Android 音频 OpenSL ES PCM数据播放

        PCM 数据播放在开发中也经常使用，例如自己编写播放器，解码之后的音频PCM数据，就可以通过OpenSL 播放，比用Java层的AudioTrack更快，延迟更低。

        下面我们编写OpenSL PCM播放，播放的主要逻辑是从文件读取PCM数据然后播放，代码编写环境Eclipse。

一、 Eclipse 创建Android工程

二、布局XML 创建文件 /res/layout/activity_audio_track.xml

布局文件就一个播放按钮

三、Activity类  创建/src/com/example/testopensl/AudioTrackActivity.java

package com.example.testopensl;

import com.example.audio.R;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;

public class AudioTrackActivity extends Activity implements OnClickListener {

	private static String URI_PCM = "/mnt/sdcard/pm.pcm";

	static {
		System.loadLibrary("TestAudio");
	}

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_audio_track);
		findViewById(R.id.btn_play).setOnClickListener(this);
		createEngine();

	}

	@Override
	public void onClick(View v) {
		switch (v.getId()) {
		case R.id.btn_play:
			createAudioPlayer(URI_PCM);
			break;
		}
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		shutdown();
	}

	/** Native methods, implemented in jni folder */
	public static native void createEngine();

	public static native boolean createAudioPlayer(String uri);

	public static native void setPlayingAudioPlayer(boolean isPlaying);

	public static native void setVolumeAudioPlayer(int millibel);

	public static native void setMutAudioPlayer(boolean mute);

	public static native void shutdown();
}

四、编写日志头文件，用于日志输出， 创建/jni/log.h 文件

#ifndef LOG_H_
#define LOG_H_

#include 

#ifndef DGB
#define DGB 0
#endif

#ifndef LOG_TAG
#define LOG_TAG __FILE__
#endif

#ifndef ALOGD
#if DGB
#define ALOGD(...) \
		__android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#else
#define ALOGD(...)   ((void)0)
#endif
#endif

#endif /* LOG_H_ */

五、用javah命令 生成jni 头文件. 文件目录/jni/com_example_testopensl_AudioTrackActivity.h

/* DO NOT EDIT THIS FILE - it is machine generated */
#include 
/* Header for class com_example_testopensl_AudioTrackActivity */

#ifndef _Included_com_example_testopensl_AudioTrackActivity
#define _Included_com_example_testopensl_AudioTrackActivity
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    createEngine
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_createEngine
  (JNIEnv *, jclass);

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    createAudioPlayer
 * Signature: (Ljava/lang/String;)Z
 */
JNIEXPORT jboolean JNICALL Java_com_example_testopensl_AudioTrackActivity_createAudioPlayer
  (JNIEnv *, jclass, jstring);

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    setPlayingAudioPlayer
 * Signature: (Z)V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_setPlayingAudioPlayer
  (JNIEnv *, jclass, jboolean);

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    setVolumeAudioPlayer
 * Signature: (I)V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_setVolumeAudioPlayer
  (JNIEnv *, jclass, jint);

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    setMutAudioPlayer
 * Signature: (Z)V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_setMutAudioPlayer
  (JNIEnv *, jclass, jboolean);

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    shutdown
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_shutdown
  (JNIEnv *, jclass);

#ifdef __cplusplus
}
#endif
#endif

六、JNI的实现 /jni/com_example_testopensl_AudioTrackActivity.cpp

/** log */
#define LOG_TAG "AudioTrackActivity"
#define DGB 1

#include "log.h"
#include 
#include 
#include 
#include 
#include 

#include "com_example_testopensl_AudioTrackActivity.h"

class PlaybackThread;

// engine interfaces
static SLObjectItf engineObject = NULL;
static SLEngineItf engineEngine;

// output mix interfaces
static SLObjectItf outputMixObject = NULL;

