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Questions tagged [vdsp]

vDSP is the (vector) digital signal processing portion of Apple’s Accelerate framework.

vDSP is the (vector) digital signal processing portion of Apple’s Accelerate framework, part of OS X and iOS. It provides a variety of vector and array functions for signal processing and other applications. vDSP uses hardware features such as SIMD (Single Instruction Multiple Data) to provide high performance.

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vDSP fft computation good practice

In order to compute the FFT with Accelerate framework, I see a lot of people using (the old way I guess) fft_zrip instead of the recommended one by Apple in the vDSP documentation ​DSP_DFT_Execute. Is there any reason why ​DSP_DFT_Execute is so…
DEADBEEF
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Vector Accelerated Euclidean Distance in 3D

I am in need of performing a very common and simple matrix operation. However I need it fast, really fast... I am already considering a multi-threaded implementation, however for now I just want to see how fast I can get it on a single…
Luigi Castelli
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Convert decibels to volume using Accelerate Framework

I am building some kind of an audio fader effect. I am using vDSP_vdbcon to turn a buffer of volumes into decibels, applying some modifications in db-space and would like to convert the decibel buffer into volume using the accelerate…
Florian Doyon
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Linear resampling datapoints captured at fluctuating time intervals, to flxed time intervals, in swift

I want to linearly interpolate some metrics that are captured at times that fluctuate, to fixed timing intervals. let original_times:[Double] = [0.0,1.3,2.2,3.4,4.2,5.5,6.6,7.2,8.4,9.5,10.0] let metric_1:[Double] = [4,3,6,7,4,5,7,4,2,7,2] let…
Ian
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Swift vDSP_create_fftsetup deprecated in iOS 8.4?

I am using some FFT routine I wrote for another application in Swift a couple of months ago. The line initializing the FFT setup, i.e. calculating the weights of the FFT, let fft_weights: FFTSetup = vDSP_create_fftsetup(17,…
Bertrand Delvaux
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Objective-C: Cross correlation of two audio files

I want to perform a cross-correlation of two audio files (which are actually NSData objects). I found a vDSP_convD function in accelerate framework. NSData has a property bytes which returns a pointer to an array of voids - that is the parameter of…
Patrik Vaberer
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Accelerate framework used, no observable speedup

I have the following piece of audio code that I thought would be a good candidate for using vDSP in accelerate framework. // --- get pointers for buffer lists float* left = (float*)audio->mBuffers[0].mData; float* right = numChans == 2 ?…
lppier
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Can the Accelerate Framework aggregate array values based on a separate index array?

I am trying to determine if the Accelerate Framework can help speed up a calculation my app has to perform. Let's say I have the following arrays: invoice[0..n], an array of doubles containing invoice values week[0..n], an array of integers, where…
Eduardo
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Bandpass filter audio recording using Accelerate framework (vDSP) and Novocaine

I'm fairly new to signal processing, so please bear with me. I'm trying to implement a bandpass filter to apply to an audio recording obtained from an iPad. The recording has been converted to a Float32 pointer using ExtFile functions and…
user3489828
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OpenCL slow -- not sure why

I'm teaching myself OpenCL by trying to optimize the mpeg4dst reference audio encoder. I achieved a 3x speedup by using vector instructions on CPU but I figured the GPU could probably do better. I'm focusing on computing auto-correlation vectors in…
Tim
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Accelerate framework vDSP, FFT framing

I'm trying to implement FFT calculation, using Apple's vDSP, on a recorded audio file (let's assume it's a mono PCM). I've did a research here and I've found following topics quite useful: Using the apple FFT and accelerate Framework Extracting…
Dmytro Kabyshev
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vDSP_desamp FIR filter sample history continuity

I'm trying to use the vDSP_desamp() routine to perform downsampling of an audio signal that is being constantly captured. According to the Accelerate-framework documentation, this routine performs FIR filtering and decimation. However I have a…
user1222021
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iPhone Accelerate Framework FFT to convert a two-dimensional array

I'm working on a project that requires a Fourier transform of a 2D array. However, I'm far from being an expert with both FFT's or particularly vDSP. I've seen some examples here, here or here but they are either for 1D arrays or I can't quite…
dwbrito
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What actually does the size of FFT mean

While using FFT sample code from Apple documentation, what actually does the N, log2n, n and nOver2 mean? Does N refer to the window size of the fft or the whole number of samples in a given audio, and how do I calculate N from an audio file? how…
Firdous
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Convolution function vDSP_imgfir returning 0 values

I am trying to use Accelerate framework on iphone (iOS 5.1) in order to do matrix convolution. However, when I run the function double *dst = calloc(2*3,sizeof(double)); double…
kahlo
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