Question

大家好，我是The Amazing Audio Engine和iOS dev的新手，并且一直试图弄清楚如何获得赛道的BPM。

到目前为止，我在论坛上发现了两篇关于离线渲染的文章：

http://forum.theamazingaudioengine.com/discussion/comment/1743/#Comment_1743
http://forum.theamazingaudioengine.com/discussion/comment/649#Comment_649

据我所知，AEAudioControllerRenderMainOutput函数只能在this fork中正确实现。

我正在尝试进行离线渲染以处理曲目，然后使用here（JavaScript）描述的算法并实施here。

到目前为止，我正在加载这个分叉，我正在使用Swift（我现在是Make School Summer Academy的一员，教授Swift）。

播放曲目时，此代码适用于我（无离线渲染！）

let file = NSBundle.mainBundle().URLForResource("track", withExtension: 
"m4a")
let channel: AnyObject! = AEAudioFilePlayer.audioFilePlayerWithURL(file, audioController: audioController, error: nil)


audioController = AEAudioController(audioDescription: AEAudioController.nonInterleavedFloatStereoAudioDescription())

let receiver = AEBlockAudioReceiver { (source, time, frames, audioBufferList) -> Void in

    let leftSamples = UnsafeMutablePointer<Float>(audioBufferList[0].mBuffers.mData)
    // Advance the buffer sizeof(float) * 512
    let rightSamples = UnsafeMutablePointer<Float>(audioBufferList[0].mBuffers.mData) + 512

    println("leftSamples: \(leftSamples) rightSamples: \(rightSamples)")


}

audioController.addChannels([channel])
audioController.addOutputReceiver(receiver)

audioController.start()

尝试离线呈现

这是我在使用this fork

audioController = AEAudioController(audioDescription: AEAudioController.nonInterleaved16BitStereoAudioDescription())

let file = NSBundle.mainBundle().URLForResource("track", withExtension: "mp3")
let channel: AnyObject! = AEAudioFilePlayer.audioFilePlayerWithURL(file, audioController: audioController, error: nil)

audioController.addChannels([channel])
audioController.start(nil)
audioController.stop()

var t = AudioTimeStamp()
let bufferLength: UInt32 = 4096
var buffer = AEAllocateAndInitAudioBufferList(audioController.audioDescription, Int32(bufferLength))
AEAudioControllerRenderMainOutput(audioController, t, bufferLength, buffer)

var renderDuration: NSTimeInterval = channel.duration
var sampleRate: Float64 = audioController.audioDescription.mSampleRate
var lengthInFrames: UInt32 = UInt32(renderDuration * sampleRate)
var songBuffer: [Float64]

t.mFlags = UInt32(kAudioTimeStampSampleTimeValid)
var frequencyAnalyzer = FrequencyAnalyzer()

println("renderDuration \(renderDuration)")

var outIsOpen = Boolean()

AUGraphClose(audioController.audioGraph)

AUGraphIsOpen(audioController.audioGraph, &outIsOpen)

println("AUGraphIsOpen: \(outIsOpen)")

for (var i: UInt32 = 0; i < lengthInFrames; i += bufferLength) {
    AEAudioControllerRenderMainOutput(audioController, t, bufferLength, buffer);
    t.mSampleTime += Float64(bufferLength)

    println(t.mSampleTime)
    let leftSamples = UnsafeMutablePointer<Int16>(buffer[0].mBuffers.mData)
    let rightSamples = UnsafeMutablePointer<Int16>(buffer[0].mBuffers.mData) + 512
    println("leftSamples: \(leftSamples.memory) rightSamples: \(rightSamples.memory)")
}



AEFreeAudioBufferList(buffer)


AUGraphOpen(audioController.audioGraph)
audioController.start(nil)
audioController.stop()

离线渲染对我来说不起作用。第二个例子没有给我带来很多我不理解的混合错误。

一个非常常见的是在这一行的channelAudioProducer函数内：

// Tell mixer/mixer's converter unit to render into audio status = AudioUnitRender(group->converterUnit ? group->converterUnit : group->mixerAudioUnit, arg->ioActionFlags, &arg->originalTimeStamp, 0, *frames, audio);

它给了我EXC_BAD_ACCESS (code=EXC_I386_GPFLT)。除了其他错误之外，这个错误很常见。

对不起，我是这个领域的总菜鸟，但有些东西我真的不懂。我应该使用nonInterleaved16BitStereoAudioDescription还是nonInterleavedFloatStereoAudioDescription？这是如何实现mData的？

我很想得到一些帮助，因为我此刻已经迷失了。请你在回答我的时候尝试尽可能充分地解释它，我是这个人的新手。

注意：如果您不了解Swift，可以在Objective-C中发布代码。

使用Amazing Audio Engine进行离线渲染

0 个答案: