## A DSP Decimation Riddle

Started by in comp.dsp14 years ago 14 replies

Just for fun! When is decimating by N not equivalent to decimating by 2*N followed by interpolating by 2? This is not a trick question and...

Just for fun! When is decimating by N not equivalent to decimating by 2*N followed by interpolating by 2? This is not a trick question and is an actual real-life application. -- % Randy Yates % "Maybe one day I'll feel her cold embrace, %% Fuquay-Varina, NC % and kiss her interface, %%% 919-577-9882 % til then, ...

## Polyphase interpolation followed by decimation, do I get original data?

Started by in comp.dsp15 years ago 6 replies

I am using an 80 tap matched filter to interpolate a signal by 10 times, which splits the coefficients into 10*8taps. After that, I will decimate...

I am using an 80 tap matched filter to interpolate a signal by 10 times, which splits the coefficients into 10*8taps. After that, I will decimate the result by 10 using same filter. Do I get back original data (ignore the delay)?

## Best FIR Coefficients for multirate app

Started by in comp.dsp17 years ago 3 replies

Hello for this newbie question! I'm on developing a simple audio-sequencer application. So, if I want to play a 44100Hz samplesound with a...

Hello for this newbie question! I'm on developing a simple audio-sequencer application. So, if I want to play a 44100Hz samplesound with a default note at D4 like a drum at lower notes like C4,F3,E3,etc., I have to decimate to the according sampling-rate. But of course, to prevent aliasing, there must be a lowpass filter before decimation. The best way to to this very efficient is an FIR-...

## Name That Topology

Started by in comp.dsp12 years ago 9 replies

Hey y'all -- So I've been working with some filter topologies trying to do programmable low-pass filtering over a 100,000:1 Fc range in a...

Hey y'all -- So I've been working with some filter topologies trying to do programmable low-pass filtering over a 100,000:1 Fc range in a single stage, no pre-decimation. (That's unfortunately non-negotiable for reasons above my control). The second order sections that I'm using are basically derived as digital equivalents of analog state variable filters. Flow diagram is: x[n] --> -

## antialiasing and decimation

Started by in comp.dsp16 years ago 4 replies

Hi, is there a way to decimate a signal (reduce sampling rate) reducing aliasing without implementing a computationally intensive...

Hi, is there a way to decimate a signal (reduce sampling rate) reducing aliasing without implementing a computationally intensive low-pass filter? Consider that this signal is supposed to have frequency components higher than the reduced sampling rate. thanks

## Interpolation for Dummies

Started by in comp.dsp18 years ago 14 replies

I am trying to figure out interpolation (I have given up on decimation for now). My scenario is that I have 8 ksamples per second audio (from...

I am trying to figure out interpolation (I have given up on decimation for now). My scenario is that I have 8 ksamples per second audio (from a phone line), and I want to interpolate it to 96 ksamples per second. I know my audio is band limited within 0-4kHz, but other than that it could be anything -- human voice, modem tones, etc. I understand the most basic concepts. I could use lin...

## Decimation/interpolation filters issue when sample rate ratio is variable

Started by in comp.dsp17 years ago 17 replies

Hi fellows, I'm still on my way with the same project, but now, it seems that I'm stuck and need a hint, any pointing into the right...

Hi fellows, I'm still on my way with the same project, but now, it seems that I'm stuck and need a hint, any pointing into the right direction... seems like a brain deadlock which needs an escape... Background: A signal is sampled at 48kS/s. It carries information which is related to a position vector. Since speed is varying, position and time are not proportional, though they are r...

## My first Digital Filter: Can I ask your help?

Started by in comp.dsp11 years ago 13 replies

Hello this is the first time that I approach to DSP so I'm really newbie. I have to write a program that realize a Low Pass Filter at 50...

Hello this is the first time that I approach to DSP so I'm really newbie. I have to write a program that realize a Low Pass Filter at 50 Hz. My processor (ATTINY) have 10bit ADC so for first time I have used Oversampling and Decimation technique for add 3 "Virtual Bit" First Question: Since my Oversampled Frequency is: 4^3 * F-nyquist = 64 * 100 = 6.4KHz ...

## micro DSP with only 8 instructions.

Started by in comp.dsp11 years ago 9 replies

Hello, I am trying to implement a micro DSP with only 8 instruction set. Can you help me with what should be the bare minimum set ...

Hello, I am trying to implement a micro DSP with only 8 instruction set. Can you help me with what should be the bare minimum set required which will cater to most of the applications? FIR, IIR, interpolation, decimation. Forget about FFT for time being, as I am implementing a simple MAC. Maybe even adaptive filtering could be skipped to begin with. ...

## How to do Chroma Decimation

Started by in comp.dsp16 years ago 3 replies

Hi, I am a university student working on a real-time video conferencing project. I'm trying to find a compression solution that will be...

Hi, I am a university student working on a real-time video conferencing project. I'm trying to find a compression solution that will be quick enough to give me the throughput I need, but will also give me the compression ratio I need. Each of my video frames are 320x240 pixels and each pixel has 3 bytes associated with it (R,G,B). For further information, see a post that I made to comp....

## changing sampling rate from 10Ksps to 10.8ksps

Started by in comp.dsp15 years ago 1 reply

Hi All, I need your help in order to find a solution at the following problem: I need to change the sampling rate of a signal from the...

