This document discusses digitization and sampling of multimedia signals. It explains that digitization involves sampling a continuous analogue signal at discrete intervals and quantizing the signal values to a fixed set of levels. This reduces the continuous signal to a sequence of discrete samples. Some information is lost in this process. The document discusses how to reconstruct the original analogue signal from the digital samples and the problems that can occur with undersampling, such as missing details between samples. It introduces the concept of the Nyquist rate for accurate reconstruction.
The document summarizes a multi-clue approach for detecting photo-based face spoofing attacks in face recognition systems. It fuses analysis of both static visual characteristics and video clues, such as motion and eye blinking. For static analysis, it extracts several visual representations from frames to compute scores. Video analysis examines motion and blinks. The scores are fused using different combination methods depending on the level of detected motion. Experimental results on a standard spoofing database show the fused approach is more effective and robust than static analysis alone, especially for higher quality spoofing attacks.
This document discusses network computing and client/server systems. It covers the following key points:
- Network computing involves connecting stand-alone computers via a switch, LAN, or internet and dividing an application into parts that can be processed on different nodes.
- Client/server systems use sockets to establish connections between clients and servers over a TCP port. Once connected, clients and servers can send and receive data via input/output streams.
- Remote procedure calls allow procedures located on one computer to be called from another computer over a network, with parameters and results passed between the computers.
The document summarizes a multi-clue approach for detecting photo-based face spoofing attacks in face recognition systems. It fuses analysis of both static visual characteristics and video clues, such as motion and eye blinking. For static analysis, it extracts several visual representations from frames to compute scores. Video analysis examines motion and blinks. The scores are fused using different combination methods depending on the level of detected motion. Experimental results on a standard spoofing database show the fused approach is more effective and robust than static analysis alone, especially for higher quality spoofing attacks.
This document discusses network computing and client/server systems. It covers the following key points:
- Network computing involves connecting stand-alone computers via a switch, LAN, or internet and dividing an application into parts that can be processed on different nodes.
- Client/server systems use sockets to establish connections between clients and servers over a TCP port. Once connected, clients and servers can send and receive data via input/output streams.
- Remote procedure calls allow procedures located on one computer to be called from another computer over a network, with parameters and results passed between the computers.
The document discusses the process of digitization. It explains that digitization involves sampling an analog signal at discrete time intervals and quantizing the sampled values to a fixed set of levels. This converts a continuously varying analog signal into a digital signal represented by discrete numbers. Sampling reduces the continuous signal to a sequence of equally spaced values, while quantization restricts the values to allowed levels represented in a fixed number of bits. Together, sampling and quantization allow analog signals from physical phenomena to be represented digitally.
This document provides an overview of key concepts in multimedia systems including digital video formats, properties of video such as frame rate and aspect ratio, video compression techniques, and video production equipment and processes. It covers analog vs digital video, interlacing vs progressive scanning, common video file formats like AVI, MOV, and MPG, and how to transfer video from a camcorder to a computer.
1. The document discusses raster graphics and vector graphics. Raster graphics represent images as a collection of pixels arranged in a grid, while vector graphics represent images using geometric primitives like points, lines, and shapes.
2. It explains raster graphics in more detail, noting that they store images as a grid of pixels at specific locations, with each pixel represented by a color value. Image quality can be affected by resolution (pixel count) and color depth (number of possible colors).
3. The document also covers color depth and color palettes, which allow images to use a reduced set of colors while still displaying the full range of colors. Color tables map each pixel's color value to a color from the palette.
This document discusses the history and evolution of multimedia and digital media technologies. It provides the following key points:
1. Multimedia is defined as a combination of different content forms, including text, audio, images, animations, video and interactive content. It is usually recorded, accessed and played through electronic devices.
2. Early multimedia technologies included printed materials, film, and audio recordings. The development of personal computers in the 1980s allowed for more interactive multimedia experiences.
3. The emergence of CD-ROMs and the Internet in the 1990s significantly expanded digital multimedia capabilities. People could now access vast amounts of multimedia content online through their computers.
4. Modern multimedia devices like smartphones and
Multimedia systems can combine various media types like text, images, audio, video, animation and interactivity. They allow augmentation of the real world through technologies like augmented reality. Such systems were demonstrated at electronics trade shows like E3 in 2009 and 2010, with Microsoft showcasing projects like Natal and Kinect which interpreted human gestures for game control.
