Load a Pcm into a Avaudiopcmbuffer

load a pcm into a AVAudioPCMBuffer

Thanks to Rhythmic Fistman in the comments, I went and loaded it myself, that way:

func loadSoundfont(_ pitch : String) {
    let path: String = Bundle.main.path(forResource: "\(self.id)/\(pitch)", ofType: "f32")!
    let url = URL(fileURLWithPath: path)

    do {
        let data = try Data(contentsOf: url)
        let format = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 2, interleaved: true)

        self.buffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: AVAudioFrameCount(data.count))

        self.buffer!.floatChannelData!.pointee.withMemoryRebound(to: UInt8.self, capacity: data.count) {
            let stream = OutputStream(toBuffer: $0, capacity: data.count)
            stream.open()
            _ = data.withUnsafeBytes {
                stream.write($0, maxLength: data.count)
            }
            stream.close()
        }

    } catch let error as NSError {
        print("ERROR HERE", error.localizedDescription)
    }
}

Convert audio into raw PCM data of type [Double]

But AVAudioFormat does know .PCMFormatFloat64:

let format = AVAudioFormat(commonFormat: .PCMFormatFloat64, sampleRate: file.fileFormat.sampleRate, channels: 1, interleaved: false)

Maybe you mean AVAudioPCMBuffer doesn't have a float64ChannelData convenience property?

That's fine, you can use AVAudioPCMBuffer's superclass, AVAudioBuffer has everying you need to be able to get at the raw Double/Float64 samples:

let abl = buf.audioBufferList.memory
let doubles = UnsafePointer<Double>(abl.mBuffers.mData)
doubles[0] // etc...

In full:

let file = try! AVAudioFile(forReading: self.soundFileURL)
let format = AVAudioFormat(commonFormat: .PCMFormatFloat64, sampleRate: file.fileFormat.sampleRate, channels: 1, interleaved: false)

let buf = AVAudioPCMBuffer(PCMFormat: format, frameCapacity: UInt32(file.length))
try! file.readIntoBuffer(buf)
let abl = buf.audioBufferList.memory
let doubles = UnsafePointer<Float64>(abl.mBuffers.mData)

How can mp3 data in memory be loaded into an AVAudioPCMBuffer in Swift?

I went down the rabbit hole on this one. Here is what probably amounts to a Rube Goldberg-esque solution:

A lot of the pain comes from using C from Swift.

func data_AudioFile_ReadProc(_ inClientData: UnsafeMutableRawPointer, _ inPosition: Int64, _ requestCount: UInt32, _ buffer: UnsafeMutableRawPointer, _ actualCount: UnsafeMutablePointer<UInt32>) -> OSStatus {
    let data = inClientData.assumingMemoryBound(to: Data.self).pointee
    let bufferPointer = UnsafeMutableRawBufferPointer(start: buffer, count: Int(requestCount))
    let copied = data.copyBytes(to: bufferPointer, from: Int(inPosition) ..< Int(inPosition) + Int(requestCount))
    actualCount.pointee = UInt32(copied)
    return noErr
}

func data_AudioFile_GetSizeProc(_ inClientData: UnsafeMutableRawPointer) -> Int64 {
    let data = inClientData.assumingMemoryBound(to: Data.self).pointee
    return Int64(data.count)
}

extension Data {
    func convertedTo(_ format: AVAudioFormat) -> AVAudioPCMBuffer? {
        var data = self

        var af: AudioFileID? = nil
        var status = AudioFileOpenWithCallbacks(&data, data_AudioFile_ReadProc, nil, data_AudioFile_GetSizeProc(_:), nil, 0, &af)
        guard status == noErr, af != nil else {
            return nil
        }

        defer {
            AudioFileClose(af!)
        }

        var eaf: ExtAudioFileRef? = nil
        status = ExtAudioFileWrapAudioFileID(af!, false, &eaf)
        guard status == noErr, eaf != nil else {
            return nil
        }

        defer {
            ExtAudioFileDispose(eaf!)
        }

        var clientFormat = format.streamDescription.pointee
        status = ExtAudioFileSetProperty(eaf!, kExtAudioFileProperty_ClientDataFormat, UInt32(MemoryLayout.size(ofValue: clientFormat)), &clientFormat)
        guard status == noErr else {
            return nil
        }

        if let channelLayout = format.channelLayout {
            var clientChannelLayout = channelLayout.layout.pointee
            status = ExtAudioFileSetProperty(eaf!, kExtAudioFileProperty_ClientChannelLayout, UInt32(MemoryLayout.size(ofValue: clientChannelLayout)), &clientChannelLayout)
            guard status == noErr else {
                return nil
            }
        }

        var frameLength: Int64 = 0
        var propertySize: UInt32 = UInt32(MemoryLayout.size(ofValue: frameLength))
        status = ExtAudioFileGetProperty(eaf!, kExtAudioFileProperty_FileLengthFrames, &propertySize, &frameLength)
        guard status == noErr else {
            return nil
        }