Hi All, I need your help in order to find a solution at the following problem: I need to change the sampling rate of a signal from the original 10ksample per sconds to 10.2 ksps. I should to do this without oversampling and decimation...which other possibilities I have? Ther is a rule that I should apply in all the case where the starting frequency and the final frequency are very clos...

## Is multistage rate-changing actually more efficient?

Started by in comp.dsp12 years ago 10 replies

Hello all, This is a question which probably boils down to "what am I missing?". It seems to be commonly stated that for interpolation or...

Hello all, This is a question which probably boils down to "what am I missing?". It seems to be commonly stated that for interpolation or decimation, it's generally more computationally efficient to perform the operation in multiple stages, i.e. factorise the rate-change factor, and design a lower-order filter for each stage. I completely accept that designing the individual filters in ...

## Sigma Delta Question

Started by in comp.dsp14 years ago 5 replies

I am happy with everything in a SD modulator except the decimation part. You filter then decimate (down-convert the sample rate) and I can see...

I am happy with everything in a SD modulator except the decimation part. You filter then decimate (down-convert the sample rate) and I can see how this gives a bit stream. How to get the other bits though for say a 16 bit word? Or does it not matter ie the bitstream can be taken into a processor in serial form. I always imagine an ADC output as say a 12 bit or more word and not a bitstream wh...

## polyphase filtering

Started by in comp.dsp17 years ago 6 replies

hi.. This is my 1st mail to this group. I am trying to do a polyphase filter bank in dsp and thn get it into FPGA.. this is not for decimation...

hi.. This is my 1st mail to this group. I am trying to do a polyphase filter bank in dsp and thn get it into FPGA.. this is not for decimation or interpolation. This is mainly done for radio telescope back end in which we need 4 or 8 small channels from a big IF coming in. Can any one help me to find wht exactly is polyphase filter. ie whether the filters in the bank is linked with each othe...

## Hogenauer paper

Started by in comp.dsp14 years ago 1 reply

I'm currently designing CIC filters, I found that almost all are referring to the following paper: E=2E B. Hogenauer, =E2=80=9CAn Economical...

I'm currently designing CIC filters, I found that almost all are referring to the following paper: E=2E B. Hogenauer, =E2=80=9CAn Economical Class of Digital Filters for Decimation and Interpolation=E2=80=9D. IEEE Transactions on Acoustics, Speech, and Signal Processing, 29(2):155-162, April 1981. I don't have access to any source for it. Would somebody send it to me by email? Thanks in ...

## Parallel Decimation Filter Implementation?

Started by in comp.dsp14 years ago 1 reply

Hi, I'm hoping that someone out there may be able to help me solve this problem. I'm trying to create a decimate by 2 filter that will have...

Hi, I'm hoping that someone out there may be able to help me solve this problem. I'm trying to create a decimate by 2 filter that will have 4 parallel inputs and 2 outputs. The reason for doing this is that I am receiving data into my FPGA at 4 times the clock FPGAs clock rate. This is being done by bringing in 4 samples per clock. I was thinking of using a polyphase filter, but this...

## Question on channelizer

Started by in comp.dsp9 years ago 11 replies

Hello, I'm a newbie in DSP world and got several questions on channelizer. I recently studied polyphase channelizer and weighted...

Hello, I'm a newbie in DSP world and got several questions on channelizer. I recently studied polyphase channelizer and weighted Overlap-add(WOLA) filter bank. It seems that the only benefit WOLA has is that the number of channels can be not related to the decimation factor. Why is it so beneficial? When each channel is moved to baseband, isn't it desirable to have the minimal sampling freque...

## Interpolation & Decimation

Started by in comp.dsp16 years ago 1 reply

Hello, If a signal is usampled by a factor L & then passed through a filter to interpolate & now I downsample this signal by N where L> N,(or...

Hello, If a signal is usampled by a factor L & then passed through a filter to interpolate & now I downsample this signal by N where L> N,(or decimate), will my resulting signal have an upsampling rate of : L/N ? Will there be any change to the statistics of this signal? If my original signal was gaussian distributed,will the new signal be gaussian distributed too? Looking forward for a reply

## multirate papers

Started by in comp.dsp13 years ago 1 reply

Hello , I`m doing a research for multi-rate technique and i need this 2 very important basic paper that i did not find in web : 1) Croisier,...

Hello , I`m doing a research for multi-rate technique and i need this 2 very important basic paper that i did not find in web : 1) Croisier, A. ,Esteban , D., and Galand "Perfect channel splitting by use of interpolation/decimation/tree decomposition techniques" Int.Symp.on Info.,Circuit and Systems, Patras,Greece, 1976 2)Ramstad,T.A. "analysis/synthesis filter banks with critical samp...

## Polyphase decimation errors

Started by in comp.dsp18 years ago 3 replies

Folks, I understand that, based on the Nobel Identities, the output of a polyphase decimator should be identical to the output of a basic...

Folks, I understand that, based on the Nobel Identities, the output of a polyphase decimator should be identical to the output of a basic FIR decimator. This is due to the fact that even though we decimate in the full input bandwidth all the undersampled aliases will exactly cancel in the final summation. My question is, is this still the case even when we have finite sampling rate and ...