FloatToSampleBufferToFloat.swift

import UIKit
import AVFoundation

public func createSampleBufferBy<T>(pcm: [T], timeStamp: AudioTimeStamp, bd: AudioStreamBasicDescription) -> CMSampleBuffer? {
    var basicDescription = bd
    var formatDescription: CMAudioFormatDescription?
    _ = CMAudioFormatDescriptionCreate(allocator: kCFAllocatorDefault,
                                                asbd: &basicDescription,
                                                layoutSize: 0,
                                                layout: nil,
                                                magicCookieSize: 0,
                                                magicCookie: nil,
                                                extensions: nil,
                                                formatDescriptionOut: &formatDescription)
    var blockBuffer: CMBlockBuffer?
    _ = CMBlockBufferCreateWithMemoryBlock(allocator: kCFAllocatorDefault,
                                           memoryBlock: UnsafeMutableRawPointer(mutating: pcm),
                                           blockLength: pcm.count * MemoryLayout<T>.stride,
                                           blockAllocator: kCFAllocatorNull,
                                           customBlockSource: nil,
                                           offsetToData: 0,
                                           dataLength: pcm.count * MemoryLayout<T>.stride,
                                           flags: 0,
                                           blockBufferOut: &blockBuffer)
    var sampleBuffer: CMSampleBuffer?
    
    let t = CMTime(value: CMTimeValue(Int(AVAudioTime.seconds(forHostTime: mach_absolute_time()) * 1000000000)),
                   timescale: 1000000000,
                   flags: .init(rawValue: 3),
                   epoch: 0)
    _ = CMAudioSampleBufferCreateWithPacketDescriptions(allocator: kCFAllocatorDefault,
                                                        dataBuffer: blockBuffer,
                                                        dataReady: true,
                                                        makeDataReadyCallback: nil,
                                                        refcon: nil,
                                                        formatDescription: formatDescription!,
                                                        sampleCount: pcm.count,
                                                        presentationTimeStamp: t,
                                                        packetDescriptions: nil,
                                                        sampleBufferOut: &sampleBuffer)
    return sampleBuffer
}

extension AudioBufferList {
    public mutating func convert() -> [AudioBuffer] {
        let buf: UnsafeBufferPointer<AudioBuffer> = UnsafeBufferPointer<AudioBuffer>(start: &(self.mBuffers), count: Int(self.mNumberBuffers))
        return Array(buf)
    }
}

extension AudioBuffer {
    public func convert() -> [Float] {
        if let mdata = self.mData {
            let ump = mdata.bindMemory(to: Float.self, capacity: Int(mDataByteSize))
            let usp = UnsafeBufferPointer(start: ump, count: Int(mDataByteSize) / MemoryLayout<Float>.size)
            return [Float](usp)
        } else {
            return []
        }
    }
}

let basicDescription = AudioStreamBasicDescription(mSampleRate: 48000,
                                                   mFormatID: kAudioFormatLinearPCM,
                                                   mFormatFlags: kLinearPCMFormatFlagIsFloat,
                                                   mBytesPerPacket: 4,
                                                   mFramesPerPacket: 1,
                                                   mBytesPerFrame: 4,
                                                   mChannelsPerFrame: 1,
                                                   mBitsPerChannel: 32,
                                                   mReserved: 0)

let pcm = { () -> [Float] in
    var samples: [Float] = []
    for n in 0..<1024 {
        samples.append(sinf(Float(2.0 * Double.pi) * 440 * Float(n) / 44100))
    }
    return samples
}()


let sampleBuffer = createSampleBufferBy(pcm: pcm, timeStamp: AudioTimeStamp(mSampleTime: 0, mHostTime: 0, mRateScalar: 0, mWordClockTime: 0, mSMPTETime: .init(), mFlags: .init(rawValue: 0), mReserved: 0), bd: basicDescription)

var audioBufferList = AudioBufferList(mNumberBuffers: 1, mBuffers: AudioBuffer(mNumberChannels: 0, mDataByteSize: 0, mData: nil))
var blockBuffer: CMBlockBuffer?
_ = CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer!,
                                                            bufferListSizeNeededOut: nil,
                                                            bufferListOut: &audioBufferList,
                                                            bufferListSize: MemoryLayout<AudioBufferList>.stride,
                                                            blockBufferAllocator: nil,
                                                            blockBufferMemoryAllocator: nil,
                                                            flags: kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment,
                                                            blockBufferOut: &blockBuffer)
print(blockBuffer)
print(audioBufferList)

print(pcm)
print("\n")
print(audioBufferList.convert()[0].convert())