在我的 iOS 应用程序中,使用 swift
我正在从数字健康设备 (BLE) 获取音频。以音频数据的形式,听到心跳声。
我们对接收到的数据应用 ADPCM 解码器。播放时有背景噪音和心跳声。
我们应用过滤器来消除背景噪音。使用苹果的DSP代码,应用低通滤波器和高通滤波器。
音频文件在苹果的DSP滤波器代码中播放良好。 在Apple的DSP应用中,他们使用的是AVAudioEngine。
在我的演示代码中,我需要音频心跳进行过滤,使用了音频单元和 TPCircularBuffer。并使用Apple的DSP高通和低通滤波器。
在演示项目中代码是这样的
let musicProvider = FilterableMusicProvider()
var page = [Float]()
// Code in viewDidLoad
让样本= musicProvider.loadAudioSamples(样本:audioData.map { 浮点数($0) })
musicProvider.selectedSectionIndex = 0
musicProvider.parameters.first?.filterType = .lowpass
musicProvider.parameters.first?.frequency = 187.5
musicProvider.parameters.first?.Q = 0.707
musicProvider.parameters.first?.dbGain = 0.0
musicProvider.setSelectedSectionCoefficients()
musicProvider.selectedSectionIndex = 1
musicProvider.parameters[1].filterType = .highpass
musicProvider.parameters[1].frequency = 44.5
musicProvider.parameters[1].Q = 0.272
musicProvider.parameters[1].dbGain = 0.0
musicProvider.setSelectedSectionCoefficients()
var signal = getSignalElement()
while (signal != 0) {
signal = getSignalElement()
}
//Method for playing byte array
func getSignalElement() -> Float {
var lastData = Data()
for signal in page {
let uInt8 =
iirFilterNew.convertDoubleToUInt8(Double(signal))
lastData.append(uInt8)
}
let i16array = lastData.withUnsafeBytes { bufferPointer in
TPCircularBufferProduceBytes(iosAudio.addressOfTPBuffer(), bufferPointer.baseAddress,
UInt32(bufferPointer.count));
}
return page.isEmpty ? 0 : page.removeFirst()
}
//Code for conversion of Float to Double
func convertDoubleToUInt8(value: Double) -> UInt8 {
var val = value
val.round()
if val > 127.0 {
val = 127.0
}
if val < -128.0 {
val = -128.0
}
var signedInt: Int8 = 0
if val.isNaN {
signedInt = 0
} else {
signedInt = Int8(val)
}
return UInt8.init(bitPattern: Int8(signedInt))
}
上面的代码,当我玩的时候,我听不到清晰的心跳声
func applyFilterToData(decoded: Data, filterEnabled: Bool = true) -> Data {
var lastData = Data()
for decodedData in decoded {
let unsignedData = UInt8(decodedData)
let scaledInput = Double(unsignedData) / 128.0 - 1.0 // Assuming 0-255 range
var filteredOutput: Double
if filterEnabled {
filteredOutput = iirFilterNew.filter(scaledInput)
} else {
filteredOutput = scaledInput
}
// Scaling output (adjust if needed)
let scaledOutput = filteredOutput * 128.0 + 128.0
let outputUInt8 = UInt8(clamping: Int(round(scaledOutput)))
lastData.append(outputUInt8)
}
return lastData
}
// Improved conversion with clamping
func convertDoubleToUInt8(value: Double) -> UInt8 {
return UInt8(clamping: Int(round(value)))
}