This document discusses digitization and sampling of multimedia signals. It explains that digitization involves sampling a continuous analogue signal at discrete intervals and quantizing the signal values to a fixed set of levels. This reduces the continuous signal to a sequence of discrete samples. Some information is lost during this process. The document discusses how to reconstruct the original analogue signal from the digital samples and the problems that can occur from undersampling, such as distortions and artefacts. It notes that the sampling rate needs to be high enough to avoid losing important signal details between samples.
Vacation Bible School had over 139 children participate throughout the week, with 12 children deciding to accept Jesus. Activities included singing, lessons from the Bible, games, crafts and snacks. Many volunteers helped make VBS a success, from group leaders to those helping with registration, sound, photos and clean up. It was a fun week of learning about God's 10 Commandments.
The document discusses various number systems including decimal, binary, and signed binary numbers. It provides the following key points:
1) Decimal numbers use ten digits from 0-9 while binary only uses two digits, 0 and 1. Binary numbers represent values through place values determined by powers of two.
2) Conversions can be done between decimal and binary numbers through either summing the place value weights or repeated division/multiplication by two.
3) Binary arithmetic follows simple rules to add, subtract, multiply and divide numbers in binary representation.
4) Signed binary numbers use a sign bit to indicate positive or negative values, with the most common 2's complement form representing negative numbers as the 2's
This document discusses basic digital logic components and integrated circuits. It describes the three basic logic operations - NOT, AND, and OR. It then outlines several basic logic functions including comparison, arithmetic, code conversion, encoding/decoding, data selection, storage, and counting. Finally, it discusses different types of integrated circuits from small to very large scale, and introduces programmable logic devices like FPGAs and CPLDs.
Multimedia systems allow for the delivery of various media types such as audio, video, graphics, and text across computer networks and the internet. Content can be delivered through both offline and online methods using various networking technologies and protocols. Common online delivery methods include unicast, which sends content to individual clients, and multicast, which sends content simultaneously to multiple clients.
Digital audio technologies allow for the reproduction and manipulation of sound in digital form. Sound is converted from analog to digital via sampling, where the amplitude of sound waves is measured at regular intervals. This results in digital audio files that can be edited, stored and transmitted more easily than analog audio. Popular digital audio file formats include WAV, MP3, MIDI and more. Devices like the iPod and services like iTunes revolutionized portable music and digital music distribution. Technologies like text-to-speech and DAISY have also improved audio accessibility.
This document discusses message passing architectures. The key points are:
1) Message passing architectures allow processors to communicate data without a global memory by sending messages. Each processor has local memory and communicates via messages.
2) Important factors in message passing networks are link bandwidth and network latency.
3) Processes running on different processors use external channels to exchange messages, while processes on the same processor use internal channels. This avoids the need for synchronization.
Multimedia is a combination of different media types that can be used for multiple content forms. It includes a combination of text, audio, still images, animation, video, and interactive content. Multimedia is usually recorded and displayed or accessed through information processing devices like computers and electronic devices, but can also be part of a live performance. It is distinguished from mixed media by including audio. The term "rich media" is a synonym for interactive multimedia.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
The document discusses the process of digitization. It explains that digitization involves sampling an analog signal at discrete time intervals and quantizing the sampled values to a fixed set of levels. This converts a continuously varying analog signal into a digital signal represented by discrete numbers. Sampling reduces the continuous signal to a sequence of equally spaced values, while quantization restricts the values to allowed levels represented in a fixed number of bits. Together, sampling and quantization allow analog signals from physical phenomena to be represented digitally.
This document provides an overview of key concepts in multimedia systems including digital video formats, properties of video such as frame rate and aspect ratio, video compression techniques, and video production equipment and processes. It covers analog vs digital video, interlacing vs progressive scanning, common video file formats like AVI, MOV, and MPG, and how to transfer video from a camcorder to a computer.
1. The document discusses raster graphics and vector graphics. Raster graphics represent images as a collection of pixels arranged in a grid, while vector graphics represent images using geometric primitives like points, lines, and shapes.
2. It explains raster graphics in more detail, noting that they store images as a grid of pixels at specific locations, with each pixel represented by a color value. Image quality can be affected by resolution (pixel count) and color depth (number of possible colors).
3. The document also covers color depth and color palettes, which allow images to use a reduced set of colors while still displaying the full range of colors. Color tables map each pixel's color value to a color from the palette.
This document discusses the history and evolution of multimedia and digital media technologies. It provides the following key points:
1. Multimedia is defined as a combination of different content forms, including text, audio, images, animations, video and interactive content. It is usually recorded, accessed and played through electronic devices.
