multimedia elements: sound, animation, and video

Multimedia Elements: Sound, Animation, and Video

Objectives

Describe the sound, animation, and video elements that make up multimedia

Specify the tradeoffs involved in using these elements

Specify the advantages and disadvantages of using these elements

Describe the programs used with these elements

Multimedia Elements: Sound, Animation, and Video 3

Chapter Outline

Sound• Sampling• MIDI

Animation Video

• Digitizing• Compression


Sound

Volume: height of peak Frequency: distance between peaks,

measured in hertz (Hz)

Volume

Frequency


Sampling

A digital representation of a portion of the sound is made every fraction of a second.

Sample rate: how often is the digital representation made?

Sample size: how large (# of bits) is each digital representation?• Number of bits used for each sample• or, the number of quantization levels


Sample Rate

Common sample rates• 11.025 kHz• 22.05 kHz• 44.1 kHz

The more samples, the more accurately the sound is represented

The more samples, the larger the file size


Sample Size

Common sample sizes• 8 bit: 256 possible values• 16 bit: 65,536 possible values

The larger the sample size, the more accurately the sound is represented

The larger the sample size, the larger the file size


File Size

1 second = sample rate x bit value / 8 Stereo doubles the size CD quality: 44.1khz 16 bit sample Stereo CD-quality file size: 176,400 bytes

per second


Sound Card

Used to digitize sound Accepts analog input from audio source Samples according to specified sample rate

and sample size Produces digital representation of the audio

signal


Sound Editing Programs

Digital representations can be easily manipulated

Cut and paste Sound effects (echo, fade-in, fade-out, etc.)


MIDI

Musical Instrument Digital Interface MIDI files

• Coded events (such as note pitch and duration)• Series of instructions that can be followed by

any MIDI-capable musical instrument• Another way to incorporate sound into

multimedia titles


MIDI Compared to Digital Audio

Digitized audio begins with a sound, samples it, and creates a digital representation which is stored in a file.

MIDI begins with an event, such as pressing a key on an electronic musical instrument such a s MIDI keyboard, and code the event (including which key and how hard and long it was pressed) as a series of commands.


MIDI Compared to Digital Audio Advantages

because it represents the notes along with information as volume and frequency

• More precise editing is possible • File sizes are much smaller

Disadvantages• Only MIDI-capable instruments can send MIDI

instructions• Only MIDI-compatible playback devices can be used


MIDI Compared to Digital Audio

Requires specialized software A MIDI compatible audio card Special equipment with MIDI interface


Animation

Consists of a series of images, each in its own frame

“Jerkiness” occurs when fewer than 12 frames per second (fps) are displayed


Types of 2-D Animation

Cel animation Path animation


Cel Animation

‘Cel’ comes from the word ‘celluloid’ Objects move against a fixed background


Path Animation

Objects move along predetermined path Path specified by mouse dragging or by

clicking on intermediate points Tweening is a technique used to fill in the

path between predetermined points


Steps in 3-D Animation

Modeling Animation Rendering


Modeling

Process to create 3-D objects and scenes Points are set in a grid to define the object’s

shape


Animation

Specify the object’s motion Specify how lighting and views change as

the object moves


Rendering

Apply colors, textures, and transparency to objects

Takes a substantial amount of time


Animation Special Effects

Morphing: transform one image into another in a series of frames

Warping: transform aspects of a single image in a series of frames


Virtual Reality

Attempts to create an environment that “Surrounds” the user so that he or she becomes part of the experience

Useful for simulations, games, and educational applications

Requires that the user have a high-end computer


Digitizing Video

Video source is connected to video capture card in the computer

The card converts the video signal to a digital file stored on the hard drive


Advantages of Digital Video

Easier to edit Adding special effects is easier


File Size Considerations

Frame rate: 15 fps (low quality) to 30 fps (TV quality)

Image size: 320 x 240 (1/4 screen) to 640x480 (full screen)

Color depth: 8 bits (256 colors) to 24 bits (16 million colors)

fps x image size x color depth / 8 = file size per second


Video Compression

Codec: compression/decompression programs

Lossless compression: exact image is retained

Lossy compression: some information about the image is lost


JPEG Compression

JPEG: Joint Photographic Experts Group File size is reduced by removing redundant

information Similar neighboring pixels are stored as a

block of pixels 20:1 compression possible


MPEG Compression

MPEG: Motion Picture Experts Group Includes still-image compression Also removes redundant information

between frames Requires special hardware


Software for Capturing and Editing Video Some packages permit capturing,

compressing, and editing video Common editing features

• Fast access to any frame• Transitions• Titles• Sound-video synchronization• Filters


Key Terms

Analog wave pattern Animation Cel animation Codec Frames per second

(fps)

Frequency Hertz (Hz) JPEG Lossless compression Lossy compression MIDI


Key Terms (continued)

Modeling Morphing MPEG Path animation Rendering Sampling

Sound card Tweening Virtual reality (VR) Volume Warping

multimedia elements: sound, animation, and video

Documents

video elements

usedmultimedia elements

secondmultimedia elements

file sizemultimedia

hertz hzmultimedia elements

digital audioadvantagesbecause

digital audiodigitized

specified sample rate