This document discusses digital video and audio fundamentals. It covers types of video signals like component, composite, and S-video. It then discusses analog video standards like NTSC, PAL, and SECAM, including details on frame rates, resolution, and color models. It also covers digital video concepts such as chroma subsampling and standards like CCIR 601. Finally, it briefly discusses digital audio topics like MIDI and quantization.
This slide gives you the basic understanding of digital image compression.
Please Note: This is a class teaching PPT, more and detail topics were covered in the classroom.
The document discusses various aspects of video systems and design, including how video works, different broadcast standards, analog and digital video formats, video recording tape formats, shooting and editing video, and optimizing video files. It provides details on video compression standards like MPEG and considerations for integrating video into multimedia projects. Overall, the document serves as a guide for understanding video technology and best practices for using video effectively in multimedia design.
The document discusses audio compression techniques. It begins with an introduction to pulse code modulation (PCM) and then describes μ-law and A-law compression standards which compress audio using companding algorithms. It also covers differential PCM and adaptive differential PCM (ADPCM) techniques. The document then discusses the MPEG audio compression standard, including its encoder architecture, three layer standards (Layers I, II, III), and applications. It concludes with a comparison of various MPEG audio compression standards and references.
This document discusses digital audio and summarizes key points:
1. Digital audio involves converting sound waves to numerical data that can be easily stored, manipulated and reproduced. It allows for two types of sounds - analog and digital.
2. Characteristics of digital audio include sampling rate, amplitude, channels. Common sampling rates are 11.025KHz, 22.5KHz and 44.1KHz. File size is calculated based on these characteristics.
3. Popular audio file formats include WAV, AIFF, MP3, AAC which allow for compression. MIDI stores musical data separately from audio and allows for editing of notes.
This document discusses digital audio technology. It covers characteristics of sound and how it is digitized. Digital audio systems allow editing of audio through techniques like trimming and volume adjustments. Common audio file formats are also described like WAV, AIFF, and MIDI. The document explains how audio is used to enhance multimedia applications and manage software functions.
introduction to audio formats - Multimedia StudentsSEO SKills
This document discusses audio file formats. It begins by explaining what sound is and how it is digitized through sampling and quantization. It then covers both uncompressed formats like PCM, WAV, and AIFF as well as compressed formats. Lossy formats discussed include MP3, AAC, OGG, and WMA, while lossless formats include FLAC, ALAC, and WMA Lossless. The document recommends using uncompressed formats for raw audio work, lossless compression like FLAC for high-quality music listening, and lossy compression if storage space needs to be conserved or quality is less important.
Sound is created by vibrations that travel through a medium like air as sound waves. It has two main characteristics - frequency determines pitch, and amplitude determines loudness. Digital audio involves sampling an analog sound wave into discrete numeric samples at a certain rate. MIDI data provides instructions for synthesizing music rather than storing actual sound samples. When adding audio to multimedia projects, the file format, playback capabilities, and intended function of the sound must be considered.
This slide gives you the basic understanding of digital image compression.
Please Note: This is a class teaching PPT, more and detail topics were covered in the classroom.
The document discusses various aspects of video systems and design, including how video works, different broadcast standards, analog and digital video formats, video recording tape formats, shooting and editing video, and optimizing video files. It provides details on video compression standards like MPEG and considerations for integrating video into multimedia projects. Overall, the document serves as a guide for understanding video technology and best practices for using video effectively in multimedia design.
The document discusses audio compression techniques. It begins with an introduction to pulse code modulation (PCM) and then describes μ-law and A-law compression standards which compress audio using companding algorithms. It also covers differential PCM and adaptive differential PCM (ADPCM) techniques. The document then discusses the MPEG audio compression standard, including its encoder architecture, three layer standards (Layers I, II, III), and applications. It concludes with a comparison of various MPEG audio compression standards and references.
This document discusses digital audio and summarizes key points:
1. Digital audio involves converting sound waves to numerical data that can be easily stored, manipulated and reproduced. It allows for two types of sounds - analog and digital.
2. Characteristics of digital audio include sampling rate, amplitude, channels. Common sampling rates are 11.025KHz, 22.5KHz and 44.1KHz. File size is calculated based on these characteristics.
3. Popular audio file formats include WAV, AIFF, MP3, AAC which allow for compression. MIDI stores musical data separately from audio and allows for editing of notes.
This document discusses digital audio technology. It covers characteristics of sound and how it is digitized. Digital audio systems allow editing of audio through techniques like trimming and volume adjustments. Common audio file formats are also described like WAV, AIFF, and MIDI. The document explains how audio is used to enhance multimedia applications and manage software functions.
introduction to audio formats - Multimedia StudentsSEO SKills
This document discusses audio file formats. It begins by explaining what sound is and how it is digitized through sampling and quantization. It then covers both uncompressed formats like PCM, WAV, and AIFF as well as compressed formats. Lossy formats discussed include MP3, AAC, OGG, and WMA, while lossless formats include FLAC, ALAC, and WMA Lossless. The document recommends using uncompressed formats for raw audio work, lossless compression like FLAC for high-quality music listening, and lossy compression if storage space needs to be conserved or quality is less important.
Sound is created by vibrations that travel through a medium like air as sound waves. It has two main characteristics - frequency determines pitch, and amplitude determines loudness. Digital audio involves sampling an analog sound wave into discrete numeric samples at a certain rate. MIDI data provides instructions for synthesizing music rather than storing actual sound samples. When adding audio to multimedia projects, the file format, playback capabilities, and intended function of the sound must be considered.
H.261 is a video coding standard published in 1990 by ITU-T for videoconferencing over ISDN networks. It uses techniques like DCT, motion compensation, and entropy coding to achieve compression ratios over 100:1 for video calling. H.261 remains widely used in applications like Windows NetMeeting and video conferencing standards H.320, H.323, and H.324.
This presentation is about JPEG compression algorithm. It briefly describes all the underlying steps in JPEG compression like picture preparation, DCT, Quantization, Rendering and Encoding.
This document summarizes common image file formats, including their extensions, color capabilities, compression types, and common uses. JPEG files use lossy compression and support up to 24-bit color for photos shared on the web. GIF files use lossless compression and are limited to 8-bit color, making them suited for simple web graphics like buttons and icons. PNG files can support up to 24-bit color and use lossless compression, intended as a replacement for GIF files. TIFF files support 24-bit color and various compression types, used commonly for professional photos.
The document discusses the relationship between pixels in an image, including pixel neighborhoods and connectivity. It defines different types of pixel neighborhoods - the 4 nearest neighbors, 8 nearest neighbors including diagonals, and boundary pixels that have fewer than 8 neighbors. Connectivity refers to whether two pixels are adjacent or connected based on their intensity values and neighborhood relationships. Specifically, it describes 4-connectivity, 8-connectivity, and m-connectivity. Regions in an image are sets of connected pixels, while boundaries separate adjacent regions.
