Tap installed on audio engine only producing short files - ios

Question

I am working on an app that allows the user to record audio, play it back while changing the pitch then record what they have done as a separate file.
The code seems to be working but the new file has a duration of only 0.37 seconds (original 5 seconds).
I am guessing when I write from the buffer it keeps saving over itself, thus leaving me with just the last segment. If this is my issue, how do I append the file instead of writing over it?
let recordSettings:[String : AnyObject] = [
AVFormatIDKey: NSNumber(unsignedInt:kAudioFormatAppleLossless),
AVEncoderAudioQualityKey : AVAudioQuality.Max.rawValue,
AVEncoderBitRateKey : 320000,
AVNumberOfChannelsKey: 2,
AVSampleRateKey : 44100.0
]
var outputFile = AVAudioFile()
let format = NSDateFormatter()
format.dateFormat="dd-HH-mm-ss"
let currentFileName = "recording-\(format.stringFromDate(NSDate())).m4a"
print(currentFileName)
let documentsDirectory = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
self.url2 = documentsDirectory.URLByAppendingPathComponent(currentFileName)
let inputNode = engine.inputNode
let bus = 0
engine.mainMixerNode.installTapOnBus(bus, bufferSize: 2048, format: self.engine.mainMixerNode.inputFormatForBus(0)) {
(buffer: AVAudioPCMBuffer!, time: AVAudioTime!) -> Void in
do {
let outputFile = try AVAudioFile(forWriting: self.url2, settings: recordSettings, commonFormat: AVAudioCommonFormat.PCMFormatFloat32, interleaved: false)
try outputFile.writeFromBuffer(buffer)
outputFile.framePosition = outputFile.length
} catch let error as NSError {
NSLog("Error writing %#", error.localizedDescription)
}
}
Updated code creating a file with a duration of 0.0:
func play() {
let duration = CMTimeGetSeconds(AVAsset(URL: url).duration)
print("Duration")
print(duration)
let file = try! AVAudioFile(forReading: url)
let buffer = AVAudioPCMBuffer(PCMFormat: file.processingFormat, frameCapacity: AVAudioFrameCount(file.length))
do {
try file.readIntoBuffer(buffer)
} catch _ {
}
engine = AVAudioEngine()
player = AVAudioPlayerNode()
pitch.pitch = 500
engine.attachNode(player)
engine.attachNode(pitch)
engine.connect(player, to: pitch, format: buffer.format)
engine.connect(pitch, to: engine.mainMixerNode, format: nil)
let format = NSDateFormatter()
format.dateFormat="dd-HH-mm-ss"
let currentFileName = "recording-\(format.stringFromDate(NSDate())).m4a"
print(currentFileName)
let documentsDirectory = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
self.url2 = documentsDirectory.URLByAppendingPathComponent(currentFileName)
let outputFile = try! AVAudioFile(forWriting: url2, settings: [
AVFormatIDKey: NSNumber(unsignedInt:kAudioFormatAppleLossless),
AVEncoderAudioQualityKey : AVAudioQuality.Max.rawValue,
AVEncoderBitRateKey : 320000,
AVNumberOfChannelsKey: 2,
AVSampleRateKey : 44100.0
])
done = false
distortion.installTapOnBus(0, bufferSize: 2048, format: outputFile.processingFormat) {
(buffer: AVAudioPCMBuffer!, time: AVAudioTime!) in
let dataptrptr = buffer.floatChannelData
let dataptr = dataptrptr.memory
let datum = dataptr[Int(buffer.frameLength) - 1]
if self.done && fabs(datum) < 0.000001 {
print("stopping")
self.engine.stop()
return
}
do {
try outputFile.writeFromBuffer(buffer)
} catch let error as NSError {
NSLog("Error writing %#", error.localizedDescription)
}
}
player.scheduleBuffer(buffer, atTime: nil, options: AVAudioPlayerNodeBufferOptions.Loops, completionHandler: {
dispatch_async(dispatch_get_main_queue(),{
self.done = true
self.player.stop()
self.engine.stop()
print("complete")
})
})
engine.prepare()
do {
try engine.start()
player.play()
} catch _ {
print("Play session Error")
}
}

Answer 1

Keep in mind that the installTapOnBus handler will be called many times: every time the buffer fills up. Think of it as a loop. Thus it makes no sense to create the output file each time through that loop! You want to create the output file once and then write to it repeatedly. Thus, your overall structure needs to look like this:
let outfile = try! AVAudioFile(forWriting: outurl, settings: // ...
node.installTapOnBus(bus, bufferSize: size, format: outfile.processingFormat) {
(buffer : AVAudioPCMBuffer!, time : AVAudioTime!) in
do {
try outfile.writeFromBuffer(buffer)
} catch {
print(error)
}
}
The other thing to remember is that your buffer will fill-and-write exactly so long as the engine keeps running, so don't stop the engine prematurely (I don't know whether you're doing that, but it's important to keep in mind).