A magnitude of the sampled image is expressed as a digital value in image processing. If the original spectrum would have looked either one of the gray blocks, the resulting recon. Introduction the purpose of this lab is for you to understand the principles of sampling a continuous time signal, increasing or decreasing the sampling rate of a discrete time signal, and for quantization. Compute the new quantization levels as the mean of the value of all points assigned to each quantization level. Quantization we measure discrete amplitudes in bits. So if youre doing that kind of a quantization scheme, then the thing you have to think about is how many bits. The basic idea behind converting an analog signal to its digital signal is. That is, it is generated by the process of sampling and quantization described in section 5. We will discuss sampling now, and quantization will be discussed later on but for now on we will discuss just a little about the difference between these two and the need of these two steps.
Lecture 11 data converters sampling, aliasing, reconstruction amplitude quantization. Wav, aiff, au, raw, and pcm files can store uncompressed audio data. A note on the tradeoff between sampling and quantization. Pdf understanding the sampling process researchgate. The first box, the sampling box, takes the ct signal of time and turns it into a dt signal. Sample and hold timing and electrical diagram after the sampling time, the input capacitor has the same voltage as the input, the analog switch is then disconnected from the input and successive approximation conversion is started, to convert the voltage stored in the hold capacitor. An 8bit sample breaks the sound wave into 255 increments compared with 65,535 for a 16bit. This is the sampling rate used by nearly all telephony systems, which use the g. Ee247 lecture 12 university of california, berkeley. The transition between continuous values of the image function and its digital equivalent is. Pdf on sep 16, 2019, zahraa chaffat oleiwi and others published digital image processing. Whether averaged or not, the actual sample value obtained will rarely be the exact value of the underlying analog signal at some time. Quantization makes the range of a signal discrete, so that the quantized signal takes on only a discrete, usually finite, set of values. Sampling techniques we can say that there are three types of sampling.
With the advent of electronics and computers, almost all the technological functions are digitized so they. Sampling and quantization often the domain and the range of an original signal xt are modeled as continuous. In matlab, you can generate samples from a sine wave of frequency f at a sampling rate r for s seconds in the following way. In digital signal processing and related fields, sampling and quantization are two methods, rather steps, used in the discretization of an analog signal in converting it to a digital signal. Raw files contain only the audio data, without even a header on the file. Freedman department of statistics university of california berkeley, ca 94720 the basic idea in sampling is extrapolation from the part to the wholefrom the sample to the population. That is, the time or spatial coordinate t is allowed to take on arbitrary real values perhaps over some interval and the value xt of the signal itself is allowed to take on arbitrary real values again perhaps within some interval. The quantization of time has nothing to do with the quantization of space, this seems like a better physical theory to start with. The more a recording is transferred from one analog format to another, the. Image sampling and quantisation biomedical engineering. What is the difference between sampling and quantization.
The second box takes the samples, which have a continuous domain, and turn them into samples from a finite domainfrom a discrete domain. Chapter 5 sampling and quantization often the domain and the range of an original signal xt are modeled as contin uous. The sampling rate or frequency f s is the number of samples per second hz. Page 21 adc differential nonlinearity example 0 7 6 0. Interpolation is the process of guessing signal values at arbitrary instants of time, which fall in general in between. The sampling rate determines the spatial resolution of the digitized image, while the quantization level determines the number of grey levels in the digitized image. Understanding and minimising adc conversion errors figure 8.
Recall that a pdf fx satisfies the following properties. Information rates in sampling and quantization ieee journals. Sampling and quantization university of illinois at urbana. Jul 04, 2015 mostly almost all of the energy is contained in the 5hz4 khz range, allowing a sampling rate of 8 khz. Within the next decade most of communication will become digital, with analog communication playing a minor role. The population is sometimes rather mysteriously called the universe. Ee3414 multimedia communication systems i experiment. The controller in an analog control system uses analog electronic, mechanical, electromechanical, or hydraulic devices. Sampling sampling period t quantization interval q binary encoding binary codebook yao wang, 2006 ee3414. So digitizing the amplitudes is known as quantization. Sampling and quantization digital image processing.
