ShazamKit catalog generation for an audio file

ShazamKitCatalogGeneration.swift

import AVFoundation
import ShazamKit

func generateSignatureAndCatalogFromAudioFile() {

    // this function takes an audio file and creates a ShazamKit signature for it,
    // creates a media item to associate with the signature,
    // creates a custom catalog with one entry (the audio signature + media item),
    // and writes it out to disk as a .shazamcatalog file
  
    // this example is full of force-unwrapped optionals... please use proper do/try/catch blocks in real code!


    // assuming you have a sound file in your bundle called soundtrack.m4a
    let url = Bundle.main.url(forResource: "soundtrack", withExtension: "m4a")!

    let audioFile = try? AVAudioFile(forReading: url)

    // audio format ShazamKit will understand
    let newFormat = AVAudioFormat(standardFormatWithSampleRate: 48000, channels: 1)

    // to convert from audiofile buffer to ShazamKit buffer
    let converter = AVAudioConverter(from: audioFile!.processingFormat, to: newFormat!)

    // buffer for audio file to read into
    let soundtrackPCMBuffer = AVAudioPCMBuffer(pcmFormat: audioFile!.processingFormat, frameCapacity: AVAudioFrameCount(audioFile!.length))

    // buffer to convert into and then use for creating ShazamKit signature
    let convertedPCMBuffer = AVAudioPCMBuffer(pcmFormat: newFormat!, frameCapacity: AVAudioFrameCount(audioFile!.length))


    do {
        // read the audio file into the buffer
        try audioFile?.read(into: soundtrackPCMBuffer!)

        // convert the audio file buffer
        try converter!.convert(to: convertedPCMBuffer!, from: soundtrackPCMBuffer!)

    } catch {
        print("read/convert into error!! \(error)")
    }

    let signatureGenerator = SHSignatureGenerator()
    do {
        // generate signature from the converted buffer
        try signatureGenerator.append(convertedPCMBuffer!, at: nil)
    } catch {
        print("signature generation error!! \(error)")
    }

    let signature = signatureGenerator.signature()

    // see if we got a signature and if it has a duration
    print("signature: \(String(describing: signature))")
    print("signature duration: \(signature.duration)")


    // create a custom catalog
    let catalog = SHCustomCatalog()

    // create a media item to associate with the signature
    let item = SHMediaItem(properties: [
        .artist: "Artist",
        .subtitle: "Subtitle",
        .shazamID: "123",
        // ...
    ])

    // add the item referencing the signature
    try? catalog.addReferenceSignature(signature, representing: [item])


    // write out the catalog to a file
    let tempURL = URL(fileURLWithPath: NSTemporaryDirectory())
        .appendingPathComponent(UUID().uuidString)
        .appendingPathExtension("shazamcatalog")

    do {
        // do the thing
        try catalog.write(to: tempURL)

        // print the file URL of the .shazamcatalog file
        print("\(tempURL)")
    } catch {
        print("Export error: \(error)")
    }
}