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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Selective JPEG compression
note: my question is not answered here: Selective image compression? - I couldn't find it, I looked for "selective" and "adaptive" compression, maybe, I put the search query ...
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How to measure correlation between 1 bit samples and theoretical original waveform?
I'm investigating quantization error.
I have an analogue waveform that looks like this and is of theoretically infinite resolution:-
I've sampled it as (8 bit oscilloscope readings & 0b1) to ...
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Spectral Property of Bandlimited Quantized Signal
recently I meet a problem.
I generate a random Gaussian signal $x$ with mean $0$ in MATLAB. And use a $4$th lowpass Butterworth filter to acquire $x'$. Then I use the binary rounding quantization ...
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Is there an optimal way to quantize log-likelihood ratios of an AWGN channel?
My understanding is that given an AWGN channel and BPSK modulation, an LDPC decoder that uses message passing takes as input log-likelihood ratios $L$ of the following form by Bayes' rule:
$$
L=\frac{...
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Oversampling in quantization
Q: It is said that "to maintain the same quality in the two cases, we require that the power spectral densities remain the same". Why is this a measure of the same quality? Why is not
the ...
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Connection between SNR and the dynamic range of the human ear
For signal-to-noise ratio (SNR), SNR=6B dB is called the dynamic range of
the quantizer.
The dynamic range of the 16-bit quantizer is 6B = 6·16 = 96 dB. Note that the dynamic range of
the human ear ...
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Unclear point about quantization
Quantization of Continuous-Amplitude Signals
This point is not clear to me:
"The smallest quantization levels ($\pm\Delta$) correspond to the least significant bit of the binary code word."...
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Non-Uniform Quantization
I was reading a research paper on companding schemes for non uniform quantisation. In paper one of the motivations for non-uniform quantisation is that distortion at larger amplitude values is less ...
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1answer
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Quantization and Sampling - putting it all together
So after I learned this two topic: quantization and sampling, I'm learning the way to look at both of them and try to optimize the split of a given amount of bit B to N and k, where N is the amount of ...
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Help in LBG Vector Quantization - Splitting Factor
I'm currently making a program for speech recognition. In the step of codebook generation using the LBG (Linde-Buzo-Gray) algorithm, I've read that the splitting factor $\varepsilon = 0.01$ (generally)...
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Quantization types
Suppose i have input sequence
{-1.3,1.2,-0.2,-0.5,0.4,0.89,1.3}
Which are uniformly quantized through a quantizer having range (-1.5,1.5) with 4 levels
My calculted answers for-
First method:mid rise ...
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SNR of μ-law companding
I know the snr after μ-law compression is
$\text{SNR}\approx\frac{3L^2}{[\ln(1+ \mu)]^2}$
when $\mu \gg \frac{\max_t m(t)}{\text{rms}(m(t))}$,
where $m(t)$ is the message signal, and
$L$ the number ...
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Quantization SNR of sine wave doesn't match 1.761 + 6.02 * Q
I am trying to show with numpy that the quantization noise of a sine wave matches the SNR formula of SNR = 1.761 + 6.02 * Q.
The numpy code is simple:
...
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1answer
120 views
How to quantize filter coefficients to 10 bits
I am trying to learn digital filter design. One of the concept is quantization of filter coefficients. I used Designfilt to design an lowpass IIR filter and obtained coefficients. Now I want to ...
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2answers
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Having converted a grayscale image to binary using `im2bw()`, is the converse operation possible?
I have converted a gray-scale image to binary using im2bw() now i wanna do the opposite. How can I do that in MATLAB?
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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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1answer
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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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1answer
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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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1answer
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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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1answer
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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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1answer
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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 ...
