字节顺序
};
// 数据源是含有PCM格式的简单缓冲区队列
SLDataSource dataSource = {
&dataSourceLocator, // 数据定位器
&dataSourceFormat // 数据格式
};
// 针对数据接收器的输出混合定位器
SLDataLocator_OutputMix dataSinkLocator = {
SL_DATALOCATOR_OUTPUTMIX, // 定位器类型
outputMixObject // 输出混合
};
// 数据定位器是一个输出混合
SLDataSink dataSink = {
&dataSinkLocator, // 定位器
0 // 格式
};
// 需要的接口
SLInterfaceID interfaceIds[] = {
SL_IID_BUFFERQUEUE
};
// 需要的接口，如果所需要的接口不要用，请求将失败
SLboolean requiredInterfaces[] = {
SL_BOOLEAN_TRUE // for SL_IID_BUFFERQUEUE
};
// 创建音频播放器对象
SLresult result = (*engineEngine)->CreateAudioPlayer(
engineEngine,
&audioPlayerObject,
&dataSource,
&dataSink,
ARRAY_LEN(interfaceIds),
interfaceIds,
requiredInterfaces);
}
权限
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
