我正在从AKLazyTap捕获音频，并在应用程序的音频运行时在后台将累积的copy(from:readOffset:frames)渲染为音频文件。这很好用，但是我想添加淡入/淡出效果。我看到了为单个AVAudioPCMBuffer添加淡入的便捷扩展，但是我不确定如何在数组上进行淡入淡出。我曾想连接缓冲区，但似乎对此没有支持。有人知道当前是否可行？基本上，它需要与func renderBufferedAudioToFile(_ audioBuffers: [AVAudioPCMBuffer], withStartOffset startOffset: Int, endOffset: Int, fadeIn: Float64, fadeOut: Float64, atURL url: URL) {
// strip off the file name
let name = String(url.lastPathComponent.split(separator: ".")[0])
var url = self.module.stateManager.audioCacheDirectory
// UNCOMPRESSED
url = url.appendingPathComponent("\(name).caf")
let format = Conductor.sharedInstance.sourceMixer.avAudioNode.outputFormat(forBus: 0)
var settings = format.settings
settings["AVLinearPCMIsNonInterleaved"] = false
// temp buffer for fades
let totalFrameCapacity = audioBuffers.reduce(0) { $0 + $1.frameLength }
guard let tempAudioBufferForFades = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: totalFrameCapacity) else {
print("Failed to create fade buffer!")
return
}
// write ring buffer to file.
let file = try! AVAudioFile(forWriting: url, settings: settings)
var writeOffset: AVAudioFrameCount = 0
for i in 0 ..< audioBuffers.count {
var buffer = audioBuffers[i]
let channelCount = Int(buffer.format.channelCount)
if i == 0 && startOffset != 0 {
// copy a subset of samples in the buffer
if let subset = buffer.copyFrom(startSample: AVAudioFrameCount(startOffset)) {
buffer = subset
}
} else if i == audioBuffers.count - 1 && endOffset != 0 {
if let subset = buffer.copyTo(count: AVAudioFrameCount(endOffset)) {
buffer = subset
}
}
// write samples into single, long buffer
for i in 0 ..< buffer.frameLength {
for n in 0 ..< channelCount {
tempAudioBufferForFades.floatChannelData?[n][Int(i + writeOffset)] = (buffer.floatChannelData?[n][Int(i)])!
}
}
print("buffer \(i), writeOffset = \(writeOffset)")
writeOffset = writeOffset + buffer.frameLength
}
// update!
tempAudioBufferForFades.frameLength = totalFrameCapacity
if let bufferWithFades = tempAudioBufferForFades.fade(inTime: fadeIn, outTime: fadeOut) {
try! file.write(from: bufferWithFades)
}
}
类似的东西，但也需要具有写偏移量...
或者也许有一种更简单的方法？
好的，在研究了一些相关的AK代码之后，我尝试将缓冲区数据直接复制到单个长缓冲区中，然后应用渐变便利功能。但是，这给了我一个空文件（4k）。在这里我没有看到一些明显的错误吗？
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