This document provides an overview of digital image fundamentals including:
- The electromagnetic spectrum and how light is sensed and sampled by sensor arrays to create digital images.
- Common sensor technologies like CCD and CMOS sensors and how they work.
- How digital images are represented through spatial and intensity discretization via sampling and quantization.
- Factors that affect image quality like spatial and intensity resolution.
- Concepts like aliasing, moire patterns, and their relationship to sampling rates.
- Basic image processing techniques like zooming, shrinking, and relationships between pixels.
This presentation is focused on basic understanding of video signal generation and its electronic interpretation. Contents are taken from bible of television!
This presentation is dedicated to R R Gulati.
This document discusses animation techniques and principles. It begins by outlining the structure of animation and principles like persistence of vision. It then discusses different types of animation including 2D, 2.5D, and 3D animation. The document details the process of cel animation including keyframes and tweening. It also discusses computer animation software, file formats for animation, and considerations for using animation effectively.
The document discusses various file formats for different types of digital media. It describes audio, video, and image file formats. For audio formats, it discusses MP3, WAV, WMA, and Ogg formats. For video formats, it covers AVI, WMV, MOV, and MP4. For images, it summarizes JPG, TIF, GIF, and PNG formats. It provides details on each format such as how they are compressed, supported file extensions and applications, and strengths and limitations.
The document discusses different types of video compression standards including MPEG, H.261, H.263, and JPEG. It explains key concepts in video compression like frame rate, color resolution, spatial resolution, and image quality. MPEG standards like MPEG-1, MPEG-2, MPEG-4, and MPEG-7 are defined for compressing video and audio at different bit rates. Techniques like spatial and temporal redundancy reduction are used to compress video frames and consecutive frames. Compression reduces file sizes but can cause data loss during transmission.
Lecture 1 for Digital Image Processing (2nd Edition)Moe Moe Myint
-What is Digital Image Processing?
-The Origins of Digital Image Processing
-Examples of Fields that Use Digital Image Processing
-Fundamentals Steps in Digital Image Processing
-Components of an Image Processing System
This document provides an overview of audio compression technologies. It discusses what audio is, why compression is needed, and the main types of audio compression: lossy and lossless. It describes some standard codecs for each type including MP3, AAC, FLAC. It explains the MPEG audio encoding and decoding process, and notes that AAC is the successor to MP3. In summary, the document covers audio fundamentals and provides details on common audio compression standards and techniques.
The document discusses sound and audio for multimedia projects. It covers digital audio, MIDI audio, audio file formats, and how to incorporate sound into multimedia projects. Some key points include: MIDI represents musical instructions while digital audio is recorded sound; digital audio is device independent but MIDI depends on the playback hardware; common audio editing tasks involve trimming, splicing, and adjusting volume; and file size must be balanced with audio quality for digital files.
Audio compression can be either lossless, which reduces file size while retaining all audio information, or lossy, which greatly reduces file size but decreases sound quality by losing some audio information. Common lossless formats are AIFF, WAV, and FLAC, while common lossy formats are MP3, AAC, and Vorbis. The quality and size of compressed audio files depends on factors like sample rate, bit depth, bit rate, and number of channels. Higher values for these factors generally mean higher quality audio but larger file sizes.
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
This document discusses color image processing and provides details on color fundamentals, color models, and pseudocolor image processing techniques. It introduces color image processing, full-color versus pseudocolor processing, and several color models including RGB, CMY, and HSI. Pseudocolor processing techniques of intensity slicing and gray level to color transformation are explained, where grayscale values in an image are assigned colors based on intensity ranges or grayscale levels.
Digital video has replaced analog video as the preferred method for making and delivering video content in multimedia. Video files can be extremely large, so compression techniques like MPEG and JPEG are used to reduce file sizes. There are two types of compression: lossless, which preserves quality, and lossy, which eliminates some data to provide greater compression ratios at the cost of quality. Digital video editing software allows for adding effects, transitions, titles and synchronizing video and audio.
Sound is created by vibrations that travel as waves through air or another medium. These sound waves can be captured and converted into digital audio files through a process called digitization. The quality of a digital audio file depends on factors like the sampling rate, which is the number of times per second the sound wave is measured, and the sample size or bit depth, which determines how finely variations in the amplitude of the sound wave are recorded. Higher sampling rates and more bits per sample result in better quality recordings but larger file sizes.
This document discusses fundamental concepts in digital video. It begins by explaining the differences between analog and digital video, and how digital video allows for direct access and repeated recording without quality degradation. It then examines various digital video standards including CCIR 601, CIF, and QCIF. It provides details on chroma subsampling ratios and how they reduce data requirements. The document also covers high-definition television standards and aims to increase the visual field rather than definition per unit area.
This document provides an overview of fundamental concepts in video and multimedia technology. It discusses the differences between analog and digital video, including how analog video uses continuous electric signals while digital video represents images as binary digits. It also covers topics like interlaced vs progressive scanning, component vs composite video signals, common video file formats, and standards for analog TV broadcasting like NTSC, PAL, and SECAM. Key video concepts like frame rate, color resolution, spatial resolution, and image quality that apply to digital video are also defined.
H.261 is a video coding standard published in 1990 by ITU-T for videoconferencing over ISDN networks. It uses techniques like DCT, motion compensation, and entropy coding to achieve compression ratios over 100:1 for video calling. H.261 remains widely used in applications like Windows NetMeeting and video conferencing standards H.320, H.323, and H.324.
This presentation is about JPEG compression algorithm. It briefly describes all the underlying steps in JPEG compression like picture preparation, DCT, Quantization, Rendering and Encoding.
This document summarizes common image file formats, including their extensions, color capabilities, compression types, and common uses. JPEG files use lossy compression and support up to 24-bit color for photos shared on the web. GIF files use lossless compression and are limited to 8-bit color, making them suited for simple web graphics like buttons and icons. PNG files can support up to 24-bit color and use lossless compression, intended as a replacement for GIF files. TIFF files support 24-bit color and various compression types, used commonly for professional photos.
The document discusses the relationship between pixels in an image, including pixel neighborhoods and connectivity. It defines different types of pixel neighborhoods - the 4 nearest neighbors, 8 nearest neighbors including diagonals, and boundary pixels that have fewer than 8 neighbors. Connectivity refers to whether two pixels are adjacent or connected based on their intensity values and neighborhood relationships. Specifically, it describes 4-connectivity, 8-connectivity, and m-connectivity. Regions in an image are sets of connected pixels, while boundaries separate adjacent regions.
