MULTIMEDIA SYSTEMS

• Decibel


  Unit used to measure the intensity or loudness of sound

  
• Waveforms

  • Pleasant sound has a regular wave pattern that is repeated over and over
  • Noise has irregular waves that do not have a repeated pattern

  
• Sound


  • Described in terms of frequency (or pitch) and amplitude (or loudness)

  
• Frequency


  Measure of how many vibrations occur in one second, measured in Hertz (Hz)
• Frequency ranges

  • Optimally people can hear from 20 Hz to 20,000 Hz (20 kHz)
  • Sounds below 20 Hz are infrasonic
  • Sounds above 20 kHz are ultrasonic

  
• Amplitude


  The maximum displacement of a wave from an equilibrium position, relates to how loud a sound is

  
• Default system sounds

  • MACINTOSH - Chu Toy, Glass, indigo, Laugh, Simple Beep
  • WINDOWS PC - ding.wav, chimes.wav, logoff.wav, start.wav
• Analogue audio


  An electronic signal that carries information of sound as continuous fluctuating voltage value

  
• Digitizing

  1. The process of converting an analog signal to a digital one

  2. Sound is recorded by making a measurement of the amplitude

  3. The act of taking the measurement is called "sampling" and each measurement is called a "sample point"
• Recording audio files on PC

  1. Microphone: connect microphone to microphone port and record using sound recorder

  2. CD-ROM Drive: move music files from CD to hard drive or play CD and record using sound recorder

  3. Line-in: press play on audio source connected to computer's audio line-in socket, record using sound recorder

  
• Digital audio


  • Representation of sound stored in the form of sample points
  • Quality depends on sampling rate (number of sample points per second)
• MIDI


  • Popular format when audio is required to be put on a website
  • MIDI keyboard used to simplify creation of music scores
  • MIDI sequencer software lets us record and edit MIDI data like a word processor
• Audio formats

  • MIDI: *.MID, *.KAR, *.MIDI, *.SMF
  • WINDOWS: *.WAV
  • MACINTOSH: *.AIFF
  • UNIX: *.AU
  • REALAUDIO: *.RA
  • MPEG3: *.MP3
• Decibel levels and associated sounds

  • 40 - Raindrops
  • 60 - Normal conversation
  • 85 - busy city traffic
  • 90 - hair dryer
  • 105- rock concerts
  • 110 - chain saws
  • 115 - iPad at peak volume
  • 120 - Jack hammers
  • 140- gunshot/fireworks
• 85 DECIBELS FOR 8 HOURS A DAY
• Video


  The moving picture, accompanied by sound such as a picture in television
• Digital video


  • Useful in multimedia application for showing real life objects
• Video


  • Excellent tool for delivering multimedia
  • Places the highest performance demand on computer and its memory and storage
• Analogue Video


  • Video information that is stored using television video signals, film, videotape or other non-computer media
  • Each frame is represented by a fluctuating voltage signal known as an analogue wave form or composite video
• Composite analogue video


  • Has all the video components: brightness, color and synchronization
  • Then combined into one signal for delivery
  • Example: traditional television signal
• Progressive scan


  • Used in computer monitors and digital televisions
  • Displays all the horizontal lines of a picture at one time as a single frame
• Interlaced scan


  • Used in standard television formats
  • Displays only half of the horizontal lines at a time (the first field, containing the odd-numbered lines, is displayed, followed by the second field, containing the even-numbered lines)
• National Television Standards Committee (NTSC)


  • Standards for coding information into an electronic signal, to make a TV picture
  • US, Japan
  • Amplitude modulation
  • Frame of video: 525 vertical scan lines
  • 30 frames per second

  
• PAL


  • Phase Alternate Line
  • Europe, Australia, South Africa
  • 625 scan lines
  • 25 frames per second
• SECAM


  • Sequential Color and Memory
  • France, Russia
  • Also 625-line, 25 frames per sec, interlaced
• High Definition Television - HDTV

  • Advanced Television Systems Committee (ATSC, www.atsc.org)
  • Six video formats (resolution & frame rate combinations)
  • 16:9 aspect ratio (width:height ratio)
  • 1080 x 1920-pixels or 720 x 1280-pixels
  • 24, 30, 60 frames/sec
• File Size and Formats

  • New high-definition televisions (HDTV) are capable of resolutions up to 1920×1080p60, ─ 1920 pixels per scan line by 1080 scan lines, progressive, at 60 frames per second
  • A standard full screen resolution is 640x480 pixels but to safe storing space a video with 320x240 for a computer display is still acceptable
  • File size in digitized video which included still images
  • Television and movies play at 30 fps but acceptable playback can be achieved with 15 fps
• Video Compression

  • Lossless compression: Preserves the exact image throughout the compression and decompression process
  • Lossy compression: Eliminates some of the data in the image and therefore provides greater compression ratios than lossless compression
• Digitalizing Video


  • Video is simply moving pictures
  • Digitized video can be edited more easily
  • Digitized video files can be extremely large
  • Digital video is often used to capture content from movies and television to be used in multimedia
• Video File Formats


  • AVI Format (.avi): Developed by Microsoft, supported by Apple QuickTime Player, Microsoft Windows Media Player, VideoLAN VLC media player
  • Quicktime Format (.mov): Developed by Apple, common for internet, saving movie and video files
  • MP4 Format (.mp4): Mostly used to store audio and visual streams online, most commonly those defined by MPEG, can be played on Apple QuickTime Player or other movie players
• Special Effects


  • Transitions: Such as fading, wiping, splatters, scrolling, stipple and many more are available by simply dragging and dropping that transition between the two video clips
  • Chroma Key: The ability to superimpose one clip over another, the technique of green screening is identical except that the color green is used for the screen and later digitally removed
• Authoring for Multimedia Functionality

  • The concept of interactive design and the considerations to take to make it effective
• Features of Authoring Tools

  • Editing Features
  • Organizing Features
  • Visual programming with icons or objects
  • Programming with a scripting language
  • Document Development tools
  • Internet Playability
  • Cross-Platform Capability
  • Playback Features
• Most authoring environment and packages exhibit capabilities to create edit and transform different kinds of media that they support
• Organizing features

  The process of design and production of multimedia involve navigation diagrams or storyboarding
• Visual programming with icons or objects


  Simplest and easiest authoring process, e.g. clicking on an icon to play a sound
• Programming with a scripting language


  Authoring software offers the ability to write scripts for software to build features that are not supported by the software itself, e.g. computational tasks, sensing user input and responding, character creation, animation
• Document Development tools


  • Offer direct importing of pre-formatted text, indexing facilities, complex text search mechanisms, hypertext linking tools
• Internet Playability


  Authoring systems typically provide a means to convert their output so that it can be delivered within the context of HTML or DHTML
• Cross-Platform Capability


  Some authoring programs are available on several platforms and provide tools for transforming and converting files and programs from one to the other