// buffer queue player interfaces
static SLObjectItf bqPlayerObject = NULL;
static SLPlayItf bqPlayerPlay;
static SLAndroidSimpleBufferQueueItf bqPlayerBufferQueue;
static SLEffectSendItf bqPlayerEffectSend;
static SLVolumeItf bqPlayerVolume;
static PlaybackThread* mThread;

class PlaybackThread {
private:
	FILE *mFile;
	void* mBuffer;
	size_t mSize;
	bool read;
public:
	PlaybackThread(const char* uri) :
			mFile(NULL), mBuffer(NULL), mSize(0), read(true) {
		mFile = fopen((char*) uri, "r");
		if (mFile == NULL) {
			ALOGD("open file error %s", uri);
			return;
		}
		mBuffer = malloc(8192);
	}

	void start() {
		if (mFile == NULL) {
			return;
		}
		enqueueBuffer();
	}

	// release file buffer
	void release() {
		if (mFile != NULL) {
			fclose(mFile);
			mFile == NULL;
		}
		if (mBuffer != NULL) {
			free(mBuffer);
			mBuffer == NULL;
		}
	}

	~PlaybackThread() {
		release();
		ALOGD("~PlaybackThread");
	}

	void enqueueBuffer() {
		if (bqPlayerBufferQueue == NULL) {
			return;
		}
		// for streaming playback, replace this test by logic to find and fill the next buffer
		while (true) {
			if (read) {
				mSize = fread(mBuffer, 1, 8192, mFile);
			}
			if (mSize > 0) {
				SLresult result;
				// enqueue another buffer
				result = (*bqPlayerBufferQueue)->Enqueue(bqPlayerBufferQueue, mBuffer, mSize);
				if (result == SL_RESULT_BUFFER_INSUFFICIENT) {
					read = false;
					return;
				}
				read = true;
			} else {
				return;
			}
		}
 	}

	// this callback handler is called every time a buffer finishes playing
	static void playerCallback(SLAndroidSimpleBufferQueueItf bq, void *context) {
		assert(NULL != context);

		PlaybackThread* thread = (PlaybackThread *) context;
		if (thread != NULL) {
			thread->enqueueBuffer();
		}
	}
};

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    createEngine
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_createEngine(JNIEnv *, jclass) {
	SLresult result;

	// create engine
	result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// realize the engine
	result = (*engineObject)->Realize(engineObject, SL_BOOLEAN_FALSE);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// get the engine interface, which is needed in order to create other objects
	result = (*engineObject)->GetInterface(engineObject, SL_IID_ENGINE, &engineEngine);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// create output mix,
	result = (*engineEngine)->CreateOutputMix(engineEngine, &outputMixObject, 0, 0, 0);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// realize the output mix
	result = (*outputMixObject)->Realize(outputMixObject, SL_BOOLEAN_FALSE);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;
}

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    createAudioPlayer
 * Signature: (Ljava/lang/String;)Z
 */
JNIEXPORT jboolean JNICALL Java_com_example_testopensl_AudioTrackActivity_createAudioPlayer(JNIEnv *env, jclass clazz, jstring uri) {

	const char* utf8Uri = env->GetStringUTFChars(uri, NULL);

	SLresult result;
	// configure audio source
	SLDataLocator_AndroidSimpleBufferQueue loc_bufq = { SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, 3 };
	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 };
	SLDataSource audioSrc = { &loc_bufq, &format_pcm };

	// configure audio sink
	SLDataLocator_OutputMix loc_outmix = { SL_DATALOCATOR_OUTPUTMIX, outputMixObject };
	SLDataSink audioSnk = { &loc_outmix, NULL };

	// create audio player
	const SLInterfaceID ids[3] = { SL_IID_BUFFERQUEUE, SL_IID_EFFECTSEND, SL_IID_VOLUME };
	const SLboolean req[3] = { SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE };
	result = (*engineEngine)->CreateAudioPlayer(engineEngine, &bqPlayerObject, &audioSrc, &audioSnk, 3, ids, req);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// realize the player
	result = (*bqPlayerObject)->Realize(bqPlayerObject, SL_BOOLEAN_FALSE);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// get the play interface
	result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_PLAY, &bqPlayerPlay);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// get the buffer queue interface
	result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_BUFFERQUEUE, &bqPlayerBufferQueue);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	mThread = new PlaybackThread(utf8Uri);
	// register callback on the buffer queue
	result = (*bqPlayerBufferQueue)->RegisterCallback(bqPlayerBufferQueue, PlaybackThread::playerCallback, mThread);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// get the effect send interface
	result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_EFFECTSEND, &bqPlayerEffectSend);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// get the volume interface
	result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_VOLUME, &bqPlayerVolume);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;

