CMSampleBuffer for audio created to be used in unit tests - swift 5.5

CreateSilentAudio.swift

import AVFoundation

func createSilentAudio(startFrm: Int64, nFrames: Int, sampleRate: Float64, numChannels: UInt32) -> CMSampleBuffer {
    let bytesPerFrame = UInt32(2 * numChannels)
    let blockSize = nFrames*Int(bytesPerFrame)
    
    var block: CMBlockBuffer?
    var status = CMBlockBufferCreateWithMemoryBlock(
        allocator: kCFAllocatorDefault,
        memoryBlock: nil,
        blockLength: blockSize,  // blockLength
        blockAllocator: nil,        // blockAllocator
        customBlockSource: nil,        // customBlockSource
        offsetToData: 0,          // offsetToData
        dataLength: blockSize,  // dataLength
        flags: 0,          // flags
        blockBufferOut: &block
    )
    assert(status == kCMBlockBufferNoErr)
    
        // we seem to get zeros from the above, but I can't find it documented. so... memset:
    status = CMBlockBufferFillDataBytes(with: 0, blockBuffer: block!, offsetIntoDestination: 0, dataLength: blockSize)
    assert(status == kCMBlockBufferNoErr)
    
    var asbd = AudioStreamBasicDescription(
        mSampleRate: sampleRate,
        mFormatID: kAudioFormatLinearPCM,
        mFormatFlags: kLinearPCMFormatFlagIsSignedInteger,
        mBytesPerPacket: bytesPerFrame,
        mFramesPerPacket: 1,
        mBytesPerFrame: bytesPerFrame,
        mChannelsPerFrame: numChannels,
        mBitsPerChannel: 16,
        mReserved: 0
    )
    
    var formatDesc: CMAudioFormatDescription?
    status = CMAudioFormatDescriptionCreate(allocator: kCFAllocatorDefault, asbd: &asbd, layoutSize: 0, layout: nil, magicCookieSize: 0, magicCookie: nil, extensions: nil, formatDescriptionOut: &formatDesc)
    assert(status == noErr)
    
    var sampleBuffer: CMSampleBuffer?
    
        // born ready
    status = CMAudioSampleBufferCreateReadyWithPacketDescriptions(
        allocator: kCFAllocatorDefault,
        dataBuffer: block!,      // dataBuffer
        formatDescription: formatDesc!,
        sampleCount: nFrames,    // numSamples
        presentationTimeStamp: CMTimeMake(value: startFrm, timescale: Int32(sampleRate)),    // sbufPTS
        packetDescriptions: nil,        // packetDescriptions
        sampleBufferOut: &sampleBuffer
    )
    assert(status == noErr)
    
    return sampleBuffer!
}

original https://stackoverflow.com/questions/34441648/create-a-silent-audio-cmsamplebufferref but update swift version