Android audio and video goes deep into thirteen OpenSL ES to create a music player, which can pause and adjust the volume (with source code download), androidopensl

Android audio and video goes deep into thirteen OpenSL ES to create a music player, which can pause and adjust the volume (with source code download), androidopensl

Project address
Https://github.com/979451341/OpenSLAudio

OpenSL ES is a public audio API developed based on NDK, that is, the underlying C language. It can be used to achieve standardized, high-performance, and low-response-time audio functions.

This is a music player using OpenSL ES. It can play m4a and mp3 files, pause and adjust the volume.

Some steps are required to play music.

1. Create a sound engine

First, create an object interface for the sound engine.
Result = slCreateEngine (& engineObject, 0, NULL, 0, NULL, NULL );

Then implement it
Result = (* engineObject)-> Realize (engineObject, SL_BOOLEAN_FALSE );

Capture sound engine objects
Result = (* engineObject)-> GetInterface (engineObject, SL_IID_ENGINE, & engineEngine );

Create "output mixer"
Result = (* engineEngine)-> CreateOutputMix (engineEngine, & outputMixObject, 1, ids, req );

Achieve output of mixed audio
Result = (* outputMixObject)-> Realize (outputMixObject, SL_BOOLEAN_FALSE );

 

2. Create a sound player

Create and implement a player

    // 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;

 

3. Set the playback buffer.

Data format Configuration

    SLDataFormat_PCM format_pcm = {SL_DATAFORMAT_PCM, 1, SL_SAMPLINGRATE_8,                                   SL_PCMSAMPLEFORMAT_FIXED_16, SL_PCMSAMPLEFORMAT_FIXED_16,                                   SL_SPEAKER_FRONT_CENTER, SL_BYTEORDER_LITTLEENDIAN};

The data locator is used to locate the storage location of audio data to be played. It can be divided into four types: memory location, input/output device location, Buffer Queue location, and midi Buffer Queue location.

Data locator Configuration

    SLDataLocator_AndroidSimpleBufferQueue loc_bufq = {SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, 2};

 

Get the cache queue interface and register

    // get the buffer queue interface    result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_BUFFERQUEUE,                                             &bqPlayerBufferQueue);    assert(SL_RESULT_SUCCESS == result);    (void)result;    // register callback on the buffer queue    result = (*bqPlayerBufferQueue)->RegisterCallback(bqPlayerBufferQueue, bqPlayerCallback, NULL);    assert(SL_RESULT_SUCCESS == result);    (void)result;

4. obtain other interfaces to control playback.

 

Interface for obtaining sound effects

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

Obtain the volume Interface

    // 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;

5. Provide playback data

Open a music file

    // convert Java string to UTF-8    const char *utf8 = (*env)->GetStringUTFChars(env, filename, NULL);    assert(NULL != utf8);    // use asset manager to open asset by filename    AAssetManager* mgr = AAssetManager_fromJava(env, assetManager);    assert(NULL != mgr);    AAsset* asset = AAssetManager_open(mgr, utf8, AASSET_MODE_UNKNOWN);    // release the Java string and UTF-8    (*env)->ReleaseStringUTFChars(env, filename, utf8);    // the asset might not be found    if (NULL == asset) {        return JNI_FALSE;    }    // open asset as file descriptor    off_t start, length;    int fd = AAsset_openFileDescriptor(asset, &start, &length);    assert(0 <= fd);    AAsset_close(asset);

Set playback data

    SLDataLocator_AndroidFD loc_fd = {SL_DATALOCATOR_ANDROIDFD, fd, start, length};    SLDataFormat_MIME format_mime = {SL_DATAFORMAT_MIME, NULL, SL_CONTAINERTYPE_UNSPECIFIED};    SLDataSource audioSrc = {&loc_fd, &format_mime};

6. Play Music

You only need to change the playing status of a music player through the playing interface. Pause is also done, and stop is also done, but the pause must be done by the previous playing cache; otherwise, the pause is equivalent to stopping.

        result = (*fdPlayerPlay)->SetPlayState(fdPlayerPlay, isPlaying ?                                                             SL_PLAYSTATE_PLAYING : SL_PLAYSTATE_PAUSED);

 

7. Mediation volume

SLVolumeItf getVolume(){    if (fdPlayerVolume != NULL)        return fdPlayerVolume;    else        return bqPlayerVolume;}void Java_com_ywl5320_openslaudio_MainActivity_setVolumeAudioPlayer(JNIEnv* env, jclass clazz,                                                                      jint millibel){    SLresult result;    SLVolumeItf volumeItf = getVolume();    if (NULL != volumeItf) {        result = (*volumeItf)->SetVolumeLevel(volumeItf, millibel);        assert(SL_RESULT_SUCCESS == result);        (void)result;    }}

8. release resources

When the app is disabled, the occupied resources are released.

void Java_com_ywl5320_openslaudio_MainActivity_shutdown(JNIEnv* env, jclass clazz){    // destroy buffer queue audio player object, and invalidate all associated interfaces    if (bqPlayerObject != NULL) {        (*bqPlayerObject)->Destroy(bqPlayerObject);        bqPlayerObject = NULL;        bqPlayerPlay = NULL;        bqPlayerBufferQueue = NULL;        bqPlayerEffectSend = NULL;        bqPlayerMuteSolo = NULL;        bqPlayerVolume = NULL;    }    // destroy file descriptor audio player object, and invalidate all associated interfaces    if (fdPlayerObject != NULL) {        (*fdPlayerObject)->Destroy(fdPlayerObject);        fdPlayerObject = NULL;        fdPlayerPlay = NULL;        fdPlayerSeek = NULL;        fdPlayerMuteSolo = NULL;        fdPlayerVolume = NULL;    }    // destroy output mix object, and invalidate all associated interfaces    if (outputMixObject != NULL) {        (*outputMixObject)->Destroy(outputMixObject);        outputMixObject = NULL;        outputMixEnvironmentalReverb = NULL;    }    // destroy engine object, and invalidate all associated interfaces    if (engineObject != NULL) {        (*engineObject)->Destroy(engineObject);        engineObject = NULL;        engineEngine = NULL;    }}

References
Http://blog.csdn.net/u013898698/article/details/72822595

Http://blog.csdn.net/ywl5320/article/details/78503768