Questions tagged [quantization]

Quantization, in mathematics and digital signal processing, is the process of mapping input values from a large set (often a continuous set) to output values in a (countable) smaller set, often with a finite number of elements. Rounding and truncation are typical examples of quantization processes.

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Is there a common adaptive image color quantization (posterization) method?

I know there are a lot of methods to quantize colors in an image given a number of colors. For example the k-mean algorithm enables to reduce the number to k colors. I'm looking for an adaptive method ...
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Binary image? Only black and white? [closed]

By name, a binary image is one that has two levels. But is it essential that those two colors are black and white? Or any other combination also allowed as shown in attached snap. Snap is output image,...
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Fixed Point Design Resources

Can anyone point me to good methodologies for designing fixed point versions of possibly nonlinear signal processing algorithms? Are there any systematic methods other than simulation for optimizing ...
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What's the difference between quantization and coding?

From what I understand quantization takes an analog signal and assigns numerical values to it as convert it to a discrete signal. However coding converts a signal into binary. It seems like coding is ...
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Explanation for the quantization matlab function

I found this code on quantization on page 314 in the book Modern Digital and Analog Communication Systems by B.P.Lathi and Zhi Ding. I can understand only half of the code. Please, someone, help in ...
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QPSK matlab/simulink Quantisation effects

I am trying to simulate the effects of quantization of an ADC on different waveforms (e.g. QPSK,8PSK) in Simulink. For the case of QPSK the default BER curve would be generated with 2 bits per symbol ...
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Difference between formula of SNR and SQNR?

Is there any difference between formula/expressionsof SNR and SQNR? where SNR is Signal to noise ratio and SQNR is signal to quantization noise . The following DSP SE question shows both SNR and SQNR ...
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How we can quantize a sampled signal in MATLAB?

I have a continuous time signal $x(t)=\sin(2πft)$ where $0 \leq t \leq 3$. I want to sample the continuous time signal and then quantize that sampled signal and then plot both sampled and quantized ...
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How to find the sampling vector of HD camera recording?

An HD camera records 1080p video (1080*1920, prograssive, 30 frames/sec) wiht croma subsampling 4:2:0 for a total of 90 minutes. The quantizer which is being used for the chroma representation has 256 ...
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How to calculate SNR of dead-band quantizer?

Suppose we have a dead-band quantizer with $\ N = 5 \ quantizing \ levels $ which uses $\ b = 3 \ bits $ for each produced symbol. The quantizer gets as input a uniformly distributed signal $\ X $ ...
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confusion sampling vs quantization?

while converting analog signal to digital equivalent,we have a process that is called analog to digital conversion and it has two main steps/stages sampling and quantization? I am confused whether y ...
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Why are we always interested in mean-squared distortion?

When dealing with quantizers, and in many other communications problems, the interest is usually on the mean-squared distortion or mean-squared error, rather than mean absolute error or anything else. ...
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Variance of a signal

How to calculate the variance of noise samples modeled as follows: $n_a(t)$ is a Gaussian zero-mean white noise process with (two-sided) power spectral density $\frac{N_0}{2}$. $n_a(t)$ is passed ...
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Sample & Hold: Estimate jitter delay of an ADC

I've got a question regarding the effects of sample and hold. My input signal is $x$, and my output signal $x_{SH}$. The error between the signals is $e_{SH} = x_{SH}-x$. The sampling frequency is ...
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Is there any difference in Implementing sigma delta modulator using filters and state space model in FPGA?

Sigma delta modulation is extensively used in quantization to reduce quantization noise. In the literature one can see different architecture for example python-deltasigma to implement a modulator. ...
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Signal to Quantization noise problem

a full scale signal of bandwidth 5 khz is sampled by an 10-bit ADC at a sampling rate of 2 Msa/sec calculate the Signal to Quantization noise of the resulting DT signal repeat for a 14-bit ADC at ...
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Novice question about mid-rise quantization

Accoarding to wikipage, the function for quantization has the ceiling of x/Ds. Is this the ceiling of something multiplied by Ds?
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How good is the Leech lattice for AWGN coding or MSE quantization of Gaussian sources?

Anyone know where to find graphs showing how well it works vs other schemes? thanks
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Quantization step-size for a given signal based on its PDF

I am familiar with the principles of midtread and midrise quantizer. However, I have difficulties determining the step size where it hasn't been explicitly given. For example, the following ...
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Separability vs. Resolution - Synonymous terms?

In terms of discrete representation of a variable, let's say time measurements in absolute values in [seconds], is there a difference between separability and resolution? When do speak of either ...
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Differential Pulse Code Modulation (DPCM)

In the following figure we see an encoder and a decoder of a Delta Modulation System, which is a simple DPCM System with a 1-bit quantizer: We assume that signal $x(n)$ is known, that $\hat{x}(-1)=0$ ...
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Optimal amplitude of an $m$-bit sinusoid

A continuous-time sinusoid of zero-to-peak real amplitude $A \le 2^{m-1}-0.5$ (e.g., for $m=16$, $A \le 32767.5$) is quantized to $m$-bit resolution by rounding it to the nearest integer (Fig. 1). ...
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Precise 5th and 7th harmonics of a sampled sine wave

Does anyone know in decibels (to 1/100th of a dB) what the theoretical 3rd, 5th and 7th harmonic of a 0dB fs 24-bit (i.e. full-level; 0dB = -8,388,607 to 8,388,607) sampled sine wave without dither ...
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JPEG compression steps after quantization

I have a 3-channel (for colours) a png image that I opened and I splitted the image into 8x8 blocks I applied all of the blocks discrete cosine transform And then applied quantization I stored the ...
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How to determine a quantization table for image compression with DCT?

