iOS Swift - 合并 .wav 文件并将其转换为 .mp3

Swift
func mergeWavFiles(fileURLs: [URL]) -> URL? {
    guard fileURLs.count > 1 else {
        return nil
    }
    
    let composition = AVMutableComposition()
    
    var nextStartTime = CMTime.zero
    
    for fileURL in fileURLs {
        let asset = AVURLAsset(url: fileURL)
        let track = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)
        
        do {
            try track?.insertTimeRange(CMTimeRangeMake(start: CMTime.zero, duration: asset.duration), of: asset.tracks(withMediaType: .audio)[0], at: nextStartTime)
        } catch {
            print("Error merging audio files: \(error.localizedDescription)")
            return nil
        }
        
        nextStartTime = CMTimeAdd(nextStartTime, asset.duration)
    }
    
    let mergedFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("merged.wav")
    
    guard let exporter = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetAppleM4A) else {
        return nil
    }
    
    exporter.outputFileType = .wav
    exporter.outputURL = mergedFileURL
    
    exporter.exportAsynchronously(completionHandler: {
        if exporter.status == .completed {
            print("Merge complete: \(mergedFileURL)")
        } else if exporter.status == .fAIled {
            print("Error merging audio files: \(exporter.error?.localizedDescription ?? "")")
        }
    })
    
    return mergedFileURL
}

Swift
import AVFoundation
import lame
func convertWavToMp3(wavFileURL: URL, mp3FileURL: URL) {
    let pcmFilePath = wavFileURL.path
    let mp3FilePath = mp3FileURL.path
    
    let read = AVAudioFile(forReading: wavFileURL)
    
    guard let pcmBuffer = AVAudioPCMBuffer(pcmFormat: read.processingFormat, frameCapacity: AVAudioFrameCount(read.length)) else {
        return
    }
    
    do {
        try read.read(into: pcmBuffer)
    } catch {
        print("Error converting audio file: \(error.localizedDescription)")
        return
    }
    
    let mp3 = lame_init()
    lame_set_in_samplerate(mp3, Int32(pcmBuffer.format.sampleRate))
    lame_set_num_channels(mp3, Int32(pcmBuffer.format.channelCount))
    lame_set_out_samplerate(mp3, Int32(pcmBuffer.format.sampleRate))
    lame_set_brate(mp3, 128)
    lame_set_mode(mp3, MONO)
    lame_set_quality(mp3, 2)
    lame_init_params(mp3)
    
    let mp3File = fopen(mp3FilePath, "wb")
    
    let pcmBufferList = UnsafeBufferPointer<AudioBuffer>(start: pcmBuffer.audioBufferList.pointee.mBuffers, count: Int(pcmBuffer.audioBufferList.pointee.mNumberBuffers))
    
    for pcmBuffer in pcmBufferList {
        let samples = pcmBuffer.mData?.assumingMemoryBound(to: Float.self)
        let inputSamples = samples?.withMemoryRebound(to: Int16.self, capacity: Int(pcmBuffer.mDataByteSize) / MemoryLayout<Int16>.size) { $0 }
        
        let outputBuffer = UnsafeMutablePointer<UInt8>.allocate(capacity: 4096)
        let outputBufferPointer = UnsafeMutablePointer<UnsafeMutablePointer<UInt8>?>.allocate(capacity: 1)
        outputBufferPointer.initialize(to: outputBuffer)
        
        let outputBufferSize = lame_encode_buffer(mp3, inputSamples, nil, Int32(pcmBuffer.frameLength), outputBufferPointer, 4096)
        
        let outputData = Data(bytes: outputBuffer, count: Int(outputBufferSize))
        fwrite(outputData.bytes, 1, outputData.count, mp3File)
        
        outputBuffer.deallocate()
        outputBufferPointer.deinitialize(count: 1)
        outputBufferPointer.deallocate()
    }
    
    let outputBuffer = UnsafeMutablePointer<UInt8>.allocate(capacity: 4096)
    let outputBufferPointer = UnsafeMutablePointer<UnsafeMutablePointer<UInt8>?>.allocate(capacity: 1)
    outputBufferPointer.initialize(to: outputBuffer)
    
    let outputBufferSize = lame_encode_flush(mp3, outputBufferPointer, 4096)
    
    let outputData = Data(bytes: outputBuffer, count: Int(outputBufferSize))
    fwrite(outputData.bytes, 1, outputData.count, mp3File)
    
    outputBuffer.deallocate()
    outputBufferPointer.deinitialize(count: 1)
    outputBufferPointer.deallocate()
    
    lame_mp3_tags_fid(mp3, mp3File)
    
    lame_close(mp3)
    fclose(mp3File)
}