LinearPCMRecording class in AudioUtil

AudioUtil.swift

    /**
     Leaner PCM recording setting model
     This class represents Linear PCM recording related settings
     */
    public class LinearPCMRecording {
        
        //
        // these constants are only to avoid magic numbers
        //
        private static let SAMPLE_RATE_16_KHZ = 16_000
        private static let BIT_DEPTH_16 = 16
        private static let CHANNEL_MONO = 1
        
        //
        // bit rate will be automatically calculated from sampleRate, bitDepth and channelCount
        //
        public private(set) var bitRate = SAMPLE_RATE_16_KHZ * BIT_DEPTH_16 * CHANNEL_MONO
        private func updateBitRate(){
            Logger.logIt(#function)
            bitRate = sampleRate * bitDepth * channelCount
        }
        
        //
        // Linear PCM sample rate for AVAudioRecorder
        //
        public var sampleRate:Int = SAMPLE_RATE_16_KHZ {
            willSet {
                updateBitRate()
                updateLinearPCMRecordingSettings()
            }
        }
        
        //
        // Linear PCM channel count for AVAudioRecorder
        //
        public var channelCount:Int = CHANNEL_MONO {
            willSet {
                updateBitRate()
                updateLinearPCMRecordingSettings()
            }
        }
        
        //
        // Linear PCM bit depth for AVAudioRecorder
        //
        public var bitDepth:Int = BIT_DEPTH_16 {
            willSet {
                updateBitRate()
                updateLinearPCMRecordingSettings()
            }
        }
        
        //
        // Linear PCM format settings for AVAudioRecorder
        //
        public var isFormatFloat = false {
            didSet {
                updateLinearPCMRecordingSettings()
            }
        }
        public var isFormatBigEndian = false {
            didSet {
                updateLinearPCMRecordingSettings()
            }
        }
        
        //
        // Designed initilizer
        //
        public init(sampleRate: Int, channelCount: Int, bitDepth: Int){
            self.sampleRate = sampleRate
            self.channelCount = channelCount
            self.bitDepth = bitDepth
            updateBitRate()
        }
        
        //
        // Convinience initilizer
        //
        public convenience init(sampleRate: Int, channelCount: Int, bitDepth: Int, isFormatFloat: Bool, isFormatBigEndian: Bool){
            
            self.init(sampleRate: sampleRate, channelCount: channelCount, bitDepth: bitDepth)
            
            self.isFormatFloat = isFormatFloat
            self.isFormatBigEndian = isFormatBigEndian
            
            updateLinearPCMRecordingSettings()
        }
        
        //
        // Recorder setting for Linear PCM
        //
        public static let LINEAR_PCM_RECODING_SETTINGS_DEFAULT = [
            AVFormatIDKey: kAudioFormatLinearPCM,
            AVSampleRateKey: SAMPLE_RATE_16_KHZ,
            AVNumberOfChannelsKey: CHANNEL_MONO,
            AVLinearPCMBitDepthKey: BIT_DEPTH_16,
            AVLinearPCMIsFloatKey: false
            ] as [String : Any]
        
        public var recordingSettings = LINEAR_PCM_RECODING_SETTINGS_DEFAULT
        
        private func updateLinearPCMRecordingSettings(){
            
            Logger.logIt(#function)
            
            recordingSettings = [
                AVFormatIDKey: kAudioFormatLinearPCM,
                AVSampleRateKey: sampleRate,
                AVNumberOfChannelsKey: channelCount,
                AVLinearPCMBitDepthKey: bitDepth,
                AVLinearPCMIsFloatKey: isFormatFloat,
                AVLinearPCMIsBigEndianKey: isFormatBigEndian
                ] as [String : Any]
        }
        
        //
        // Default Linear PCM recording settings
        //
        public static let `default` = LinearPCMRecording(sampleRate: SAMPLE_RATE_16_KHZ, channelCount: CHANNEL_MONO, bitDepth: BIT_DEPTH_16)
    }

// rest is here: https://stackoverflow.com/questions/59622288/how-to-encode-self-delimited-opus-in-ios