The quantization table is given on the JPEG Wiki page. How was this table derived? I'm currently doing a project where I have to come up with custom quantization table for an image, but I don't know ...
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Why use a 1-bit ADC in a Sigma Delta Modulator?

When looking at the discrete model of a Sigma-Delta Modulator as shown below, we can see that the quantizer is modelled as a white-noise source $e[n]$. From this model, we can derive the noise shaping ...
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Why is distorted / quantized white noise still white noise?

White noise can be created by setting every sample in the time domain to a random number with a gaussian distribution. Every sample is random, so the frequency response is obviously random. Easy ...
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Quantization level versus bandwidth [closed]

Why is it that increasing the number of quantization levels $L$ results in an increase in the signal's bandwidth?
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THD requirement for generated sine

I need to generate a sine signal using a DAC with a certain THD specification, say 0.1% @ 1KHz. As a first approach I’m considering it to be an ideal DAC along with an ideal LPF for aliasing removal ...
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What distribution is the easiest to compress?

I'm currently playing around with some compression algorithms and I'm asking myself if there is a type of data distribution / noise distribution that is easier to target with quantization (meaning ...
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What is wrong with my 3D DCT quantization?

I'm implementing 3D DCT quantization as in Quantization of 3D-DCT Coefficients and Scan Order for Video Compression (sorry about the paywall). They propose the following equation for generating the ...
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Harmonics in Quantal Histogram

I'm studying what I believe to be a system that produces a (noisy) quantal response (i.e. there should be a minimum increment of response). To do this, I've plotted a histogram of some ~6000 amplitude ...
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What information does the abs(normalized_image - normalized_quantised_image) carry?

Given a grayscale image X2 And its (under)quantised version with 3 bits depth X3 What information does the abs(X2_normalized - X3_normalized) carry?As an example ...
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Quantization of Image which have taken from partially less dark

I have picture with high resolution with 20M memory space and this image has been taken from the standing away from the window in room which has significantly less light as compared to outside. Image ...
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Why harmonic components appear only after a certain level when a signal is clipped?

I recently observed this phenomenon that when a signal is clipped the harmonics start to appear only after a certain level. The Python code to reproduce the effect is given below. The signal has 3 ...
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How much will a low/high pass filter reintroduce quantization noise into a dithered signal?

For example, most audio signals are dithered prior to distribution. However, if a low or high pass filter is introduced after dithering or during playback, won't that negate some of the benefits of ...
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Is the incoming sample in a standard DPCM already quantized?

I began learning about DPCM and i've got one issue I am not sure about: Is the incoming sample m[k] (see image for reference) already quantizied or not? I think it is but with an (assumed) very fine ...
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Correct way to quantize accelerometer data with microsecond precision?

I am analyzing large volumes of raw accelerometer data (~12 hours @ 200Hz) using Python. Some calculations (e.g. deriving Jerk) necessitate a time index with a regular interval. I have microsecond-...
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Which type of quantization is better?

If a signal's amplitude has a uniform PDF, which is better in the sense of producing a smaller quantization error: optimal scalar quantization or quantization with compressor (non-uniform quantization)...
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Compute SQNR (Signal to Quantization Noise Ratio)

I'm studying the quantization of an audio signal and in particular the SQNR (Signal to Quantization Noise Ratio). The book on which the study says that: where: N is the number of bits in the ...
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Modelling of quantization noise with logarithmic steps

I have to modell the quantization noise of ADC. I only know that the maximum relative error is 1 dB. Since this is logarithmic, I find it hard to formulate an appropriate model for the quantization ...
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Is it necessary to scale a signal for quantization noise analysis?

I am doing a series of tests to analyse the round-off (quantization) noise performance of single and two stage biquad cascades (direct form 1), at different sampling rates. The system I am simulating ...
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How to implement a $1$-bit quantizer in Simulink?

I am trying to implement a delta-sigma modulator block diagram in Matlab Simulink but can't find a $1$-bit quantizer (which is required in the modulator) anywhere. Could anyone please tell me how to ...
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What is the no overload region of a quantizer?

I was watching a video on quantization noise and the instructor kept referring to the "no overload" region of a quantizer? Could anyone please explain what that term means?
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Is there any literature discussing PDF after quantization?

Consider a random variable with a known distribution. I want to know if we quantized the variable the how the probability density function(PDF) would change? Specifically if the original PDF is ...
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How to Reverse Color Quantization?

Are there any algorithms that attempt to perform the inverse of color quantization on an image? In other words, is there a smart way to increase the bit depth of image? The obvious answer would be to ...
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Signal to Quantization Noise Ratio (SQNR)

I have this problem in my homework (following picture). How do find the signal to quantization noise ratio at the output? I don't want the solution. I just want to know a better approach to tackle ...
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why does quantisation noise sound like white noise?

To record sound and transform it to digital form, audio signals are recorded and its pressure levels are sampled and quantised. Why does quantisation noise sound like white noise?
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A query on the non-uniform quantization

I have read that non-uniform quantization boosts the smaller amplitude signals by a large amount. However the larger amplitude signals receive a small gain. As shown in the below diagram (Compressor ...
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What is the difference between clustering and quantization?

The Lloyd-Max quantizer is a scalar quantizer which can be seen as a special case of a vector quantizer (VQ) designed with the Linde Buzo Gray (LBG) algorithm. In k-means clustering, we are given a ...