	// set the player's state to playing
	result = (*bqPlayerPlay)->SetPlayState(bqPlayerPlay, SL_PLAYSTATE_PLAYING);
	assert(SL_RESULT_SUCCESS == result);
	(void) result;
	//pthread_t id;

	mThread->start();
	env->ReleaseStringUTFChars(uri, utf8Uri);
	ALOGD("createAudioPlayer finish");
	return 0;
}

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    setPlayingAudioPlayer
 * Signature: (Z)V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_setPlayingAudioPlayer(JNIEnv *, jclass, jboolean) {

}

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    setVolumeAudioPlayer
 * Signature: (I)V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_setVolumeAudioPlayer(JNIEnv *, jclass, jint) {

}

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    setMutAudioPlayer
 * Signature: (Z)V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_setMutAudioPlayer(JNIEnv *, jclass, jboolean) {

}

/*
 * Class:     com_example_testopensl_AudioTrackActivity
 * Method:    shutdown
 * Signature: ()V
 */
JNIEXPORT void JNICALL Java_com_example_testopensl_AudioTrackActivity_shutdown(JNIEnv *, jclass) {

	//destory player object
	if (bqPlayerObject != NULL) {
		(*bqPlayerObject)->Destroy(bqPlayerObject);
		bqPlayerPlay = NULL;
		bqPlayerBufferQueue = NULL;
		bqPlayerEffectSend = NULL;
		bqPlayerVolume = NULL;
	}

	// destroy output mix object, and invalidate all associated interfaces
	if (outputMixObject != NULL) {
		(*outputMixObject)->Destroy(outputMixObject);
		outputMixObject = NULL;
	}

	// destroy engine object, and invalidate all associated interfaces
	if (engineObject != NULL) {
		(*engineObject)->Destroy(engineObject);
		engineObject = NULL;
		engineEngine = NULL;
	}

	if (mThread != NULL) {
		delete mThread;
		mThread = NULL;
	}
}

方法说明：

        Java_com_example_testopensl_AudioTrackActivity_createEngine 创建引擎
        Java_com_example_testopensl_AudioTrackActivity_createAudioPlayer 创建播放器并开始播放
        Java_com_example_testopensl_AudioTrackActivity_shutdown 释放资源
        Java_com_example_testopensl_AudioTrackActivity_setPlayingAudioPlayer 未实现
        Java_com_example_testopensl_AudioTrackActivity_setVolumeAudioPlayer 未实现
        Java_com_example_testopensl_AudioTrackActivity_setMutAudioPlayer 未实现
未实现方法可以参考 URI播放实现

七、创建/jni/Android.mk 编译文件

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := TestAudio
LOCAL_SRC_FILES := com_example_testopensl_AudioTrackActivity.cpp
LOCAL_LDLIBS += -llog -lOpenSLES -landroid

include $(BUILD_SHARED_LIBRARY)

LOCAL_LDLIBS 需要加llog、lOpenSLES、landroid 编译链接库

八、AndroidManifest 配置

编写完Eclipse 结构图如下：

运行之后界面图如下：

代码中使用的PCM数据信息：

        采样率：44100

        声道：2

        编码：16BIT

关键代码是在 com_example_testopensl_AudioTrackActivity.cpp 中创建播放器AudioSrc 参数

	// configure audio source
	SLDataLocator_AndroidSimpleBufferQueue loc_bufq = { SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, 3 };
	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 };
	SLDataSource audioSrc = { &loc_bufq, &format_pcm };

上面指定了播放PCM数据的信息

代码编写完，功能比较简单，点击播放按钮从文件读取PCM数据。