        guard let pcmBuffer = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: AVAudioFrameCount(frameLength)) else {
            return nil
        }

        let bufferSizeFrames = 512
        let bufferSizeBytes = Int(format.streamDescription.pointee.mBytesPerFrame) * bufferSizeFrames
        let numBuffers = format.isInterleaved ? 1 : Int(format.channelCount)
        let numInterleavedChannels = format.isInterleaved ? Int(format.channelCount) : 1
        let audioBufferList = AudioBufferList.allocate(maximumBuffers: numBuffers)
        for i in 0 ..< numBuffers {
            audioBufferList[i] = AudioBuffer(mNumberChannels: UInt32(numInterleavedChannels), mDataByteSize: UInt32(bufferSizeBytes), mData: malloc(bufferSizeBytes))
        }

        defer {
            for buffer in audioBufferList {
                free(buffer.mData)
            }
            free(audioBufferList.unsafeMutablePointer)
        }

        while true {
            var frameCount: UInt32 = UInt32(bufferSizeFrames)
            status = ExtAudioFileRead(eaf!, &frameCount, audioBufferList.unsafeMutablePointer)
            guard status == noErr else {
                return nil
            }

            if frameCount == 0 {
                break
            }

            let src = audioBufferList
            let dst = UnsafeMutableAudioBufferListPointer(pcmBuffer.mutableAudioBufferList)

            if src.count != dst.count {
                return nil
            }

            for i in 0 ..< src.count {
                let srcBuf = src[i]
                let dstBuf = dst[i]
                memcpy(dstBuf.mData?.advanced(by: Int(dstBuf.mDataByteSize)), srcBuf.mData, Int(srcBuf.mDataByteSize))
            }

            pcmBuffer.frameLength += frameCount
        }

        return pcmBuffer
    }
}

A more robust solution would probably read the sample rate and channel count and give the option to preserve them.

Tested using:

let url = URL(fileURLWithPath: "/tmp/test.mp3")
let data = try! Data(contentsOf: url)

let format = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: 44100, channels: 1, interleaved: false)!
if let d = data.convertedTo(format) {
    let avf = try! AVAudioFile(forWriting: URL(fileURLWithPath: "/tmp/foo.wav"), settings: format.settings, commonFormat: format.commonFormat, interleaved: format.isInterleaved)
    try! avf.write(from: d)
}

How can I to resize PCM audio sample buffer longer?

Usually linear interpolation works. What is the bit-resolution of your PCM file? If it is 16 bits (pretty typical), you'll have to first convert two bytes into a single value before applying the interpolation, and then disassemble the values back to bytes. You will need to know the byte order, as it can be either little-endian or big-endian.

EDIT: I should have added that the pitch will drop with this method of lengthening the file, unless the playback frame rate increases. To stretch out a sound in time without affecting its pitch is considerably more complicated.

Getting AVAudioPCMBuffer working (AVAudioFile.mm error code -50)

The AVAudioPCMBuffer's PCMFormat has to be set as the AVAudioFile's .processingFormat and not its .fileFormat: I thought these were the same, but that's not the case!

-50 error when converting PCM buffer with AVAudioConverter

An Apple engineer answered this on their dev forums. I missed that the convert(to:from:) variant of AVAudioConverter can't convert sample rate so you have to use the withInputFrom variant. The docs on that aren't too clear but I came up with:

private func pcmBufferForFile(filename: String, sampleRate: Float) -> AVAudioPCMBuffer {

    guard let newFormat = AVAudioFormat(standardFormatWithSampleRate: Double(sampleRate), channels: 1) else {
        preconditionFailure()
    }
    guard let url = Bundle.main.url(forResource: filename, withExtension: "wav") else {
        preconditionFailure()
    }
    guard let audioFile = try? AVAudioFile(forReading: url) else {
        preconditionFailure()
    }
    guard let tempBuffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat,
                                            frameCapacity: AVAudioFrameCount(audioFile.length)) else {
        preconditionFailure()
    }

    let conversionRatio = sampleRate / Float(tempBuffer.format.sampleRate)
    let newLength = Float(audioFile.length) * conversionRatio
    guard let newBuffer = AVAudioPCMBuffer(pcmFormat: newFormat,
                                           frameCapacity: AVAudioFrameCount(newLength)) else {
        preconditionFailure()
    }

    do { try audioFile.read(into: tempBuffer) } catch {
        preconditionFailure()
    }
    guard let converter = AVAudioConverter(from: audioFile.processingFormat, to: newFormat) else {
        preconditionFailure()
    }
    var error: NSError?
    converter.convert(to: newBuffer, error: &error, withInputFrom: { (packetCount, statusPtr) -> AVAudioBuffer? in
        statusPtr.pointee = .haveData
        return tempBuffer
    })
    if error != nil {
        print("*** Conversion error: \(error!)")
    }
    return newBuffer
}

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