This document provides an overview of digital image fundamentals including:
- The electromagnetic spectrum and how light is sensed and sampled by sensor arrays to create digital images.
- Common sensor technologies like CCD and CMOS sensors and how they work.
- How digital images are represented through spatial and intensity discretization via sampling and quantization.
- Factors that affect image quality like spatial and intensity resolution.
- Concepts like aliasing, moire patterns, and their relationship to sampling rates.
- Basic image processing techniques like zooming, shrinking, and relationships between pixels.
This presentation is focused on basic understanding of video signal generation and its electronic interpretation. Contents are taken from bible of television!
This presentation is dedicated to R R Gulati.
This document discusses animation techniques and principles. It begins by outlining the structure of animation and principles like persistence of vision. It then discusses different types of animation including 2D, 2.5D, and 3D animation. The document details the process of cel animation including keyframes and tweening. It also discusses computer animation software, file formats for animation, and considerations for using animation effectively.
The document discusses various file formats for different types of digital media. It describes audio, video, and image file formats. For audio formats, it discusses MP3, WAV, WMA, and Ogg formats. For video formats, it covers AVI, WMV, MOV, and MP4. For images, it summarizes JPG, TIF, GIF, and PNG formats. It provides details on each format such as how they are compressed, supported file extensions and applications, and strengths and limitations.
The document discusses different types of video compression standards including MPEG, H.261, H.263, and JPEG. It explains key concepts in video compression like frame rate, color resolution, spatial resolution, and image quality. MPEG standards like MPEG-1, MPEG-2, MPEG-4, and MPEG-7 are defined for compressing video and audio at different bit rates. Techniques like spatial and temporal redundancy reduction are used to compress video frames and consecutive frames. Compression reduces file sizes but can cause data loss during transmission.
Lecture 1 for Digital Image Processing (2nd Edition)Moe Moe Myint
-What is Digital Image Processing?
-The Origins of Digital Image Processing
-Examples of Fields that Use Digital Image Processing
-Fundamentals Steps in Digital Image Processing
-Components of an Image Processing System
This document provides an overview of audio compression technologies. It discusses what audio is, why compression is needed, and the main types of audio compression: lossy and lossless. It describes some standard codecs for each type including MP3, AAC, FLAC. It explains the MPEG audio encoding and decoding process, and notes that AAC is the successor to MP3. In summary, the document covers audio fundamentals and provides details on common audio compression standards and techniques.
The document discusses sound and audio for multimedia projects. It covers digital audio, MIDI audio, audio file formats, and how to incorporate sound into multimedia projects. Some key points include: MIDI represents musical instructions while digital audio is recorded sound; digital audio is device independent but MIDI depends on the playback hardware; common audio editing tasks involve trimming, splicing, and adjusting volume; and file size must be balanced with audio quality for digital files.
Audio compression can be either lossless, which reduces file size while retaining all audio information, or lossy, which greatly reduces file size but decreases sound quality by losing some audio information. Common lossless formats are AIFF, WAV, and FLAC, while common lossy formats are MP3, AAC, and Vorbis. The quality and size of compressed audio files depends on factors like sample rate, bit depth, bit rate, and number of channels. Higher values for these factors generally mean higher quality audio but larger file sizes.
This is the subject slides for the module MMS2401 - Multimedia System and Communication taught in Shepherd College of Media Technology, Affiliated with Purbanchal University.
This document discusses color image processing and provides details on color fundamentals, color models, and pseudocolor image processing techniques. It introduces color image processing, full-color versus pseudocolor processing, and several color models including RGB, CMY, and HSI. Pseudocolor processing techniques of intensity slicing and gray level to color transformation are explained, where grayscale values in an image are assigned colors based on intensity ranges or grayscale levels.
Digital video has replaced analog video as the preferred method for making and delivering video content in multimedia. Video files can be extremely large, so compression techniques like MPEG and JPEG are used to reduce file sizes. There are two types of compression: lossless, which preserves quality, and lossy, which eliminates some data to provide greater compression ratios at the cost of quality. Digital video editing software allows for adding effects, transitions, titles and synchronizing video and audio.
Sound is created by vibrations that travel as waves through air or another medium. These sound waves can be captured and converted into digital audio files through a process called digitization. The quality of a digital audio file depends on factors like the sampling rate, which is the number of times per second the sound wave is measured, and the sample size or bit depth, which determines how finely variations in the amplitude of the sound wave are recorded. Higher sampling rates and more bits per sample result in better quality recordings but larger file sizes.
This document discusses fundamental concepts in digital video. It begins by explaining the differences between analog and digital video, and how digital video allows for direct access and repeated recording without quality degradation. It then examines various digital video standards including CCIR 601, CIF, and QCIF. It provides details on chroma subsampling ratios and how they reduce data requirements. The document also covers high-definition television standards and aims to increase the visual field rather than definition per unit area.
This document provides an overview of fundamental concepts in video and multimedia technology. It discusses the differences between analog and digital video, including how analog video uses continuous electric signals while digital video represents images as binary digits. It also covers topics like interlaced vs progressive scanning, component vs composite video signals, common video file formats, and standards for analog TV broadcasting like NTSC, PAL, and SECAM. Key video concepts like frame rate, color resolution, spatial resolution, and image quality that apply to digital video are also defined.
An analog video camera converts light intensity to an electric signal that varies over time. There are different types of analog video signals including NTSC, PAL, and SECAM. Digital video represents images as pixels. Digital video compression uses chroma subsampling and different schemes like 4:4:4, 4:2:2, and 4:2:0. Popular digital video compression standards include MPEG-1, MPEG-2, H.261, and H.263 which use techniques like intra and inter frames, motion compensation, and temporal redundancy to reduce file sizes.
This document discusses fundamental concepts in analog and digital video, including:
- Analog video uses continuous electrical signals to represent images, while digital video uses discrete 1s and 0s. Analog video is susceptible to quality loss but digital video maintains perfect quality.
- There are different types of color video signals like composite, S-video, and component, with component providing the best quality but requiring more bandwidth.
- Common video broadcasting standards are NTSC, PAL, and SECAM, which specify resolutions and frame rates and differ in color encoding schemes.
This document provides an overview of fundamental concepts in video, including analog video, digital video, color video signals, and video broadcasting standards. It discusses the following key points in 3 sentences:
Analog video uses continuous electrical signals to represent images and sounds, but is prone to distortion and noise. Digital video represents images using binary digits, allowing for exact copies without quality degradation. Major video standards include NTSC, PAL, and SECAM which specify resolutions and frame rates for analog broadcast television.
