Repeating Audio in WatchKit (AVAudioPlayer?)? - watchkit

Question

I am wanting to loop a local audio file in my Apple Watch App. Currently I am using AVAudioPlayerNode and AVAudioEngine which works well but I cannot figure out how to loop the sound.
I noticed that I can use AVAudioPlayer, which has the handy "numberOfLoops" but, for some reason AVAudioPlayer is not working on the watch. I have no idea why.
Here is my current code to play a sound:
_audioPlayer = [[AVAudioPlayerNode alloc] init];
_audioEngine = [[AVAudioEngine alloc] init];
[_audioEngine attachNode:_audioPlayer];
AVAudioFormat *stereoFormat = [[AVAudioFormat alloc] initStandardFormatWithSampleRate:44100 channels:2];
[_audioEngine connect:_audioPlayer to:_audioEngine.mainMixerNode format:stereoFormat];
if (!_audioEngine.isRunning) {
NSError* error;
[_audioEngine startAndReturnError:&error];
}
NSError *error;
NSBundle* appBundle = [NSBundle mainBundle];
NSURL *url = [NSURL fileURLWithPath:[appBundle pathForResource:#"FILE_NAME" ofType:#"mp3"]];
AVAudioFile *asset = [[AVAudioFile alloc] initForReading:url error:&error];
[_audioPlayer scheduleFile:asset atTime:nil completionHandler:nil];
[_audioPlayer play];
Here is the code i've tried to use for AVAudioPlayer, but does not work:
NSError *audioError;
AVAudioPlayer* player = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:#"FILE_NAME" ofType:#"mp3"]] error:&audioError];
player.numberOfLoops = MAXFLOAT;
player.delegate = self;
[player play];
I am using WatchKit 5.0(+).

Answer 1

You can loop your AVAudioFile by recursively scheduling it:
__block __weak void (^weakSheduleFile)(void);
void (^scheduleFile)(void);
weakSheduleFile = scheduleFile = ^{ [self->_audioPlayer scheduleFile:asset atTime:nil completionHandler:weakSheduleFile]; };
scheduleFile();
I'm not sure if this will be a seamless loop. If it's not, you can try always having two files scheduled:
scheduleFile();
scheduleFile();

Answer 2

If your audio file fits into memory, you could schedule playback as an AVAudioBuffer with the AVAudioPlayerNodeBufferLoops option (N.B. only tested on simulator!):
AVAudioFormat *outputFormat = [_audioPlayer outputFormatForBus:0];
__block AVAudioPCMBuffer *srcBuffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:asset.processingFormat frameCapacity:(AVAudioFrameCount)asset.length];
if (![asset readIntoBuffer:srcBuffer error:&error]) {
NSLog(#"Read error: %#", error);
abort();
}
AVAudioPCMBuffer *dstBuffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:outputFormat frameCapacity:(AVAudioFrameCount)asset.length];
AVAudioConverter *converter = [[AVAudioConverter alloc] initFromFormat:srcBuffer.format toFormat:dstBuffer.format];
AVAudioConverterOutputStatus status = [converter convertToBuffer:dstBuffer error:&error withInputFromBlock:^AVAudioBuffer * _Nullable(AVAudioPacketCount inNumberOfPackets, AVAudioConverterInputStatus * _Nonnull outStatus) {
if (srcBuffer) {
AVAudioBuffer *result = srcBuffer;
srcBuffer = NULL;
*outStatus = AVAudioConverterInputStatus_HaveData;
return result;
} else {
*outStatus = AVAudioConverterInputStatus_EndOfStream;
return NULL;
}
}];
assert(status != AVAudioConverterOutputStatus_Error);
[_audioPlayer scheduleBuffer:dstBuffer atTime:nil options:AVAudioPlayerNodeBufferLoops completionHandler:nil];
[_audioPlayer play];