DSWaveformImage - Realtime audio waveform rendering

DSWaveformImage offers a few interfaces for the purpose of drawing the envelope waveform of audio data in iOS, iPadOS and Mac Catalyst. To do so, you can use

• WaveformImageDrawer to generate a waveform UIImage from an audio file
• WaveformImageView to render a static waveform from an audio file or
• WaveformLiveView to realtime render a waveform of live audio data (e.g. from AVAudioRecorder)

Additionally, you can get a waveform's (normalized) [Float] samples directly as well by creating an instance of WaveformAnalyzer.

More related iOS Controls

You may also find the following iOS controls written in Swift interesting:

• SwiftColorWheel - a delightful color picker
• QRCode - a customizable QR code generator

If you really like this library (aka Sponsoring)

I'm doing all this for fun and joy and because I strongly believe in the power of open source. On the off-chance though, that using my library has brought joy to you and you just feel like saying "thank you", I would smile like a 4-year old getting a huge ice cream cone, if you'd support my via one of the sponsoring buttons ☺️💕

If you're feeling in the mood of sending someone else a lovely gesture of appreciation, maybe check out my iOS app 💌 SoundCard to send them a real postcard with a personal audio message.

Installation

• use SPM: add https://github.com/dmrschmidt/DSWaveformImage and set "Up to Next Major" with "10.0.0"

Deprecated or discouraged but still possible alternative ways for older apps:

• since it has no other dependencies you may simply copy the DSWaveformImage folder directly into your project
• use carthage: github "dmrschmidt/DSWaveformImage" ~> 7.0
• or, sunset since 6.1.1: use cocoapods: pod 'DSWaveformImage', '~> 6.1'

Usage

async / await Support

The public API has been updated in 9.1 to support async / await. See the example app for an illustration.

public class WaveformAnalyzer {
    func samples(count: Int, qos: DispatchQoS.QoSClass = .userInitiated) async throws -> [Float]
}

public class WaveformImageDrawer {
    public func waveformImage(
        fromAudioAt audioAssetURL: URL,
        with configuration: Waveform.Configuration,
        qos: DispatchQoS.QoSClass = .userInitiated
    ) async throws -> UIImage
}

SwiftUI Support

All DSWaveformImage views, while native UIKit, can be used from within SwiftUI easily by wrapping them as UIViewRepresentable.

Check out WaveformImageViewUI in the example app for a copy & paste ready starting point.

A more full-featured out of the box SwiftUI support will be coming eventually. Until then it should be straightforward to use via UIViewRepresentable.

Configuration

Note: Calculations are always performed and returned on a background thread, so make sure to return to the main thread before doing any UI work.

Check Waveform.Configuration in WaveformImageTypes for various configuration options.

WaveformImageDrawer - creates a UIImage waveform from an audio file:

let waveformImageDrawer = WaveformImageDrawer()
let audioURL = Bundle.main.url(forResource: "example_sound", withExtension: "m4a")!
waveformImageDrawer.waveformImage(fromAudioAt: audioURL, with: .init(
                                  size: topWaveformView.bounds.size,
                                  style: .filled(UIColor.black),
                                  position: .top) { image in
    // need to jump back to main queue
    DispatchQueue.main.async {
        self.topWaveformView.image = image
    }
}

WaveformImageView - renders a one-off waveform from an audio file:

let audioURL = Bundle.main.url(forResource: "example_sound", withExtension: "m4a")!
waveformImageView = WaveformImageView(frame: CGRect(x: 0, y: 0, width: 500, height: 300)
waveformImageView.waveformAudioURL = audioURL

WaveformLiveView - renders a live waveform from (0...1) normalized samples:

Find a full example in the sample project's RecordingViewController.

let waveformView = WaveformLiveView()

// configure and start AVAudioRecorder
let recorder = AVAudioRecorder()
recorder.isMeteringEnabled = true // required to get current power levels

// after all the other recording (omitted for focus) setup, periodically (every 20ms or so):
recorder.updateMeters() // gets the current value
let currentAmplitude = 1 - pow(10, recorder.averagePower(forChannel: 0) / 20)
waveformView.add(sample: currentAmplitude)

WaveformAnalyzer - calculates an audio file's waveform sample:

let audioURL = Bundle.main.url(forResource: "example_sound", withExtension: "m4a")!
waveformAnalyzer = WaveformAnalyzer(audioAssetURL: audioURL)
waveformAnalyzer.samples(count: 200) { samples in
    print("so many samples: \(samples)")
}

Playback Indication

If you're playing back audio files and would like to indicate the playback progress to your users, you can find inspiration in this ticket. There's various other ways of course, depending on your use case and design. Using WaveformLiveView may be another one in conjunction with AVAudioPlayer (note that AVPlayer does not offer the same simple access to its audio metering data, so is not as suitable out of the box).

Loading remote audio files from URL

For one example way to display waveforms for audio files on remote URLs see https://github.com/dmrschmidt/DSWaveformImage/issues/22.

What it looks like

Waveforms can be rendered in 3 different styles: .filled, .gradient and .striped.

Similarly, there are 3 positions relative to the canvas, .top, .middle and .bottom.

The effect of each of those can be seen here:

Live waveform rendering

https://user-images.githubusercontent.com/69365/127739821-061a4345-0adc-4cc1-bfd6-f7cfbe1268c9.mov

Migration

In 9.0.0 a few public API's have been slightly changed to be more concise. All types have also been grouped under the Waveform enum-namespace. Meaning WaveformConfiguration for instance has become Waveform.Configuration and so on.

In 7.0.0 colors have moved into associated values on the respective style enum.

Waveform and the UIImage category have been removed in 6.0.0 to simplify the API. See Usage for current usage.

See it live in action

SoundCard - postcards with sound lets you send real, physical postcards with audio messages. Right from your iOS device.

DSWaveformImage is used to draw the waveforms of the audio messages that get printed on the postcards sent by SoundCard - postcards with audio.

Download SoundCard on the App Store.