Unit ii mm_chap5_fundamentals concepts in videoEellekwameowusu
This document discusses different types of video signals including component, composite, S-video, and digital video. It describes analog video standards like NTSC and PAL used in television broadcasts. NTSC uses interlaced scanning at 525 lines per frame and 29.97 frames per second. It transmits color information using the YIQ color model and quadrature amplitude modulation. PAL and SECAM are similar but use different color encoding schemes. Digital video offers advantages like random access and resistance to degradation from repeated recording. Chroma subsampling reduces color resolution to reduce file size.
This document discusses the digital representation of various media types including images, video, and audio. It covers topics such as how images are represented digitally through pixels, common image file formats, and color models. For video, it describes properties like frame rate and scanning format as well as analog video standards. It also discusses digital video formats and surround sound representation for audio. Common graphic representations and animations using 2D vectors are also summarized.
The document discusses key concepts in digital video, including:
1) Persistence of vision and scanning processes using a cathode ray tube to display video frames made up of scan lines.
2) Analog video signals can pick up noise while digital video uses sampling and compression.
3) Digital video formats like DV use color sampling and compression standards to efficiently capture and store video data, which can then be edited nonlinearly.
4) DV connects to computers through FireWire ports for capture and editing of digital video signals.
This document provides an overview of analog video fundamentals, including:
- How a video picture is generated through scanning an electrical signal across a display.
- The differences between interlaced and progressive scanning systems.
- How video resolution is specified, both in terms of visual resolution and format resolution.
- Common video formats including NTSC, PAL, HDTV/SDTV, VGA, and XGA, and their characteristics.
- The three main types of analog video interfaces: composite, S-video, and component.
This document discusses multimedia concepts including audio encoding, video encoding, and digital formats. It provides information on how audio is converted to digital form through sampling and quantization. Key video encoding concepts covered include luminance, chrominance, resolution, and frame rate. Common audio formats like WAV, AIFF, and video formats like MPEG, AVI are also summarized. The document concludes that a lack of standardization across formats has made building multimedia systems more challenging.
The document is a project report on the television system. It discusses fundamentals of monochrome and color TV systems including picture formation, number of TV lines per frame, resolution, brightness, contrast, and color composite video signals. It also covers color television topics such as additive color mixing, color difference signals, bandwidth requirements, color carrier modulation, and chroma vectors. Finally, it discusses the PAL color encoding system, audio video chains in TV stations, and DTH broadcasting including downlink and uplink chains.
The document discusses various approaches for streaming stored audio and video over the internet. It describes:
1. Using a web server, which allows simple downloading of compressed files but requires fully downloading before playback.
2. Using a web server with a metafile, which provides information to the media player to access the audio/video file, reducing download time.
3. Using a separate media server, as web servers are designed for TCP, while streaming requires UDP for improved performance without retransmissions. The media player accesses the audio/video file from the media server.
Video and television systems work by presenting a sequence of images rapidly enough that the human eye perceives them as continuous motion. Different regions use different television standards that determine aspects like the number of lines, frames per second, and color systems. Video compression codecs like MPEG remove spatial and temporal redundancy to greatly reduce file sizes for storage and transmission while maintaining adequate quality.
Multimedia elements (like audio or video) are stored in media files.
The most common way to discover the type of a file, is to look at the file extension.
Multimedia files have formats and different extensions like: .wav, .mp3, .mp4, .mpg, .wmv, and .avi.
This document provides an overview of high-definition television (HDTV). It describes HDTV as a digital television format with higher resolution of 720p or 1080i and a wider 16:9 aspect ratio compared to standard definition. The document discusses HDTV transmission standards, including MPEG-2 compression, and the components of HDTV transmitters and receivers. It concludes that HDTV will provide a significantly improved television viewing experience over traditional analog formats once implementation is complete.
A presentation covering some basic aspects of digital video data and the compression of video images. The ATSC system architecture is shown using the OSI 7-layer model from data communication theory. Video compression techniques are briefly covered.
This document presents a system for 3D TV broadcasting and distribution that is compatible with existing 2D TV systems. The aim is to develop a system that can deliver stereoscopic image pairs to mobile and home users based on digital multimedia broadcasting (DMB) and digital video broadcasting - handheld (DVB-H) standards. It discusses encoding and transmitting left and right views of 3D video using these standards in a way that maintains backward compatibility with 2D receivers. The system is designed to support 3D content on mobile devices and televisions in both broadcast and high definition formats.
The document discusses different types of data compression techniques. It explains that compression reduces the size of data to reduce bandwidth and storage requirements when transmitting or storing audio, video, and images. It describes how compression works by exploiting redundancies in the data as well as properties of human perception. Various compression methods are outlined, including lossless techniques that preserve all information as well as lossy methods for audio and video that can tolerate some loss of information. Specific algorithms discussed include Huffman coding, run-length coding, LZW coding, and arithmetic coding. The document also provides details on JPEG image compression and MPEG video compression standards.
The document discusses different types of data compression techniques. It explains that compression reduces the size of data to reduce bandwidth and storage requirements when transmitting or storing audio, video, and images. It describes how compression works by exploiting redundancies in the data as well as properties of human perception. Various compression methods are outlined, including lossless techniques that preserve all information as well as lossy methods for audio and video that can tolerate some loss of information. Specific algorithms discussed include Huffman coding, run-length coding, LZW coding, and arithmetic coding. The document also provides details on JPEG image compression and MPEG video compression standards.
The document discusses various topics related to video, including how video works, different video formats and standards, and considerations for using video in multimedia projects. It explains that video places the greatest demands on hardware and requires compression to be practical. Digital video has replaced analog and compression standards like MPEG are used to reduce file sizes while still providing reasonable quality playback. Key aspects like frame rates, resolution, aspect ratios, and safe zones are discussed for different video formats and integrating video with computer displays.
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Chapter 3 - Fundamental Concepts in Video and Digital Audio.ppt
1. Chapter 3
Fundamental Concepts in Video Digital Audio
3.1 Types of Video Signals
3.2 Analog Video
3.3 Digital Video
3.4 Digitization of Sound
3.5 MIDI
3.6 Quantization and Transmission of Audio
Wachemo University
College of Computing and Informatics
Department of Software Engineering
2. 3.1 Types of Video Signals
Component video
Higher-end video systems make use of three separate video signals
for the red, green, and blue image planes. Each color channel is sent
as a separate video signal.
(a) Most computer systems use Component Video, with separate signals
for R, G, and B signals.
(b) For any color separation scheme, Component Video gives the best
color reproduction since there is no “crosstalk” between the three
channels.
(c) However, requires more bandwidth and good synchronization of the
three components.
