如何调用CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer?

问题描述

我试图弄清楚如何在Swift中调用此AVFoundation函数.我花了很多时间摆弄声明和语法，到此为止.编译器通常很高兴，但我还有最后一个难题.

I'm trying to figure out how to call this AVFoundation function in Swift. I've spent a ton of time fiddling with declarations and syntax, and got this far. The compiler is mostly happy, but I'm left with one last quandary.

public func captureOutput(
    captureOutput: AVCaptureOutput!,
    didOutputSampleBuffer sampleBuffer: CMSampleBuffer!,
    fromConnection connection: AVCaptureConnection!
) {
    let samplesInBuffer = CMSampleBufferGetNumSamples(sampleBuffer)
    var audioBufferList: AudioBufferList

    var buffer: Unmanaged<CMBlockBuffer>? = nil

    CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
        sampleBuffer,
        nil,
        &audioBufferList,
        UInt(sizeof(audioBufferList.dynamicType)),
        nil,
        nil,
        UInt32(kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment),
        &buffer
    )

    // do stuff
}

编译器抱怨第三个和第四个参数:

The compiler complains for the 3rd and 4th arguments:

和

那我应该在这里做什么?

So what am I supposed to do here?

我正在使用这个StackOverflow答案，但这是Objective-C.我正在尝试将其翻译成Swift，但是遇到了这个问题.

I'm working off of this StackOverflow answer but it's Objective-C. I'm trying to translate it into Swift, but run into this problem.

还是有更好的方法?我需要一次从缓冲区读取一个样本的数据，所以我基本上是在尝试获取可以迭代的样本数组.

Or is there possibly a better approach? I need to read the data from the buffer, one sample at a time, so I'm basically trying to get an array of the samples that I can iterate over.

推荐答案

免责声明:我刚刚尝试翻译将音频样本读取到Swift，并验证其可以编译.我还没有测试了它是否真的有效.

Disclaimer: I have just tried to translate the code from Reading audio samples via AVAssetReader to Swift, and verified that it compiles. I have nottested if it really works.

// Needs to be initialized somehow, even if we take only the address
var audioBufferList = AudioBufferList(mNumberBuffers: 1,
      mBuffers: AudioBuffer(mNumberChannels: 0, mDataByteSize: 0, mData: nil))

var buffer: Unmanaged<CMBlockBuffer>? = nil

CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(
    sampleBuffer,
    nil,
    &audioBufferList,
    UInt(sizeof(audioBufferList.dynamicType)),
    nil,
    nil,
    UInt32(kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment),
    &buffer
)

// Ensure that the buffer is released automatically.
let buf = buffer!.takeRetainedValue()

// Create UnsafeBufferPointer from the variable length array starting at audioBufferList.mBuffers
let audioBuffers = UnsafeBufferPointer<AudioBuffer>(start: &audioBufferList.mBuffers,
    count: Int(audioBufferList.mNumberBuffers))

for audioBuffer in audioBuffers {
    // Create UnsafeBufferPointer<Int16> from the buffer data pointer
    var samples = UnsafeMutableBufferPointer<Int16>(start: UnsafeMutablePointer(audioBuffer.mData),
        count: Int(audioBuffer.mDataByteSize)/sizeof(Int16))

    for sample in samples {
        // ....
    }
}

这篇关于如何调用CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！