| @preconcurrency import AVFoundation |
| import Foundation |
|
|
| final class BufferConverter { |
| private final class Box<T>: @unchecked Sendable { var value: T; init(_ value: T) { self.value = value } } |
| enum ConverterError: Swift.Error { |
| case failedToCreateConverter |
| case failedToCreateConversionBuffer |
| case conversionFailed(NSError?) |
| } |
|
|
| private var converter: AVAudioConverter? |
|
|
| func convert(_ buffer: AVAudioPCMBuffer, to format: AVAudioFormat) throws -> AVAudioPCMBuffer { |
| let inputFormat = buffer.format |
| if inputFormat == format { |
| return buffer |
| } |
| if converter == nil || converter?.outputFormat != format { |
| converter = AVAudioConverter(from: inputFormat, to: format) |
| converter?.primeMethod = .none |
| } |
| guard let converter else { throw ConverterError.failedToCreateConverter } |
|
|
| let sampleRateRatio = converter.outputFormat.sampleRate / converter.inputFormat.sampleRate |
| let scaledInputFrameLength = Double(buffer.frameLength) * sampleRateRatio |
| let frameCapacity = AVAudioFrameCount(scaledInputFrameLength.rounded(.up)) |
| guard let conversionBuffer = AVAudioPCMBuffer(pcmFormat: converter.outputFormat, frameCapacity: frameCapacity) |
| else { |
| throw ConverterError.failedToCreateConversionBuffer |
| } |
|
|
| var nsError: NSError? |
| let consumed = Box(false) |
| let inputBuffer = buffer |
| let status = converter.convert(to: conversionBuffer, error: &nsError) { _, statusPtr in |
| if consumed.value { |
| statusPtr.pointee = .noDataNow |
| return nil |
| } |
| consumed.value = true |
| statusPtr.pointee = .haveData |
| return inputBuffer |
| } |
| if status == .error { |
| throw ConverterError.conversionFailed(nsError) |
| } |
| return conversionBuffer |
| } |
| } |
|
|