Multimedia Systems (Jitendra Singh)
3. Composite Video — 1 Signal
Color (“chrominance”) and intensity (“luminance”) signals are mixed into a
single carrier wave.
a) Chrominance is a composition of two color components (I and Q, or U and V).
b) In NTSC TV, e.g., I and Q are combined into a chroma signal, and a color
subcarrier is then employed to put the chroma signal at the high-frequency end
of the signal shared with the luminance signal.
c) The chrominance and luminance components can be separated at the receiver
end and then the two color components can be further recovered.
d) When connecting to TVs or VCRs, Composite Video uses only one wire and
video color signals are mixed, not sent separately. The audio and sync signals
are additions to this one signal.
• Since color and intensity are wrapped into the same signal, some interference
between the luminance and chrominance signals is inevitable.
Multimedia Systems (Jitendra Singh)
4. S-Video — 2 Signals
As a compromise, (separated video, or Super-video, e.g., in S-VHS) uses
two wires, one for luminance and another for a composite chrominance
signal.
• As a result, there is less crosstalk between the color information and the
crucial gray-scale information.
• The reason for placing luminance into its own part of the signal is that black-
and-white information is most crucial for visual perception.
– In fact, humans are able to differentiate spatial resolution in grayscale images
with a much higher acuity than for the color part of color images.
– As a result, we can send less accurate color information than must be sent for
intensity information — we can only see fairly large blobs of color, so it makes
sense to send less color detail.
Multimedia Systems (Jitendra Singh)
5. 3.2 Analog Video
• An analog signal f(t) samples a time-varying image. So-called
“progressive” scanning traces through a complete picture (a frame)
row-wise for each time interval.
• In TV, and in some monitors and multimedia standards as well,
another system, called “interlaced” scanning is used:
a) The odd-numbered lines are traced first, and then the even-numbered
lines are traced. This results in “odd” and “even” fields — two fields
make up one frame.
b) In fact, the odd lines (starting from 1) end up at the middle of a line
at the end of the odd field, and the even scan starts at a half-way point.
Multimedia Systems (Jitendra Singh)
6. Fig. 3.1: Interlaced raster scan
c) Figure 3.1 shows the scheme used. First the solid (odd) lines are traced, P to Q, then
R to S, etc., ending at T; then the even field starts at U and ends at V.
d) The jump from Q to R, etc. in Figure 3.1 is called the horizontal retrace, during
which the electronic beam in the CRT is blanked. The jump from T to U or V to P
is called the vertical retrace.
Multimedia Systems (Jitendra Singh)
7. • Because of interlacing, the odd and even lines
are displaced in time from each other —
generally not noticeable except when very fast
action is taking place on screen, when blurring
may occur.
Multimedia Systems (Jitendra Singh)
8. NTSC Video
NTSC (National Television System Committee)
Mostly used in North America and Japan.
Uses the familiar 4:3 aspect ratio (i.e., the ratio
of picture width to its height)
Uses 525 scan lines per frame at 30 fps.
Follows the interlaced scanning system, and each
frame is divided into two fields, with 262.5
lines/field.
Uses the YIQ color model
Multimedia Systems (Jitendra Singh)
9. Vertical retrace takes place during 20 lines
reserved for control information at the beginning
of each field. Hence, the number of active video
lines per frame is only 485.
Similarly, almost 1/6 of the raster at the left side
is blanked for horizontal retrace and sync. The
non-blanking pixels are called active pixels.
The horizontal retrace takes 10.9 μsec
Multimedia Systems (Jitendra Singh)
10. • Fig. 3.3 shows the effect of “vertical retrace & sync” and
“horizontal retrace & sync” on the NTSC video raster.
Fig. 3.3: Video raster, including retrace and sync data
Multimedia Systems (Jitendra Singh)
11. NTSC video is an analog signal with no fixed horizontal resolution.
Therefore one must decide how many times to sample the signal for
display: each sample corresponds to one pixel output.
A “pixel clock” is used to divide each horizontal line of video into
samples. The higher the frequency of the pixel clock, the more samples
per line there are.
Different video formats provide different numbers of samples per line, as
listed in Table 3.1.
Table 3.1: Samples per line for various video formats
Format Samples per line
VHS 240
S-VHS 400-425
Betamax 500
Standard 8 m 300
Hi-8 mm 425
Multimedia Systems (Jitendra Singh)
12. PAL Video
PAL (Phase Alternating Line)
Widely used in Western Europe, China, India,
and many other parts of the world.
Uses 625 scan lines per frame, at 25 fps
Has a 4:3 aspect ratio and interlaced fields.
YUV color model is used
Multimedia Systems (Jitendra Singh)
13. SECAM Video
Système Electronique Couleur Avec Mémoire
Uses 625 scan lines per frame, at 25 fps
With a 4:3 aspect ratio and interlaced fields.
SECAM and PAL are very similar. They differ slightly
in their color coding scheme:
(a) In SECAM, U and V signals are modulated using separate
color subcarriers at 4.25 MHz and 4.41 MHz respectively.
(b) They are sent in alternate lines, i.e., only one of the U or V
signals will be sent on each scan line.
Multimedia Systems (Jitendra Singh)
14. • Table 3.2 gives a comparison of the three major analog
broadcast TV systems.
Table 3.2: Comparison of Analog Broadcast TV Systems
Multimedia Systems (Jitendra Singh)
TV System
Frame
Rate
(fps)
# of
Scan
Lines
Total
Channel
Width
(MHz)
Bandwidth
Allocation (MHz)
Y I or U Q or V
NTSC 29.97 525 6.0 4.2 1.6 0.6
PAL 25 625 8.0 5.5 1.8 1.8
SECAM 25 625 8.0 6.0 2.0 2.0
15. 3.3 Digital Video
• The advantages of digital representation for video are
many. For example:
(a) Video can be stored on digital devices or in memory, ready
to be processed (noise removal, cut and paste, etc.), and
integrated to various multimedia applications;
(b) Direct access is possible, which makes nonlinear video
editing achievable as a simple, rather than a complex, task;
(c) Repeated recording does not degrade image quality;
(d) Ease of encryption and better tolerance to channel noise.
Multimedia Systems (Jitendra Singh)
16. Chroma Subsampling
Chroma subsampling is the practice of encoding images by
implementing less resolution for chroma information than
for luma information, taking advantage of the human visual
system's lower acuity for color differences than for
luminance.
It is used in many video encoding schemes – both analog and
digital – and also in JPEG encoding.
(a) The chroma subsampling scheme “4:4:4” indicates
that no chroma subsampling is used: each pixel’s Y, Cb
and Cr values are transmitted, 4 for each of Y, Cb, Cr.
Multimedia Systems (Jitendra Singh)
17. (b) The scheme “4:2:2” indicates horizontal subsampling
of the Cb, Cr signals by a factor of 2. That is, of four
pixels horizontally labelled as 0 to 3, all four Ys are
sent, and every two Cb’s and two Cr’s are sent, as
(Cb0, Y0)(Cr0, Y1)(Cb2, Y2)(Cr2, Y3)(Cb4, Y4), and
so on (or averaging is used).
