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Android OpenSL 不支持 SL_IID_PLAYBACKRATE?

转载 作者:行者123 更新时间:2023-11-29 21:19:07 26 4
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我使用 NDK 创建了一个音频乐器,为了获得低延迟性能,我选择 OpenSL 来播放音乐文件。但我未能更改播放音乐的播放速率。这是快照代码:

int OpenSLSoundPool::createOggAudioPlayer(const char *filename, int rate){
SLresult result;
AAsset* asset = AAssetManager_open(mMgr, filename, AASSET_MODE_UNKNOWN);
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);

// configure audio source
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};

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

// create audio player
const SLInterfaceID ids[4] = {SL_IID_SEEK, SL_IID_MUTESOLO, SL_IID_VOLUME, SL_IID_PLAYBACKRATE};
const SLboolean req[4] = {SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE};
result = (*engineEngine)->CreateAudioPlayer(engineEngine, &fdPlayerObject, &audioSrc, &audioSnk,
4, ids, req);
assert(SL_RESULT_SUCCESS == result);
(void)result;

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

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

// get the seek interface
result = (*fdPlayerObject)->GetInterface(fdPlayerObject, SL_IID_SEEK, &fdPlayerSeek);
assert(SL_RESULT_SUCCESS == result);
(void)result;

// get the mute/solo interface
result = (*fdPlayerObject)->GetInterface(fdPlayerObject, SL_IID_MUTESOLO, &fdPlayerMuteSolo);
assert(SL_RESULT_SUCCESS == result);
(void)result;

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

// get playback rate interface
result = (*fdPlayerObject)->GetInterface(fdPlayerObject,
SL_IID_PLAYBACKRATE, &fdPlayerRate);
assert(SL_RESULT_SUCCESS == result);


SLuint32 capa;
result = (*fdPlayerRate)->GetRateRange(fdPlayerRate, 0,
&playbackMinRate, &playbackMaxRate, &playbackRateStepSize, &capa);
assert(SL_RESULT_SUCCESS == result);

result = (*fdPlayerRate)->SetRate(fdPlayerRate, playbackMaxRate);
assert(SL_RESULT_SUCCESS == result);

SLpermille SLrate;
result = (*fdPlayerRate)->GetRate(fdPlayerRate, &SLrate);
assert(SL_RESULT_SUCCESS == result);

// enable whole file looping
result = (*fdPlayerSeek)->SetLoop(fdPlayerSeek, SL_BOOLEAN_FALSE, 0, SL_TIME_UNKNOWN);
assert(SL_RESULT_SUCCESS == result);
(void)result;

return JNI_TRUE;
}

重点是:

result = (*fdPlayerRate)->SetRate(fdPlayerRate, playbackMaxRate);
assert(SL_RESULT_SUCCESS == result);

我尝试在 playbackMaxRate 和 playbackMinRate 之间设置值(在我的 S3 手机上,playbackMaxRate 是 2000,playbackMinRate 是 500)。但是没有效果,android NDK doc说它支持SL_IID_PLAYBACKRATE。我的代码有什么问题吗?非常感谢。

最佳答案

您可以尝试将当前速率属性约束设置为 SL_RATEPROP_PITCHCORAUDIO。默认音频属性为 SL_RATEPROP_NOPITCHCORAUDIO。像这样:

SLuint32 capa;
result = (*fdPlayerRate)->GetRateRange(fdPlayerRate, 0,
&playbackMinRate, &playbackMaxRate, &playbackRateStepSize, &capa);
assert(SL_RESULT_SUCCESS == result);

result = (*fdPlayerRate)->SetPropertyConstraints(fdPlayerRate,
SL_RATEPROP_PITCHCORAUDIO);

if (SL_RESULT_PARAMETER_INVALID == result) {
LOGD("Parameter Invalid");
}
if (SL_RESULT_FEATURE_UNSUPPORTED == result) {
LOGD("Feature Unsupported");
}
if (SL_RESULT_SUCCESS == result) {
assert(SL_RESULT_SUCCESS == result);
LOGD("Success");
}

result = (*fdPlayerRate)->SetRate(fdPlayerRate, playbackMaxRate);
assert(SL_RESULT_SUCCESS == result);

这可能因平台版本和实现而异。它适用于我的 Moto G。希望对您有所帮助。

关于Android OpenSL 不支持 SL_IID_PLAYBACKRATE?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20965559/

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