使用getter时UnsafeMutableBufferPointer速度较慢
问题描述:
我有一个带有自定义AURenderCallback的AVAudioEngine。当我运行的引擎,CPU峰值起来,它似乎已经与UnsafeMutableBufferPointer.getter和.setter行动做:使用getter时UnsafeMutableBufferPointer速度较慢
func performRender(ioActionFlags: UnsafeMutablePointer<AudioUnitRenderActionFlags>, inTimeStamp: UnsafePointer<AudioTimeStamp>, inBusNumber: UInt32, inNumberFrames: UInt32, ioData: UnsafeMutablePointer<AudioBufferList>?) -> OSStatus {
let blI = UnsafeMutableAudioBufferListPointer(ioData)
let numSamples = Int((blI?[0].mDataByteSize)!/UInt32(MemoryLayout<Float32>.stride))
for input in 0 ..< blI!.count{
let bI = blI?[input]
guard let inputData = bI?.mData else {
//assert(false)
return kAudioUnitErr_Uninitialized
}
let samplesBI = UnsafeMutablePointer<Float32>(inputData.assumingMemoryBound(to: Float32.self))
let samplesI = UnsafeMutableBufferPointer<Float32>(start: samplesBI, count: numSamples)
for sampleIndex in 0 ..< samplesI.count {
samplesI[sampleIndex] *= 0.5
}
}
return noErr
}
什么会导致获取和设置的这个低效行为指针数据?由于它正在处理音频样本,因此效率低下会导致音频信号中出现断断续续的情况。
答
可以跳过UnsafeMutableBufferPointer()调用,和索引直接样品指针:
let bufferListPtr = UnsafeMutableAudioBufferListPointer(ioData)
...
let mBuffer : AudioBuffer = bufferListPtr[0]
let count = Int(mBuffer.mDataByteSize)/yourSampleSizeInBytes
let dataPointer = UnsafeMutableRawPointer(mBuffer.mData)
if let dptr = dataPointer {
let sampleArray = dptr.assumingMemoryBound(to: yourSampleType.self)
for i in 0..<(count) {
let x = sampleArray[i]
let y = myModifySample(x)
sampleArray[i] = y
}
}
我使用的Int16为mySampleType(大小= 2个字节),但它应该为4个字节的类型浮动工作,以及。
直接使用原始内存指针可能会避免一些缓冲区getter/setter效率低下(也需要验证,所以要小心!)。