How to generate audio wave form programmatically while recording Voice in iOS?

Question

How to generate audio wave form programmatically while recording Voice in iOS?

Answer 1

I was searching the same thing. (Making wave from the data of the audio recorder). I found some library that might be helpful and worth to check the code to understand the logic behind this.

The calculation is all based with sin and mathematic formula. This is much simple if you take a look to the code!

https://github.com/stefanceriu/SCSiriWaveformView

or

https://github.com/raffael/SISinusWaveView

This is only few examples that you can find on the web.

Answer 2

You should check out EZAudio (https://github.com/syedhali/EZAudio), specifically the EZRecorder and the EZAudioPlot (or GPU-accelerated EZAudioPlotGL).

There is also an example project that does exactly what you want, https://github.com/syedhali/EZAudio/tree/master/EZAudioExamples/iOS/EZAudioRecordExample

EDIT: Here's the code inline

/// In your interface

/**
 Use a OpenGL based plot to visualize the data coming in
 */
@property (nonatomic,weak) IBOutlet EZAudioPlotGL *audioPlot;
/**
 The microphone component
 */
@property (nonatomic,strong) EZMicrophone *microphone;
/**
 The recorder component
 */
@property (nonatomic,strong) EZRecorder *recorder;

...

/// In your implementation

// Create an instance of the microphone and tell it to use this view controller instance as the delegate
-(void)viewDidLoad {
    self.microphone = [EZMicrophone microphoneWithDelegate:self startsImmediately:YES];
}

// EZMicrophoneDelegate will provide these callbacks
-(void)microphone:(EZMicrophone *)microphone
 hasAudioReceived:(float **)buffer
   withBufferSize:(UInt32)bufferSize
withNumberOfChannels:(UInt32)numberOfChannels {
  dispatch_async(dispatch_get_main_queue(),^{
    // Updates the audio plot with the waveform data
    [self.audioPlot updateBuffer:buffer[0] withBufferSize:bufferSize];
  });
}

-(void)microphone:(EZMicrophone *)microphone hasAudioStreamBasicDescription:(AudioStreamBasicDescription)audioStreamBasicDescription {
  // The AudioStreamBasicDescription of the microphone stream. This is useful when configuring the EZRecorder or telling another component what audio format type to expect.

  // We can initialize the recorder with this ASBD
  self.recorder = [EZRecorder recorderWithDestinationURL:[self testFilePathURL]
                                         andSourceFormat:audioStreamBasicDescription];

}

-(void)microphone:(EZMicrophone *)microphone
    hasBufferList:(AudioBufferList *)bufferList
   withBufferSize:(UInt32)bufferSize
withNumberOfChannels:(UInt32)numberOfChannels {

  // Getting audio data as a buffer list that can be directly fed into the EZRecorder. This is happening on the audio thread - any UI updating needs a GCD main queue block. This will keep appending data to the tail of the audio file.
  if( self.isRecording ){
    [self.recorder appendDataFromBufferList:bufferList
                             withBufferSize:bufferSize];
  }

}

Answer 3

If you want real-time graphics derived from mic input, then use the RemoteIO Audio Unit, which is what most native iOS app developers use for low latency audio, and Metal or Open GL for drawing waveforms, which will give you the highest frame rates. You will need completely different code from that provided in your question to do so, as AVAssetRecording, Core Graphic line drawing and png rendering are far far too slow to use.

Update: with iOS 8 and newer, the Metal API may be able to render graphic visualizations with even greater performance than OpenGL.

Uodate 2: Here are some code snippets for recording live audio using Audio Units and drawing bit maps using Metal in Swift 3: https://gist.github.com/hotpaw2/f108a3c785c7287293d7e1e81390c20b