2. Early multimedia technologies included printed materials, film, and audio recordings. The development of personal computers in the 1980s allowed for more interactive multimedia experiences.
3. The emergence of CD-ROMs and the Internet in the 1990s significantly expanded digital multimedia capabilities. People could now access vast amounts of multimedia content online through their computers.
4. Modern multimedia devices like smartphones and
Multimedia systems can combine various media types like text, images, audio, video, animation and interactivity. They allow augmentation of the real world through technologies like augmented reality. Such systems were demonstrated at electronics trade shows like E3 in 2009 and 2010, with Microsoft showcasing projects like Natal and Kinect which interpreted human gestures for game control.
This document discusses digitization and sampling of multimedia signals. It explains that digitization involves sampling a continuous analogue signal at discrete intervals and quantizing the signal values to a fixed set of levels. This reduces the continuous signal to a sequence of discrete samples. Some information is lost during this process. The document discusses how to reconstruct the original analogue signal from the digital samples and the problems that can occur from undersampling, such as distortions and artefacts. It notes that the sampling rate needs to be high enough to avoid losing important signal details between samples.
Vacation Bible School had over 139 children participate throughout the week, with 12 children deciding to accept Jesus. Activities included singing, lessons from the Bible, games, crafts and snacks. Many volunteers helped make VBS a success, from group leaders to those helping with registration, sound, photos and clean up. It was a fun week of learning about God's 10 Commandments.
The document discusses various number systems including decimal, binary, and signed binary numbers. It provides the following key points:
1) Decimal numbers use ten digits from 0-9 while binary only uses two digits, 0 and 1. Binary numbers represent values through place values determined by powers of two.
2) Conversions can be done between decimal and binary numbers through either summing the place value weights or repeated division/multiplication by two.
3) Binary arithmetic follows simple rules to add, subtract, multiply and divide numbers in binary representation.
4) Signed binary numbers use a sign bit to indicate positive or negative values, with the most common 2's complement form representing negative numbers as the 2's
This document discusses basic digital logic components and integrated circuits. It describes the three basic logic operations - NOT, AND, and OR. It then outlines several basic logic functions including comparison, arithmetic, code conversion, encoding/decoding, data selection, storage, and counting. Finally, it discusses different types of integrated circuits from small to very large scale, and introduces programmable logic devices like FPGAs and CPLDs.
Multimedia systems allow for the delivery of various media types such as audio, video, graphics, and text across computer networks and the internet. Content can be delivered through both offline and online methods using various networking technologies and protocols. Common online delivery methods include unicast, which sends content to individual clients, and multicast, which sends content simultaneously to multiple clients.
Digital audio technologies allow for the reproduction and manipulation of sound in digital form. Sound is converted from analog to digital via sampling, where the amplitude of sound waves is measured at regular intervals. This results in digital audio files that can be edited, stored and transmitted more easily than analog audio. Popular digital audio file formats include WAV, MP3, MIDI and more. Devices like the iPod and services like iTunes revolutionized portable music and digital music distribution. Technologies like text-to-speech and DAISY have also improved audio accessibility.
This document discusses message passing architectures. The key points are:
1) Message passing architectures allow processors to communicate data without a global memory by sending messages. Each processor has local memory and communicates via messages.
2) Important factors in message passing networks are link bandwidth and network latency.
3) Processes running on different processors use external channels to exchange messages, while processes on the same processor use internal channels. This avoids the need for synchronization.
Multimedia is a combination of different media types that can be used for multiple content forms. It includes a combination of text, audio, still images, animation, video, and interactive content. Multimedia is usually recorded and displayed or accessed through information processing devices like computers and electronic devices, but can also be part of a live performance. It is distinguished from mixed media by including audio. The term "rich media" is a synonym for interactive multimedia.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
How to Manage Your Lost Opportunities in Odoo 17 CRMCeline George
Odoo 17 CRM allows us to track why we lose sales opportunities with "Lost Reasons." This helps analyze our sales process and identify areas for improvement. Here's how to configure lost reasons in Odoo 17 CRM
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
আমাদের সবার জন্য খুব খুব গুরুত্বপূর্ণ একটি বই ..বিসিএস, ব্যাংক, ইউনিভার্সিটি ভর্তি ও যে কোন প্রতিযোগিতা মূলক পরীক্ষার জন্য এর খুব ইম্পরট্যান্ট একটি বিষয় ...তাছাড়া বাংলাদেশের সাম্প্রতিক যে কোন ডাটা বা তথ্য এই বইতে পাবেন ...
