我有一个扩展名为 .m4a 的音频文件，我希望将其转换为 .caf 文件。我有一个功能准备就绪并且可以工作。它工作正常但是当通过代码编辑音频时（改变速度、音高、回声和混响）它返回一个错误说明：
"failed Optional(Error Domain=AVFoundationErrorDomain Code=-11800 "操作无法完成" UserInfo={NSLocalizedFailureReason=发生未知错误（-12780），NSLocalizedDescription=操作无法完成，NSUnderlyingError=0x600001878a80 {Error Domain =NSOSStatusErrorDomain Code=-12780 "(null)"}})"
转换使用的函数是：
func convertAudioFileToCaf(inputURL: URL, outputURL: URL, completion: @escaping (Bool) -> Void) {
let asset = AVURLAsset(url: inputURL, options: nil)
let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetPassthrough)
exportSession?.outputURL = outputURL
exportSession?.outputFileType = AVFileType.caf
exportSession?.exportAsynchronously(completionHandler: {
switch exportSession!.status {
case .completed:
completion(true)
case .failed:
print("failed \(String(describing: exportSession?.error))")
completion(false)
case .cancelled:
print("cancelled \(String(describing: exportSession?.error))")
completion(false)
default:
break
}
})
}
文件正在播放，但编辑时出现错误。 添加效果的函数：
func play(){
do {
guard let url = urlSong else{return}
let sourceFileURL = url // it is .caf file url of the function convertAudioFileToCaf.
sourceFile = try AVAudioFile(forReading: sourceFileURL)
format = sourceFile.processingFormat
} catch {
print("Unable to load the source audio file: \(error.localizedDescription).")
}
engine.attach(player)
engine.attach(reverb)
engine.attach(playbackRateEffect)
engine.attach(pitchEffect)
// Set the desired reverb parameters.
reverb.loadFactoryPreset(.cathedral)
reverb.wetDryMix = 50
playbackRateEffect.rate = 2
engine.attach(playbackRateEffect)
//Pitch
pitchEffect.rate = 1
pitchEffect.pitch = -1500
engine.attach(pitchEffect)
//Echo
// echoEffect.delayTime = TimeInterval(60)
// engine.attach(echoEffect)
// Connect the nodes.
engine.connect(player, to: playbackRateEffect, format: sourceFile.processingFormat)
engine.connect(playbackRateEffect, to: pitchEffect, format: sourceFile.processingFormat)
// engine.connect(pitchEffect, to: echoEffect, format: sourceFile.processingFormat)
engine.connect(pitchEffect, to: reverb, format: sourceFile.processingFormat)
engine.connect(reverb, to: engine.mainMixerNode, format: sourceFile.processingFormat)
player.scheduleFile(sourceFile, at: nil)
do {
let maxFrames: AVAudioFrameCount = 4096
try engine.enableManualRenderingMode(.offline, format: format,
maximumFrameCount: maxFrames)
} catch {
print("Enabling manual rendering mode failed.")
}
do {
try engine.start()
player.play()
} catch {
fatalError("Unable to start audio engine: \(error).")
}
let buffer = AVAudioPCMBuffer(pcmFormat: engine.manualRenderingFormat,
frameCapacity: engine.manualRenderingMaximumFrameCount)!
do {
let outputURL = documentsURL.appendingPathComponent("effectedSound\(Int(Date().timeIntervalSince1970)).caf")
outputFile = try AVAudioFile(forWriting: outputURL, settings: sourceFile.fileFormat.settings)
newCafUrl = outputURL
print(outputURL)
} catch {
print("Unable to open output audio file")
}
while engine.manualRenderingSampleTime < sourceFile.length {
do {
let frameCount = sourceFile.length - engine.manualRenderingSampleTime
let framesToRender = min(AVAudioFrameCount(frameCount), buffer.frameCapacity)
let status = try engine.renderOffline(framesToRender, to: buffer)
let ct = buffer.frameCapacity
if status == .success{
try outputFile.write(from: buffer)
let dataptrptr = buffer.floatChannelData!
let dataptr = dataptrptr.pointee
let datum = abs(dataptr[Int(buffer.frameLength)-1])
print(datum)
if datum < 0.00001 && true {
break
}
} else{
print("Error while writing file")
}
} catch {
fatalError("The manual rendering failed: \(error).")
}
}
let outM4aURL = documentsURL.appendingPathComponent("equalized\(Int(Date().timeIntervalSince1970)).m4a")
convertAudioFileToM4a(inputURL: newCafUrl!, outputURL: outM4aURL) { success in
print(outM4aURL)
}
// Stop the player node and engine.
player.stop()
engine.stop()
}