how to play sound with AVAudioPCMBuffer

Question

I Cannot play sound with AVAudioPCMBuffer (though I could play with AVAudioFile). I got this error.

ERROR: AVAudioBuffer.mm:169: -[AVAudioPCMBuffer initWithPCMFormat:frameCapacity:]: required condition is false: isCommonFormat

here is my code below, and I'd really appreciate for your help.

import UIKit
import AVFoundation

class ViewController: UIViewController {

let audioEngine: AVAudioEngine = AVAudioEngine()
let audioFilePlayer: AVAudioPlayerNode = AVAudioPlayerNode()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

    audioEngine.attachNode(audioFilePlayer)

    let filePath: String = NSBundle.mainBundle().pathForResource("test", ofType: "mp3")!
    let fileURL: NSURL = NSURL(fileURLWithPath: filePath)!
    let audioFile = AVAudioFile(forReading: fileURL, error: nil)
    let audioFormat = audioFile.fileFormat
    let audioFrameCount = UInt32(audioFile.length)
    let audioFileBuffer = AVAudioPCMBuffer(PCMFormat: audioFormat, frameCapacity: audioFrameCount)

    var mainMixer = audioEngine.mainMixerNode
    audioEngine.connect(audioFilePlayer, to:mainMixer, format: audioFileBuffer.format)

    audioFilePlayer.scheduleBuffer(audioFileBuffer, atTime: nil, options: nil, completionHandler: nil)

    var engineError: NSError?
    audioEngine.startAndReturnError(&engineError)

    audioFilePlayer.play()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

score 8 · Answer 1 · answered Nov 01 '14 at 03:35

just let me share, this worked somehow, though I don't understand fully.

import UIKit
import AVFoundation

class ViewController: UIViewController {

var audioEngine: AVAudioEngine = AVAudioEngine()
var audioFilePlayer: AVAudioPlayerNode = AVAudioPlayerNode()

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.


    let filePath: String = NSBundle.mainBundle().pathForResource("test", ofType: "mp3")!
    println("\(filePath)")
    let fileURL: NSURL = NSURL(fileURLWithPath: filePath)!
    let audioFile = AVAudioFile(forReading: fileURL, error: nil)
    let audioFormat = audioFile.processingFormat
    let audioFrameCount = UInt32(audioFile.length)
    let audioFileBuffer = AVAudioPCMBuffer(PCMFormat: audioFormat, frameCapacity: audioFrameCount)
    audioFile.readIntoBuffer(audioFileBuffer, error: nil)

    var mainMixer = audioEngine.mainMixerNode
    audioEngine.attachNode(audioFilePlayer)
    audioEngine.connect(audioFilePlayer, to:mainMixer, format: audioFileBuffer.format)
    audioEngine.startAndReturnError(nil)

    audioFilePlayer.play()
    audioFilePlayer.scheduleBuffer(audioFileBuffer, atTime: nil, options: nil, completionHandler: nil)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

score 3 · Answer 2 · edited Nov 04 '14 at 01:58

3

The problem is you're setting the format of your PCM buffer to a non-PCM format. Therefore, you need to create your AVAudioPCMBuffer with the AVAudioFile's processingFormat.

edited Nov 04 '14 at 01:58

lennon310

11,840
11
40
55

answered Nov 04 '14 at 01:12

Bob McCune

31
3

score 3 · Answer 3 · edited Aug 11 '19 at 05:52

3

When using an AVAudioPCMBuffer() you'll get strange errors if you try and use a pcmFormat that's not mixer.outputFormat(forBus: 0)

It will not accept mono channel formats, it will complain about mismatches between the mixer's output format and your format even if you've described them exactly the same and it won't produce errors that explain exactly what the problem is.

edited Aug 11 '19 at 05:52

Jodast

1,193
1
15
32

answered Aug 10 '19 at 23:42

Andrew Hodel

77
3

score 0 · Answer 4 · answered Dec 02 '20 at 03:24

update @Bick's code to Swift 5.3

the code logic is easy to get

Firstly, prepare the data

create an empty AVAudioPCMBuffer, then fill audio data in it.

Secondly, connect the nodes, and use the data to play

import UIKit
import AVFoundation

  class ViewControllerX: UIViewController {

    var audioEngine = AVAudioEngine()
    var audioFilePlayer = AVAudioPlayerNode()

    override func viewDidLoad() {
      super.viewDidLoad()

      // prepare the data
      guard let filePath = Bundle.main.path(forResource: "test", ofType: "mp3") else{ return }

      print("\(filePath)")
      let fileURL = URL(fileURLWithPath: filePath)
      do {
          let audioFile = try AVAudioFile(forReading: fileURL)

          let audioFormat = audioFile.processingFormat
          let audioFrameCount = UInt32(audioFile.length)
          guard let audioFileBuffer = AVAudioPCMBuffer(pcmFormat: audioFormat, frameCapacity: audioFrameCount) else{ return }
          try audioFile.read(into: audioFileBuffer)

          // connect the nodes, and use the data to play
          let mainMixer = audioEngine.mainMixerNode
          audioEngine.attach(audioFilePlayer)
          audioEngine.connect(audioFilePlayer, to: mainMixer, format: audioFileBuffer.format)

          try audioEngine.start()

          audioFilePlayer.play()
          audioFilePlayer.scheduleBuffer(audioFileBuffer, completionHandler: nil)

      } catch {
          print(error)
      }

    }
}

score 0 · Answer 5 · answered Jan 27 '21 at 05:18

Instead of calling audioFile.fileFormat, you should use audioFile.processingFormat as the parameter for AVAudioPCMBuffer contructor.

let buffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat,
                                            frameCapacity: bufferCapacity)

how to play sound with AVAudioPCMBuffer

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