(c) The scheme “4:1:1” subsamples horizontally by a
factor of 4.
(d) The scheme “4:2:0” subsamples in both the
horizontal and vertical dimensions by a factor of 2.
Theoretically, an average chroma pixel is positioned
between the rows and columns as shown Fig.3.4.
Multimedia Systems (Jitendra Singh)
18. Sampling systems and ratios
The subsampling scheme is commonly expressed as a three
part ratio J:a:b (e.g. 4:2:2) or four parts if alpha channel is
present (e.g. 4:2:2:4), that describe the number of
luminance and chrominance samples in a conceptual region
that is J pixels wide, and 2 pixels high. The parts are (in
their respective order):
J: horizontal sampling reference (width of the conceptual
region). Usually, 4.
a: number of chrominance samples (Cr, Cb) in the first
row of J pixels.
b: number of changes of chrominance samples (Cr, Cb)
between first and second row of J pixels.
Alpha: horizontal factor (relative to first digit). May be
omitted if alpha component is not present, and is equal
to J when present
Multimedia Systems (Jitendra Singh)
20. CCIR Standards for Digital Video
Consultative Committee for International Radio
produced CCIR-601, for component digital video.
– This standard has since become standard ITU-R-601, an
international standard for professional video applications
— adopted by certain digital video formats including the popular DV
video.
• Table 3.3 shows some of the digital video specifications,
all with an aspect ratio of 4:3. The CCIR 601 standard
uses an interlaced scan, so each field has only half as
much vertical resolution (e.g., 240 lines in NTSC).
Multimedia Systems (Jitendra Singh)
21. • CIF stands for Common Intermediate Format
specified by the CCITT (International
Telegraph and Telephone Consultative
Committee).
(a) The idea of CIF is to specify a format for lower
bitrate.
(b) CIF is about the same as VHS quality. It uses a
progressive (non-interlaced) scan.
Multimedia Systems (Jitendra Singh)
22. (c) Note, CIF is a compromise of NTSC and PAL in
that it adopts the ‘NTSC frame rate and half of the
number of active lines as in PAL.
Table 3.3: Digital video specifications
Multimedia Systems (Jitendra Singh)
CCIR 601
525/60
NTSC
CCIR 601
625/50
PAL/SECAM
CIF QCIF
Luminance resolution 720 x 480 720 x 576 352 x 288 176 x 144
Chrominance resolution 360 x 480 360 x 576 176 x 144 88 x 72
Color Subsampling 4:2:2 4:2:2 4:2:0 4:2:0
Fields/sec 60 50 30 30
Interlaced Yes Yes No No
23. HDTV (High Definition TV)
• The main thrust of HDTV (High Definition TV) is not to increase the
“definition” in each unit area, but rather to increase the visual field
especially in its width.
• HDTV is a television system providing an image resolution that that is of
substantially higher resolution than that of standard-definition television.
(a) The first generation of HDTV was based on an analog technology developed
by Sony and NHK in Japan in the late 1970s.
(b) MUSE (MUltiple sub-Nyquist Sampling Encoding) was an improved NHK
HDTV with hybrid analog/digital technologies that was put in use in the 1990s.
It has 1,125 scan lines, interlaced (60 fields per second), and 16:9 aspect ratio.
(c) Since uncompressed HDTV will easily demand more than 20 MHz bandwidth,
which will not fit in the current 6 MHz or 8 MHz channels, various
compression techniques are being investigated.
(d) It is also anticipated that high quality HDTV signals will be transmitted using
more than one channel even after compression.
Multimedia Systems (Jitendra Singh)
24. • A brief history of HDTV evolution:
(a) In 1987, the FCC decided that HDTV standards must be compatible with the
existing NTSC standard and be confined to the existing VHF (Very High
Frequency) and UHF (Ultra High Frequency) bands.
(b) In 1990, the FCC announced a very different initiative, i.e., its preference for a
full-resolution HDTV, and it was decided that HDTV would be simultaneously
broadcast with the existing NTSC TV and eventually replace it.
(c) Witnessing a boom of proposals for digital HDTV, the FCC made a key
decision to go all-digital in 1993. A “grand alliance” was formed that included
four main proposals, by General Instruments, MIT, Zenith, and AT&T, and by
Thomson, Philips, Sarnoff and others.
(d) This eventually led to the formation of the ATSC (Advanced Television
Systems Committee) — responsible for the standard for TV broadcasting of
HDTV.
(e) In 1995 the U.S. FCC Advisory Committee on Advanced Television Service
recommended that the ATSC Digital Television Standard be adopted.
Multimedia Systems (Jitendra Singh)
25. • The standard supports video scanning formats shown in
Table 3.4. In the table, “I” mean interlaced scan and “P”
means progressive (non-interlaced) scan.
Table 3.4: Advanced Digital TV formats supported by
ATSC
Multimedia Systems (Jitendra Singh)
# of Active
Pixels per line
# of Active
Lines
Aspect Ratio Picture Rate
1,920 1,080 16:9 60I 30P 24P
1,280 720 16:9 60P 30P 24P
704 480 16:9 & 4:3 60I 60P 30P 24P
640 480 4:3 60I 60P 30P 24P
26. • For video, MPEG-2 is chosen as the compression
standard. For audio, AC-3 is the standard. It supports the
so-called 5.1 channel Dolby surround sound, i.e., five
surround channels plus a subwoofer channel.
• The salient difference between conventional TV and
HDTV:
(a) HDTV has a much wider aspect ratio of 16:9 instead of 4:3.
(b) HDTV moves toward progressive (non-interlaced) scan. The
rationale is that interlacing introduces serrated edges to
moving objects and flickers along horizontal edges.
Multimedia Systems (Jitendra Singh)
27. • The FCC has planned to replace all analog
broadcast services with digital TV broadcasting
by the year 2009. The services provided will
include:
– SDTV (Standard Definition TV): the current NTSC
TV or higher.
– EDTV (Enhanced Definition TV): 480 active lines or
higher, i.e., the third and fourth rows in Table 3.4.
– HDTV (High Definition TV): 720 active lines or
higher.
Multimedia Systems (Jitendra Singh)
28. 3.4 Digitization of Sound
What is Sound?
• Sound is a wave phenomenon like light, but is
macroscopic and involves molecules of air being
compressed and expanded under the action of some
physical device.
(a) For example, a speaker in an audio system vibrates back
and forth and produces a longitudinal pressure wave that we
perceive as sound.
(b) Since sound is a pressure wave, it takes on continuous
values, as opposed to digitized ones.
