Stop AUGraph's stuttering - ios

Question

I am receiving a stuttered sound when I first start the AUGraph and play a song with a kAudioUnitSubType_AudioFilePlayer component. The stutter is about 3 seconds but its enough to bother me plus I notice that music stops for a split second sometimes while playing(I guess to buffer?). I have tried changing the kAudioUnitProperty_ScheduledFilePrime to random values but notice no change.
What variables or values should I be looking to change to get rid of this flaw? Is this an issue with the stream format?
I am using the YBAudioUnit from https://github.com/ronaldmannak/YBAudioFramework/tree/master/YBAudioUnit
Code:
YBAudioFilePlayer:
- (void)setFileURL:(NSURL *)fileURL typeHint:(AudioFileTypeID)typeHint {
if (_fileURL) {
// Release old file:
AudioFileClose(_audioFileID);
}
_fileURL = fileURL;
if (_fileURL) {
YBAudioThrowIfErr(AudioFileOpenURL((__bridge CFURLRef)fileURL, kAudioFileReadPermission, typeHint, &_audioFileID));
YBAudioThrowIfErr(AudioUnitSetProperty(_auAudioUnit, kAudioUnitProperty_ScheduledFileIDs, kAudioUnitScope_Global, 0, &_audioFileID, sizeof(AudioFileID)));
// Get number of audio packets in the file:
UInt32 propsize = sizeof(_filePacketsCount);
YBAudioThrowIfErr(AudioFileGetProperty(_audioFileID, kAudioFilePropertyAudioDataPacketCount, &propsize, &_filePacketsCount));
// Get file's asbd:
propsize = sizeof(_fileASBD);
YBAudioThrowIfErr(AudioFileGetProperty(_audioFileID, kAudioFilePropertyDataFormat, &propsize, &_fileASBD));
// Get unit's asbd:
propsize = sizeof(_fileASBD);
AudioUnitGetProperty(_auAudioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &_unitASBD, &propsize);
if (_fileASBD.mSampleRate > 0 && _unitASBD.mSampleRate > 0) {
_sampleRateRatio = _unitASBD.mSampleRate / _fileASBD.mSampleRate;
} else {
_sampleRateRatio = 1.;
}
}
}
To play I call these methods on the YBAudioFilePlayer:
[player1 setFileURL:item.url typeHint:0];
[player1 scheduleEntireFilePrimeAndStartImmediately];
[graph start];//On a YBAudioUnitGraph which is really just a basic AUGraph

Answer 1

More than an answer this is a comment, but it's rather large, so I'll post it here.
I don't have the time and patience to study the code inside the YB.. API. But a couple of thigns come to my mind.
First I remember experimenting with Audio Units (using Apple's API) and I had a lot of stuttering going on. I solved the problem removing all objective-C calls inside the callback that feeds data to my AUGraph (well, I removed all except one that I couldn't get rid of). I replaced all Objective-c calls with pure C and C++ calls. Example:
... this is the render callback
int i = [myClass someProperty]; // obj-c
int i = myClass->someVarialbe; // c, c++
This was just an example, but it improved dramatically and I got rid of stuttering. Maybe you can take a look at the implementation of the YBXX API and see if there are a lot of obj-c calls in the callback, and if there are, I would not use the API.
Second observation. It seems that you're only trying to play an audio file, for which having an AudioGraph is a lot of overhead, you could use a single IO Audio Unit without the Graph.

Answer 2

There are a large number of questions to ask:
First, are you using a compressed audio file? If so, you may need to take into account padding frames (kAudioFilePropertyPacketTableInfo) to get the real number of audio frames in the file. Perhaps try an AIFF, CAF, or WAV file.
Have you made sure no other audio app are running in the background?
Are there any logging messages?
Have you tried posting to their issue page on github?
The final question is why you are trying to use their framework (which hasn't been updated in two years). I would recommend The Amazing Audio Engine. It is actively developed by some of the best audio folks on iOS.