wehub-resource-sync
109 lines
3.9 KiB
Swift
109 lines
3.9 KiB
Swift
//
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// BuddyAudioConversionSupport.swift
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// leanring-buddy
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//
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// Shared audio conversion helpers for voice transcription providers.
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//
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import AVFoundation
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import Foundation
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final class BuddyPCM16AudioConverter {
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private let targetAudioFormat: AVAudioFormat
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private var audioConverter: AVAudioConverter?
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private var currentInputFormatDescription: String?
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init(targetSampleRate: Double) {
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self.targetAudioFormat = AVAudioFormat(
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commonFormat: .pcmFormatInt16,
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sampleRate: targetSampleRate,
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channels: 1,
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interleaved: true
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)!
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}
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func convertToPCM16Data(from audioBuffer: AVAudioPCMBuffer) -> Data? {
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let inputFormatDescription = audioBuffer.format.settings.description
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if currentInputFormatDescription != inputFormatDescription {
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audioConverter = AVAudioConverter(from: audioBuffer.format, to: targetAudioFormat)
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currentInputFormatDescription = inputFormatDescription
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}
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guard let audioConverter else { return nil }
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let sampleRateRatio = targetAudioFormat.sampleRate / audioBuffer.format.sampleRate
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let outputFrameCapacity = AVAudioFrameCount(
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(Double(audioBuffer.frameLength) * sampleRateRatio).rounded(.up) + 32
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)
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guard let outputBuffer = AVAudioPCMBuffer(
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pcmFormat: targetAudioFormat,
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frameCapacity: outputFrameCapacity
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) else {
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return nil
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}
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var hasProvidedSourceBuffer = false
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var conversionError: NSError?
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let conversionStatus = audioConverter.convert(to: outputBuffer, error: &conversionError) { _, outStatus in
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if hasProvidedSourceBuffer {
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outStatus.pointee = .noDataNow
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return nil
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}
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hasProvidedSourceBuffer = true
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outStatus.pointee = .haveData
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return audioBuffer
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}
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guard conversionStatus != .error else { return nil }
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guard let pcmDataPointer = outputBuffer.audioBufferList.pointee.mBuffers.mData else { return nil }
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let bytesPerFrame = Int(targetAudioFormat.streamDescription.pointee.mBytesPerFrame)
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let byteCount = Int(outputBuffer.frameLength) * bytesPerFrame
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guard byteCount > 0 else { return nil }
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return Data(bytes: pcmDataPointer, count: byteCount)
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}
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}
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enum BuddyWAVFileBuilder {
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static func buildWAVData(
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fromPCM16MonoAudio pcm16AudioData: Data,
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sampleRate: Int,
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channelCount: Int = 1,
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bitsPerSample: Int = 16
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) -> Data {
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let byteRate = sampleRate * channelCount * bitsPerSample / 8
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let blockAlign = channelCount * bitsPerSample / 8
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let dataChunkSize = UInt32(pcm16AudioData.count)
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let fileSize = UInt32(36) + dataChunkSize
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var wavData = Data()
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wavData.append("RIFF".data(using: .ascii)!)
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wavData.append(littleEndianData(from: fileSize))
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wavData.append("WAVE".data(using: .ascii)!)
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wavData.append("fmt ".data(using: .ascii)!)
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wavData.append(littleEndianData(from: UInt32(16)))
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wavData.append(littleEndianData(from: UInt16(1)))
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wavData.append(littleEndianData(from: UInt16(channelCount)))
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wavData.append(littleEndianData(from: UInt32(sampleRate)))
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wavData.append(littleEndianData(from: UInt32(byteRate)))
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wavData.append(littleEndianData(from: UInt16(blockAlign)))
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wavData.append(littleEndianData(from: UInt16(bitsPerSample)))
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wavData.append("data".data(using: .ascii)!)
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wavData.append(littleEndianData(from: dataChunkSize))
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wavData.append(pcm16AudioData)
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return wavData
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}
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private static func littleEndianData<T: FixedWidthInteger>(from value: T) -> Data {
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var littleEndianValue = value.littleEndian
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return Data(bytes: &littleEndianValue, count: MemoryLayout<T>.size)
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}
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}
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