তাই একজন নাগরিক হিসাবে এই তথ্য গুলো আপনার জানা প্রয়োজন ...।
বিসিএস ও ব্যাংক এর লিখিত পরীক্ষা ...+এছাড়া মাধ্যমিক ও উচ্চমাধ্যমিকের স্টুডেন্টদের জন্য অনেক কাজে আসবে ...
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
21. 22 F U N DA M E N TA L S not usually distinguishing between time-varying and space-varying bit
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When we have a continuously varying sign measu
Figure 2.2. An analogue signal
In multimedia, we encounter values of several kinds that change continuously, either the value we measure,
in Figure 2.2, both because we re
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they originate in physical phenomena or because they exist in some can measure it, can vary infinitesimally.
we analogue representation.
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convert it to a digital signal,
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have
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colour of the image formed inside a camera by its lens varies continuously across the digitization – the process o
image plane.
of bits. That is, one li
As you see, we may be measuring different quantities, and they mayanalogue to either over timeconsists of two
be varying digital form –
or over space (or perhaps, as in the case of moving pictures, both). For this general discussion, we discrete interva
measure the signal’s value at These
will follow tradition, and refer to the
Figure value we are measuring, whatever it may be, as a “signal”,
2.2. An analogue signal
:6JGA/:16 Analogue to Digital Converter (ADC)
we restrict the value to a fixed set of levels.
called
not usually distinguishing between time-varying and space-varying signals. carried out in either order; Figure
can be we w
first sampled and then quantized. In where the s
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continuous signal reduced to sampl
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quantization step, at which rate.
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convert it to a digital signal, we would have to restrict both of these to
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of bits. That is, digitization – the processcalled analogue atosignal from
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those
analogue to digital form – consists of two steps:not examine. We will only consider a
we will sampling, when we over
measure the signal’s value at discrete intervals, and quantization, whensuccessive inevit
where the interval between samp
Figure 2.2. An analogue signal Figure 2.3. Sampling and
we restrict the value to a fixed set of levels. Samplingaand quantization time or space
quantization
samples in fixed amount of ence
can be carried out in either order; Figure 2.3 shows we will generally assume that
rate. Similarly, a signal being
$+LL1M first sampled and then quantized. In theissampling step, you see the levels – are
sampling quantization
quantizedapisake@gmail.com.................
Ex Libris – the quantization
analogue continuous signal reduced to a sequence of equally spaced values; in the
quantization step, some of these values are chopped off so that every that digital
One of the great advantages
one lies on one of the lines defining the allowed levels. stems from the fact that on
analogue ones
those at the quantization levels – are valid
22. 22 F U N DA M E N TA L S not usually distinguishing between time-varying and space-varying bit
of sig
analog
When we have a continuously varying sign measu
Figure 2.2. An analogue signal
In multimedia, we encounter values of several kinds that change continuously, either the value we measure,
in Figure 2.2, both because
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they originate in physical phenomena or because they exist in some can measure it, can vary infinitesimally.
we analogue representation.
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For example, the amplitude (volume) of a sound wave varies continuously over time, as does thewe would first s
convert it to a digital signal,
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amplitude of an electrical signal produced by a microphone in response to a sound wave. The contin
a set of discrete values that could be represen
quant
colour of the image formed inside a camera by its lens varies continuously across the digitization – the process o
image plane.
of bits. That is, one li
As you see, we may be measuring different quantities, and they mayanalogue to either over timeconsists of two
be varying digital form –
or over space (or perhaps, as in the case of moving pictures, both). For this general discussion, we discrete interva
measure the signal’s value at These
will follow tradition, and refer to the
Figure value we are measuring, whatever it may be, as a “signal”,
2.2. An analogue signal
:6JGA/:16 Analogue to Digital Converter (ADC)
we restrict the value to a fixed set of levels.
called
not usually distinguishing between time-varying and space-varying signals. carried out in either order; Figure
can be we w
first sampled and then quantized. In where the s
When we have a continuously varying signal, such as the one shown a sequence of e
continuous signal reduced to sampl
in Figure 2.2, both the value we measure, and the intervalssome of these values areS
quantization step, at which rate.
we can measure it, can vary infinitesimally. Inlies on one of the lines defining the qua
one contrast, if we were to
is
allo
convert it to a digital signal, we would have to restrict both of these to
One
a set of discrete values that could be represented in some fixed normally carried out b
These processes are number
analog
of bits. That is, digitization – the processcalled analogue atosignal from
of converting digital converters (ADCs
those
analogue to digital form – consists of two steps:not examine. We will only consider a
we will sampling, when we over
measure the signal’s value at discrete intervals, and quantization, whensuccessive inevit
where the interval between samp
Figure 2.2. An analogue signal Figure 2.3. Sampling and
we restrict the value to a fixed set of levels. Samplingaand quantization time or space
quantization
samples in fixed amount of ence
can be carried out in either order; Figure 2.3 shows we will generally assume that
rate. Similarly, a signal being
$+LL1M first sampled and then quantized. In theissampling step, you see the levels – are
sampling quantization
quantizedapisake@gmail.com.................