The results presented also illuminate the tradeoff between sampling rate and number of quantization levels in a channel of fixed capacity. Lecture 11 data converters sampling, aliasing, reconstruction. Quantization digital signals sampling and quantization figure 4. Ee3414 multimedia communication systems i experiment one sampling and quantization yao wang and xiaofeng xu 1. Sampling, quantization, and pulse code modulation pcm introduction. Quantization is the process of mapping a continuous or discrete scalar or vector. Assign points to a quantization level and reconstruct image. The fact that beer is sold in bottles has noting to do with being.
Probability density function pdf uniformly distributed from. Unlike sampling where we saw that under suitable conditions exact reconstruction is possible, quantization is generally irreversible and results in loss of information. To exemplify this operation, lets simulate an unipolar adc analog to digital converter having the technical specifications. The uniform sampling theorem states that a bandlimited signal having no spectral components above. Data sampling and quantization data sampling and quantization. Difference between sampling and quantization compare the. Consider an electrical signal whose horizontal axis represents time in seconds. Log in to save your progress and obtain a certificate in alisons free data science working with data online course. Image sampling and quantisation sampling of a continuous 1d function 2 all the frequency domain information of a bandlimited function is contained in the interval if the whittakershannon sampling theorem or nyquist sampling theorem 4. On the x axis of the signal, are the coordinate values, and on the y axis, we have amplitudes.
Sep 03, 2012 1 comparators, gmc filters, sc filters in cmos technology ppt 2 i lab session ppt ppt ii lab session manual pdf day 3 prof nagendra krishnapura basics of sampling and quantization vedio. Craig 11 an analog signal that varies quickly must be sampled more frequently than an analog signal that varies slowly. When you are quantizing an image, you are actually dividing a signal into quanta partitions. Quantization quantization is done by replacing each value of an analog signal xt by the value of the nearest quantization level. As nouns the difference between sampling and quantization is that sampling is the process or technique of obtaining a representative sample while quantization is uncountablesignal processing the process of approximating a continuous signal by a set of discrete symbols or integer values. Rayburn digital audio combines sampling quantization quantization turning a level into a number imagine you have two water glasses. If the desired sampling rate is lower than the sampling rate of the available data, in this case, we may use a process called downsampling or decimation to reduce the sampling rate of the signal. Color quantization methods can be broadly classified in two categories according to their initial palette selection scheme. Effective color quantization using adaptive sampling. Pdf sampling is the first step in the process of converting a continuous analog signal to a. Mostly almost all of the energy is contained in the 5hz4 khz range, allowing a sampling rate of 8 khz. A study on sampling and quantization techniques of image.
The faster the sampling rate and the larger the sample size, the more accurately sound can be digitized. The analog signal, denotedxt, is continuous in both time and amplitude. Sampling allows the use of modern digital electronics to process. As nouns the difference between sampling and quantization is that sampling is the process or technique of obtaining a representative sample while quantization is uncountablesignal processing the process of approximating a continuous signal by a set of discrete symbols or. Sampling digital signals sampling and quantization somehow guess, what value the signal could probably take on in between our samples. The sampling period t s is the spacing between two adjacent samples, i.
Ee247 lecture 11 university of california, berkeley. Although a significant portion of communication today is in analog form, it is being replaced rapidly by digital communication. Introduction the purpose of this lab is for you to understand the principles of sampling a continuous time signal, increasing or decreasing the sampling rate of a. Log in to save your progress and obtain a certificate in alisons free data. Within the next decade most of communication will become digital, with. Sampling and reconstruction process sampling theorem. Raw files contain only the audio data, without even a.
834 1179 1405 215 186 561 630 551 786 619 1236 248 850 1064 1215 415 1115 1172 39 738 1265 42 1143 465 1231 527 637 1449 93 1440 815 1379 658 618 298 622