Multimedia Systems (Jitendra Singh)
29. (c) Even though such pressure waves are
longitudinal, they still have ordinary wave
properties and behaviors, such as reflection
(bouncing), refraction (change of angle when
entering a medium with a different density)
and diffraction (bending around an obstacle).
(d) If we wish to use a digital version of sound
waves we must form digitized representations
of audio information.
Multimedia Systems (Jitendra Singh)
30. Digitization
• Digitization means conversion to a stream of
numbers, and preferably these numbers should
be integers for efficiency.
• Fig. 3.5 shows the 1-dimensional nature of
sound: amplitude values depend on a 1D
variable, time. (And note that images depend
instead on a 2D set of variables, x and y).
Multimedia Systems (Jitendra Singh)
31. Fig. 3.5: An analog signal: continuous measurement
of pressure wave.
Multimedia Systems (Jitendra Singh)
32. • The graph in Fig. 3.5 has to be made digital in both time and
amplitude. To digitize, the signal must be sampled in each
dimension: in time, and in amplitude.
(a) Sampling means measuring the quantity we are interested in,
usually at evenly-spaced intervals.
(b) The first kind of sampling, using measurements only at evenly
spaced time intervals, is simply called, sampling. The rate at
which it is performed is called the sampling frequency (see Fig.
3.6(a)).
(c) For audio, typical sampling rates are from 8 kHz (8,000 samples
per second) to 48 kHz. This range is determined by the Nyquist
theorem, discussed later.
(d) Sampling in the amplitude or voltage dimension is called
quantization. Fig. 3.6(b) shows this kind of sampling.
Multimedia Systems (Jitendra Singh)
33. Fig. 3.6: Sampling and Quantization. (a): Sampling the
analog signal in the time dimension. (b): Quantization is
sampling the analog signal in the amplitude dimension.
Multimedia Systems (Jitendra Singh)
(a) (b)
34. • Thus to decide how to digitize audio data we
need to answer the following questions:
1. What is the sampling rate?
2. How finely is the data to be quantized, and is
quantization uniform?
3. How is audio data formatted? (file format)
Multimedia Systems (Jitendra Singh)
35. • Nyquist Theorem: If a signal is band-limited, i.e., there
is a lower limit f1 and an upper limit f2 of frequency
components in the signal, then the sampling rate should
be at least 2(f2 − f1).
• Nyquist frequency: half of the Nyquist rate.
– Since it would be impossible to recover frequencies higher
than Nyquist frequency in any event, most systems have an
antialiasing filter that restricts the frequency content in the
input to the sampler to a range at or below Nyquist
frequency.
• The relationship among the Sampling Frequency, True
Frequency, and the Alias Frequency is as follows:
falias = fsampling − ftrue, for ftrue < fsampling < 2 × ftrue
Multimedia Systems (Jitendra Singh)
36. Signal to Noise Ratio (SNR)
• The ratio of the power of the correct signal and the noise
is called the signal to noise ratio (SNR) — a measure
of the quality of the signal.
• The SNR is usually measured in decibels (dB), where 1
dB is a tenth of a bel. The SNR value, in units of dB, is
defined in terms of base-10 logarithms of squared
voltages, as follows:
Multimedia Systems (Jitendra Singh)
2
10 10
2
10log 20log
signal signal
noise noise
V V
SNR
V V
37. a) The power in a signal is proportional to the
square of the voltage. For example, if the
signal voltage Vsignal is 10 times the noise,
then the SNR is 20 ∗ log10(10) = 20dB.
b) In terms of power, if the power from ten
violins is ten times that from one violin
playing, then the ratio of power is 10dB, or
1B.
Multimedia Systems (Jitendra Singh)
38. • The usual levels of sound we hear around us are described in terms of
decibels, as a ratio to the quietest sound we are capable of hearing. Table 3.5
shows approximate levels for these sounds.
Table 3.5: Magnitude levels of common sounds, in decibels
Multimedia Systems (Jitendra Singh)
Threshold of hearing 0
Rustle of leaves 10
Very quiet room 20
Average room 40
Conversation 60
Busy street 70
Loud radio 80
Train through station 90
Riveter 100
Threshold of discomfort 120
Threshold of pain 140
Damage to ear drum 160
39. Signal to Quantization Noise Ratio
(SQNR)
• Aside from any noise that may have been present
in the original analog signal, there is also an
additional error that results from quantization.
(a) If voltages are actually in 0 to 1 but we have only 8
bits in which to store values, then effectively we force
all continuous values of voltage into only 256 different
values.
(b) This introduces a round off error. It is not really
“noise”. Nevertheless it is called quantization noise
(or quantization error).
Multimedia Systems (Jitendra Singh)
40. • The quality of the quantization is characterized
by the Signal to Quantization Noise Ratio
(SQNR).
(a) Quantization noise: the difference between the
actual value of the analog signal, for the
particular sampling time, and the nearest
quantization interval value.
(b) At most, this error can be as much as half of the
interval.
Multimedia Systems (Jitendra Singh)
41. (c) For a quantization accuracy of N bits per sample, the SQNR can
be simply expressed:
• Notes:
(a) We map the maximum signal to 2N−1 − 1 (≃ 2N−1) and the most
negative signal to −2N−1.
(b)The above equation is the Peak signal-to-noise ratio, PSQNR: peak
signal and peak noise.
Multimedia Systems (Jitendra Singh)
1
2
20log 20log
10 10 1
_
2
20 log 2 6.02 (dB)
V N
signal
SQNR
V
quan noise
N N
42. Audio Filtering
• Prior to sampling and AD conversion, the audio signal is also usually
filtered to remove unwanted frequencies. The frequencies kept depend
on the application:
(a) For speech, typically from 50Hz to 10kHz is retained, and other
frequencies are blocked by the use of a band-pass filter that screens
out lower and higher frequencies.
(b) An audio music signal will typically contain from about 20Hz up to
20kHz.
(c) At the DA converter end, high frequencies may reappear in the output —
because of sampling and then quantization, smooth input signal is
replaced by a series of step functions containing all possible frequencies.
(d) So at the decoder side, a low pass filter is used after the DA circuit.
Multimedia Systems (Jitendra Singh)
43. Audio Quality vs. Data Rate
• The uncompressed data rate increases as more bits are used
for quantization. Stereo: double the bandwidth. to transmit
a digital audio signal.
