Questions tagged [quantization]
The quantization tag has no usage guidance.
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1answer
20 views
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
117 views
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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1answer
205 views
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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41 views
Encoder: Quantization in Frequency Domain
The article, "Let’s build an MP3-decoder!" describes quantization noise in the time domain:
[masking] This property is very useful: not only can the nearby
masked signals be removed; the audible ...
4
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3answers
276 views
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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20 views
Retro Tiled Image Palettization Algorithm?
In most cases today, image palettization consists of reducing the overall number of colors in an image to some fixed number globally. This is typically solved as a straightforward but computationally ...
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2answers
52 views
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 ...
0
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1answer
144 views
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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1answer
216 views
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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2answers
64 views
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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2answers
267 views
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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1answer
31 views
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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2answers
64 views
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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0answers
40 views
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 ...
0
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1answer
56 views
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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1answer
54 views
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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0answers
16 views
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 ...
2
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1answer
105 views
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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0answers
100 views
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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3answers
141 views
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 ...
0
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1answer
55 views
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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0answers
113 views
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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1answer
3k views
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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0answers
53 views
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 ...
1
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1answer
33 views
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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1answer
686 views
how to implement a one 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 go ...
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1answer
211 views
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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1answer
79 views
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 ...
2
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1answer
810 views
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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3answers
604 views
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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2answers
2k views
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 ...
1
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1answer
927 views
Difference between clustering and quantization : Part 2
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 ...
2
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1answer
925 views
Lloyd Max quantization and clustering : Part 1
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 ...
2
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2answers
256 views
DCT: Alternatives to quantization
When using the discrete cosine transform are there commonly used alternatives to quantization to decide which dct components to keep/are important? If not, how do people come up with quantization ...
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1answer
151 views
Proper rounding when converting between digitized values and floating point
I have some very large files that are unsigned 8 bit (0 to 255), real valued. I need to do some simple tuning and decimation. In the past, when I've dealt with low bit rate samples, I've run into ...
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1answer
1k views
Realize Simulink block “Ideal ADC Quantizer” in Matlab
Yesterday I posted following topic: "FFT alternates '0' for a quantized SIN wave".
During post editing I was perturbed by some affair, I didn't formulate correctly the problem. So, my post was blocked ...
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1answer
112 views
Does delta-sigma ADC also reduce Gaussian noise on input signal to ADC or just quantization noise?
The motive for posing this questions arises from a difference of analysis between a colleague an myself.
Our general environment is in the construction of an analog front-end which takes in signals ...
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1answer
66 views
For image quantization, is it necessary to sample image?
When we want to quantize an image, is it necessary to do sampling? When we know that image is a discrete signal, is it necessary to find the best samples with Nyquist rate?
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1answer
453 views
Quantization error in sampling
Consider the analog signal,
$$x(t) = 2\cos(3000\pi t)+3\sin(4000\pi t)+7\cos(6000\pi t)$$
If the sampling rate is 8000 samples per second and quantized at 8 bits, find:
Discrete values at any two ...
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1answer
8k views
Analog to digital conversion using Python
I'm a beginner. I try emulate analog signal conversion to digital (including sampling by time and quantizing by level) using Python. Here is my code:
...
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0answers
98 views
Filter output quantization - does this limit effective coefficient quantization?
I am implementing a filter in hardware, and the intended maximum data input is 16-bit. The question is, if the output is to be re-quantized to 16-bit, does this mean certain coefficients are ...
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1answer
497 views
Help using vector quantization
I have a sample signal, and I computed MFCC using this code.Now I have an array of 1225x12 size, where there are 12 coefficients for 1225 frames. Now I want to test another signal against this sample, ...
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2answers
146 views
Are time series data always contain noise?
I wonder if every time series data should contain noise or not. For example I am taking the price of a ticker, say Yahoo, every hour and noting the values. Does this data contains noise or not?
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1answer
167 views
Quantization SNR of bipolar signal
I want to estimate the SNR of a bipolar signal. I know that each bit increases the SNR at 6 dB. Do i have to subtract one bit for sign, so that for bipolar signals the SNR is (n-1) x 6 dB ?
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2answers
222 views
How does delta modulation work practically?
How does delta modulation work in practice? And where is it used? I find it confusing that, in 1-bit quantization we use only 2 level; if we apply this quantization, there will be loss in information. ...
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0answers
69 views
Dealing with quantization level limiting dsp
There is a analog signal in the form as below:
$$ f(t)=A \sin(\omega(t) t+\phi)+B \sin(\omega(t-t_1) t+\phi_1) $$
Where $$B<<A$$
We are going to calculate $\phi, \phi_1, t_1 $,using dsp. But ...
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1answer
130 views
Cannot understand the attenuation in signal as the audio bit depth of adc changes
I am working on Active Noise Cancellation Project. I came across this strange problem, where the signal is getting attenuated as the audio bit depth changes and I cannot understand it!
My circutit :I ...
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1answer
553 views
Uniform quantizer for gaussian input signal
I have a gaussian signal $x$ with zero mean and unit variance. I am quantizing it by using a uniform quantizer of step size $q$ calculated by
$$q = \frac{x_\mathrm{max} - x_\mathrm{min}}{2^{M_\mathrm{...
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1answer
340 views
What is “hard quantization” strategy?
I am working on classification and several times I encountered with this term.
What is hard quantization strategy?
What does it differ from soft approach?
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2answers
84 views
Why are vector quantizers not used in video codecs?
Using a vector quantizer (VQ), groups of image samples (or motion compensated and/or transformed data) can be quantized as vectors. I'm curious about why VQs are not preferred in the modern, highly ...