Ex Libris – the quantization
analogue continuous signal reduced to a sequence of equally spaced values; in the
quantization step, some of these values are chopped off so that every that digital
One of the great advantages
one lies on one of the lines defining the allowed levels. stems from the fact that on
analogue ones
those at the quantization levels – are valid
24. Digitization
24 F U N DA M E N TA L S
:16 undersampl
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the same level. The effects of such undersampling " way ,I#
:7;/(' :I" perceived depend on
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are always undesirable.
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any rate at which we can be sure that the samples are close enough
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a signal. Later, this will also help us to understand some related aspects
Nyquist rate
of sound and image processing.
You are probably familiar with the idea that a musical note played on
an instrument consists of waveforms of several different frequencies
34. CHAPTER
2 D I G I TA L DATA
Figure 2.12. Posterization
between areas of those colours would be elided. The effect on black and white images can be
seen clearly in Figure 2.11, which shows a gradient swatch using 256, 128, 64, 32, 16, 8, 4, and
2 different grey levels. The original gradient varies linearly from pure white to pure black, and
as we reduce the number of different greys, you can see how values band together as they are
36. 2
Compression
CHAPTER DIGITAL DATA 31
You will learn, as we examine the individual media types in detail, that a characteristic property
Compression of media data is that it occupies a lot of storage. This means, in turn, that it needs a lot of band-
width when it is transferred over networks. Storage and bandwidth are limited resources, so the
with directly, so storage schemes which make less than optimal use of
the available bits are usedhigh demands of instead. data can pose a problem. The common response to this problem is to
most of the time media
original data
apply some form of compression, which means any operation that can be performed on data to
Lossless and lossy compression arethe amount separate techniques. Mostrepresent it. If data has been compressed, an inverse
reduce not entirely of storage required to
lossy algorithms make use of some lossless technique as part required to restore it to a form in which it can be displayed or
decompression operation will be of the total
compression process. Generally,Software that performs compression and decompression is often called a codec (short for
used. once insignificant information has been compress
discarded, the resulting data is more amenable to lossless compression. context of video and audio.
compressor/decompressor), especially in the
This is particularly true in the case of image compression, as we will
explain in Chapter 4. Compression algorithms can be divided into two classes: lossless and
lossy. A lossless algorithm hascompressed datathat it is always possible to
the property
Ideally, lossy compression will data be applied atdecompresspossible
original only the latest data that has been compressed and retrieve an exact copy
stage in the preparation of the media for delivery. Any processing that as indicated in Figure 2.13. Any compression algo-
of the original data, decompress
is required should be done on uncompressed or losslesslythat is not lossless is lossy, which means that some data has been
rithm compressed
data whenever possible. There are two reasons for this. When data is
compress discarded in the compression process and cannot be restored, so that the
lossily compressed the lost information can never be retrieved, which
decompressed data is only an approximation to the original, as shown
means that if data is repeatedly compressed and decompressed in this
in Figure 2.14. The discarded data will represent information that is
way its quality will gradually deteriorate. Additionally, some processing
decompress
not significant, and lossy algorithms which are in common use do a
operations can exaggerate the loss of quality caused by some types of
remarkable uncom- preserving the qualitydata images, video and sound,
compression. For both these reasons, it is best to work with
job at decompressed of
compressed data
pressed data, and only compress it for final delivery. even though a considerable amount of data has been discarded. Lossless
Figure 2.13. Lossless compression algorithms are generally less effective than lossy ones, so for most multi-
media applications Figure 2.14. Lossy compression
This ideal cannot always be achieved.Video data is usually compressed in some lossy compression will be used. However, for
the camera, and although text the loss of even a produce uncompressed
digital still cameras that single bit of information would be significant, so there is no such thing as
lossy text compression.
images are increasingly common, many cheaper cameras will compress photographs fairly severely
when the pictures are being taken. It may be necessary for a photographer to allow the camera to
compress images, in order to fit thembe apparent that any sort of data these circumstances, data without loss. If no informa-
It may not onto the available storage. Under can be compressed at all