Table 3.6: Data rate and bandwidth in sample audio applications
Multimedia Systems (Jitendra Singh)
Quality Sample Rate
(Khz)
Bits per
Sample
Mono /
Stereo
Data Rate
(uncompressed)
(kB/sec)
Frequency Band
(KHz)
Telephone 8 8 Mono 8 0.200-3.4
AM Radio 11.025 8 Mono 11.0 0.1-5.5
FM Radio 22.05 16 Stereo 88.2 0.02-11
CD 44.1 16 Stereo 176.4 0.005-20
DAT 48 16 Stereo 192.0 0.005-20
DVD Audio 192 (max) 24(max) 6 channels 1,200 (max) 0-96 (max)
44. Synthetic Sounds
Digitized sound must still be converted to analog, for us to hear
it. There are two fundamentally different approaches to handling
stored sampled audio.
1. FM (Frequency Modulation): one approach to generating synthetic
sound:
2. Wave Table synthesis: A more accurate way of generating sounds from
digital signals. Also known, simply, as sampling.
In this technique, the actual digital samples of sounds from real instruments
are stored. Since wave tables are stored in memory on the sound card, they
can be manipulated by software so that sounds can be combined, edited,
and enhanced.
Multimedia Systems (Jitendra Singh)
45. 3.5 MIDI: Musical Instrument Digital
Interface
• A protocol that enables computer, synthesizers, keyboards,
and other musical device to communicate with each other.
• This protocol is a language that allows interworking between
instruments from different manufacturers by providing a link
that is capable of transmitting and receiving digital data.
• Transmits only commands, it does not transmit an audio
signal.
• It was created in 1982.
Multimedia Systems (Jitendra Singh)
46. Components of a MIDI System
1. Synthesizer:
It is a sound generator (various pitch, loudness, tone color).
A good (musician’s) synthesizer often has a microprocessor, keyboard,
control panels, memory, etc.
2. Sequencer:
It can be a stand-alone unit or a software program for a personal computer.
(It used to be a storage server for MIDI data).
Nowadays it is more a software music editor on the computer.)
It has one or more MIDI INs and MIDI OUTs.
Multimedia Systems (Jitendra Singh)
47. Basic MIDI Concepts
Track:
Track in sequencer is used to organize the recordings.
Tracks can be turned on or off on recording or playing back.
Channel:
Channels are used to separate information in a MIDI system.
There are 16 MIDI channels in one cable.
Channel numbers are coded into each MIDI message.
Timbre:
The quality of the sound, e.g., flute sound, cello sound, etc.
Multitimbral – capable of playing many different sounds at the
same time (e.g., piano, brass, drums, etc.)
Multimedia Systems (Jitendra Singh)
48. Pitch:
The musical note that the instrument plays
Voice:
Voice is the portion of the synthesizer that produces
sound.
Synthesizers can have many (12, 20, 24, 36, etc.)
voices.
Each voice works independently and simultaneously
to produce sounds of different timbre and pitch.
Patch:
The control settings that define a particular timbre.
Multimedia Systems (Jitendra Singh)
49. MIDI to WAV Conversion
• Some programs, such as early versions of
Premiere, cannot include .mid files — instead,
they insist on .wav format files.
a) Various shareware programs exist for approximating a
reasonable conversion between MIDI and WAV
formats.
b) These programs essentially consist of large lookup
files that try to substitute pre-defined or shifted WAV
output for MIDI messages, with inconsistent success.
Multimedia Systems (Jitendra Singh)
50. 3.6 Quantization and Transmission of Audio
• Coding of Audio: Quantization and transformation of
data are collectively known as coding of the data.
a) For audio, the μ-law technique for companding audio
signals is usually combined with an algorithm that exploits
the temporal redundancy present in audio signals.
b) Differences in signals between the present and a past time
can reduce the size of signal values and also concentrate
the histogram of pixel values (differences, now) into a
much smaller range.
Multimedia Systems (Jitendra Singh)
51. c) The result of reducing the variance of values is
that lossless compression methods produce a bit
stream with shorter bit lengths for more likely
values.
• In general, producing quantized sampled output
for audio is called PCM (Pulse Code
Modulation). The differences version is called
DPCM (and a crude but efficient variant is
called DM). The adaptive version is called
ADPCM.
Multimedia Systems (Jitendra Singh)
52. Pulse Code Modulation
• The basic techniques for creating digital signals
from analog signals are sampling and
quantization.
• Quantization consists of selecting breakpoints
in magnitude, and then re-mapping any value
within an interval to one of the representative
output levels.
Multimedia Systems (Jitendra Singh)
53. Fig. 3.2: Sampling and Quantization.
Multimedia Systems (Jitendra Singh)
(a) (b)
54. a) The set of interval boundaries are called decision
boundaries, and the representative values are called
reconstruction levels.
b) The boundaries for quantizer input intervals that will
all be mapped into the same output level form a coder
mapping.
c) The representative values that are the output values
from a quantizer are a decoder mapping.
d) Finally, we may wish to compress the data, by
assigning a bit stream that uses fewer bits for the most
prevalent signal values.
Multimedia Systems (Jitendra Singh)
55. • Every compression scheme has three stages:
A. The input data is transformed to a new
representation that is easier or more efficient to
compress.
B. We may introduce loss of information. Quantization is
the main lossy step ⇒ we use a limited number of
reconstruction levels, fewer than in the original signal.
C. Coding. Assign a codeword (thus forming a binary
bitstream) to each output level or symbol. This could
be a fixed-length code, or a variable length code such
as Huffman coding.
Multimedia Systems (Jitendra Singh)
56. PCM in Speech Compression
• Assuming a bandwidth for speech from about 50 Hz to about 10 kHz,
the Nyquist rate would dictate a sampling rate of 20 kHz.
(a) Using uniform quantization without companding, the minimum sample
size we could get away with would likely be about 12 bits. Hence for
mono speech transmission the bit-rate would be 240 kbps.
(b) With companding, we can reduce the sample size down to about 8 bits
with the same perceived level of quality, and thus reduce the bit-rate to
160 kbps.
(c) However, the standard approach to telephony in fact assumes that the
highest-frequency audio signal we want to reproduce is only about 4
kHz. Therefore the sampling rate is only 8 kHz, and the companded bit-
rate thus reduces this to 64 kbps.
Multimedia Systems (Jitendra Singh)
57. Fig. 3.7: Pulse Code Modulation (PCM). (a) Original analog signal and
its corresponding PCM signals. (b) Decoded staircase signal. (c)
Reconstructed signal after low-pass filtering.
Multimedia Systems (Jitendra Singh)
58. • The complete scheme for encoding and decoding
telephony signals is shown as a schematic in Fig. 3.8.
As a result of the low-pass filtering, the output becomes
smoothed and Fig. 3.7(c) above showed this effect.
Fig. 3.8: PCM signal encoding and decoding.
Multimedia Systems (Jitendra Singh)
Editor's Notes
DM (Delta Modulation): simplified version of DPCM. Often used as a quick AD converter.
• Differential PCM is exactly the same as Predictive Coding, except that it incorporates a quantizer step