AudioKit AKNodeRecorder create empty audio file

Question

I am developing an application for iOS, and I need some audio processing methods so I employed AudioKit which is awesome. However I failed using AKNodeRecorder when trying recording the effects into audio file.

I have tried using the AudioKitPlayground(4.5.3) to test AKNodeRecorder, but got an empty audio file after recording the sound generated by the 'keyboard'.

So I create a project for iOS by Xcode(10.1), and add some Objective-C code like this:

........

NSError *error = nil;
AudioFormatID formatId = kAudioFormatLinearPCM;
NSDictionary *dict = @{
                       @"AVFormatIDKey" : @(formatId),
                       @"AVSampleRateKey" : @(44100),
                       @"AVNumberOfChannelsKey" : @(2),
                       };
AKAudioFile *audioFile = [[AKAudioFile alloc] initForWriting:soundFileURL settings:dict error:&error];
if (error) {
    NSLog(@"AKAudioFile init error: %@", error);
}
AKNodeRecorder *akNodeRecorder = [[AKNodeRecorder alloc] initWithNode:self.akMixer file:audioFile error:&error];
if (error) {
    NSLog(@"AKNodeRecorder init error: %@", error);
}
[akNodeRecorder recordAndReturnError:&error];
if (error) {
    NSLog(@"recording error: %@", error);
}
[self.akAudioPlayer playFrom:0.0];
if (self.isChooseBackgroundMusic) {               
    [self.musicPlayer playFrom:0.0];
}
[akNodeRecorder stop];

........

And the self.akMixer here is like this:

self.akMixer = [[AKMixer alloc] init:@[self.akAudioPlayer, self.musicPlayer]];

But, I got am empty file too.

Is there something wrong in my code or I have misunderstood AKNodeRecorder? Any help? Many thanks!

I am facing a same problem in swift. Did you figure out yet? — Muhammad Haroon Iqbal, Jan 11 '21 at 07:59

score 0 · Answer 1 · answered Jan 12 '21 at 07:24

I had a same problem in swift, I am able to resolve this issue by declaring all variables related Audio (like mixers and players) as global. You can see in code below. Hope this thing will work in Objective C too.

class SongRecordingVC: UIViewController {

    var micMixer : AKMixer!
    var micBooster: AKBooster!
    var karaokePlayer : AKPlayer!
    var karaokeMixer: AKMixer!
    var recordingMixer: AKMixer!
    var recordingDummyMixer: AKMixer!
    var outputMixer: AKMixer!
    
    var songPlayer: AVAudioPlayer?

AudioKit AKNodeRecorder create empty audio file

1 Answers1