我正在使用RemoteIO音頻單元用於在我的應用中使用kAudioUnitProperty_ScheduledFileIDs
進行音頻播放。 音頻文件格式爲PCM格式。我如何爲這種情況實現渲染回調函數,以便我可以手動修改緩衝區樣本?
這裏是我的代碼:
核心音頻:文件播放呈現回調函數
static AudioComponentInstance audioUnit;
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
AudioComponent comp = AudioComponentFindNext(NULL, &desc);
CheckError(AudioComponentInstanceNew(comp, &audioUnit), "error AudioComponentInstanceNew");
NSURL *playerFile = [[NSBundle mainBundle] URLForResource:@"short" withExtension:@"wav"];
AudioFileID audioFileID;
CheckError(AudioFileOpenURL((__bridge CFURLRef)playerFile, kAudioFileReadPermission, 0, &audioFileID), "error AudioFileOpenURL");
// Determine file properties
UInt64 packetCount;
UInt32 size = sizeof(packetCount);
CheckError(AudioFileGetProperty(audioFileID, kAudioFilePropertyAudioDataPacketCount, &size, &packetCount),
"AudioFileGetProperty(kAudioFilePropertyAudioDataPacketCount)");
AudioStreamBasicDescription dataFormat;
size = sizeof(dataFormat);
CheckError(AudioFileGetProperty(audioFileID, kAudioFilePropertyDataFormat, &size, &dataFormat),
"AudioFileGetProperty(kAudioFilePropertyDataFormat)");
// Assign the region to play
ScheduledAudioFileRegion region;
memset (®ion.mTimeStamp, 0, sizeof(region.mTimeStamp));
region.mTimeStamp.mFlags = kAudioTimeStampSampleTimeValid;
region.mTimeStamp.mSampleTime = 0;
region.mCompletionProc = NULL;
region.mCompletionProcUserData = NULL;
region.mAudioFile = audioFileID;
region.mLoopCount = 0;
region.mStartFrame = 0;
region.mFramesToPlay = (UInt32)packetCount * dataFormat.mFramesPerPacket;
CheckError(AudioUnitSetProperty(audioUnit, kAudioUnitProperty_ScheduledFileRegion, kAudioUnitScope_Global, 0, ®ion, sizeof(region)),
"AudioUnitSetProperty(kAudioUnitProperty_ScheduledFileRegion)");
// Prime the player by reading some frames from disk
UInt32 defaultNumberOfFrames = 0;
CheckError(AudioUnitSetProperty(audioUnit, kAudioUnitProperty_ScheduledFilePrime, kAudioUnitScope_Global, 0, &defaultNumberOfFrames, sizeof(defaultNumberOfFrames)),
"AudioUnitSetProperty(kAudioUnitProperty_ScheduledFilePrime)");
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = MyCallback;
callbackStruct.inputProcRefCon = (__bridge void * _Nullable)(self);
CheckError(AudioUnitSetProperty(audioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, &callbackStruct, sizeof(callbackStruct)), "error AudioUnitSetProperty[kAudioUnitProperty_setRenderCallback]");
CheckError(AudioUnitInitialize(audioUnit), "error AudioUnitInitialize");
回調函數:
static OSStatus MyCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData){
printf("my callback");
return noErr;
}
按下按鈕音頻單元開始播放:
- (IBAction)playSound:(id)sender {
CheckError(AudioOutputUnitStart(audioUnit), "error AudioOutputUnitStart");
}
這代碼在編譯期間失敗kAudioUnitErr_InvalidProperty(-10879)錯誤。目標是修改已從AudioFileID中讀取的緩衝樣本,並將結果發送給發言人。
'MyCallback()'在哪裏? – user3078414
@ user3078414,添加到'UPD:' – jangofett
部分'kAudioUnitErr_InvalidElement'又名'-10877'似乎是一個初始化錯誤,不是一個運行時錯誤AFAIK。我不明白你說的「其他代碼工作正常」是什麼意思。你的程序的「結構」是什麼?你說「使用AudioUnits」。這是一個單一的AU程序,還是使用_multiple AU?做什麼的?如果是這樣,你明確地連接它們還是使用'AUGraph' API? – user3078414