Making A DCT in a for loop faster

Hi All,

I need to run a DCT on multiple signals (time slices of the same audio signal).

My current code looks like this:

var ci = Array(stride(from: Float(0), to: Float(y.count), by: Float(p)))

var c = Array<Float>(repeating:0.0, count:y.count)

for (index,value) in ci.enumerated() {

var i = index

var v = Int(value)

var newArray = Array(y[v...(v+Int(p)-1)])

let DCTSetup = vDSP_DCT_CreateSetup(nil, vDSP_Length(newArray.count), vDSP_DCT_Type.II)

var nac = Array<Float>(repeating:0.0, count:newArray.count)

vDSP_DCT_Execute(DCTSetup!, &newArray, &nac)

//c.append(contentsOf: nac)

c.insert(contentsOf: nac, at: v)

}

//c.removeFirst()

But this is taking ages. So for a 10 second audio sample it takes well over 60 seconds.

Is there a way of doing a DCT on multiple signal quickly? (I have made up an array of each sample appended to the other for this computation).

Hope you can help,

Best,

Feras A.