sound and multi media

7/27/2019 sound and multi media

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Multimedia Elements

Sound, Animation, and

Video


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Sound

Analog wave patterns these wave

patterns have two attributes

Volume the height of each peak in the sound

wave

Frequency (sometimes referred to as pitch)

the distance between the peaks. The greater

the distance, the lower the sound.

Image: scanned from Multimedia Concepts James Schuman


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Sampling

To include sound in a multimedia

application, the sound waves must beconverted from analog to digital form

This conversion is called sampling every

fraction of a second a sample the of soundis recorded in digital bits


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Sampling

Two factors affect the quality of digitized

sound

1) Sample rate the number of times the sampleis taken

Most common sampling rates are: 11.025, 22.05,

and 44.1 kHz

2) Sample size the amount of information

stored about the sample

Most common sampling sizes are: 8 and 16 bit


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Sampling



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Sound File Formats

WAV formatfilename.wav

AIFF (Audio Interchange File Format)

AIFFC (compressed)RealAudio filename.ra

MP3 (mpeg layer 3)


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Sound on the Internet

Your first consideration when using sound

on the Internet is file size

Uncompressed files can be very largeA 10 second recording of an audio CD can be

as large as 2MB


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Sound Tips for the Internet

Appropriate

Use

Consider the appropriateness of using sound. Some

sounds are content-related, such as hearing a foreign

phrase pronounced. Other sounds are for effect, such

as creating a mood or setting a scene. Avoid using

sound when there is no compelling benefit.

Quality Start with the highest-quality sound available and

reduce the file size by converting the audio file to a

compressed format. When possible, avoid using free

sound clips available from the Internet. These are often

of poor quality and overused.

Cost

considerations

When recording audio files, it may be cost-prohibitive to

contract with a recording studio and hire professional

talent. Investing in reasonably high-end equipment

(such as a sound card, microphone, and recording and

editing software), however, will prove worthwhile.


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Sound Tips for the Internet

Alternative

Methods

Consider using sound and still images as an alternative to

video to reduce file sizes. It may be just as effective to

show a photograph of a speaker and play the sound file of

the speech as it is to show a video of a talking head.

Streaming Consider streaming the audio, especially for large files.

User

Control

If appropriate, provide a way to give the user some

control over the audio. Consider allowing the user to skip

a sound clip or adjust the volume. This issue is especially

important if a musical introduction is played when the user

first enters a Web site. The second time visiting the site,

the user may not want to hear the musical introduction.


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Animation on the Internet

Animation is an excellent way to provide

appeal on a web site, choose from the

following

Animated text

Animated GIFsMarcomedia Director applications

3-D environments


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2-D Animation

Two types of animation exist

Cel animation based on changes that occur

form one frame to the next

Path animation moves an object along a

predetermined path on the screen


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3-D Animation

3-D Animation involves three steps

1) Modeling creating the broad contours and

structure of 3-D objects and scenes

2) Animationdefining the objects motion

3) Rendering giving objects attributes such as

color, surface textures, and amounts of

transparency


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3-D Animation



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3-D Animation Special Effects

Morphing blending together two images

into a series of images

Warping distorts a single image

Virtual Reality creates an environmentthat surrounds the user so that he or she

becomes part of the experience


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Animation

Animated text using the HTML

command causes text to flash on and off

Animated gif using a software programto create a series of gif files such as GIF

Builder

Director movie animation played usingShockwave plug-in

3-D environments a computer language

used to create 3-D images


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Design Considerations

Give the user control over whether or notto display or enlarge graphic images

Allow the user to be active while graphicimages are being displayed

Provide feedback to the user by displayingthe amount of time a file will take todownload


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Video

Video, like sound, is recorded and played

an as analog signal

Analog video must be digitized in order for

it to put into a multimedia file

Digital video has many advantages, but

file size is important


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Video

Several elements determine file size:

Frame rate

Image size

Color depth

To determine file size use the following

formula:Frames per second X image size X color depth

/ 8 = file size


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Video Compression and Editing

There are two types of video compression

Lossless preserves the exact image

throughout the compression

Lossy eliminates some of the data in the

image (provides greater compression ratios

than lossless)

Remember there is always a trade off, file

size versus image quality


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Video on the Internet

There are two types of video transfer over

the Internet

HTTP (Hypertext Transfer Protocol)downloads the entire video to the hard drive on

the users computer

RTSP (Real-Time Streaming Protocol) is acontinuous-playing, streaming technology in

which the users computer is in constant contact

with the server playing the video


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Video Tips

Color

depth

Reducing the color depth to less than 256 colors

gives a markedly poorer-quality image.

Frame

rate

Reducing the frame rate to less than 15 frames

per second causes a noticeable and distractingjerkiness that is usually unacceptable.

File size A technique for reducing file size is to minimize

the use of video in the image that appears on

the screen that is, to create video only for theparts of an object that are changing, such as a

flickering candle. The video could be played over

and over to create the motion of a flickering

candle.


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Video Tips

Display size In most multimedia titles, you do not need

to show full-screen video. The video can

be played in a window that can be as

small as one-fourth or even one-sixteenththe size of the screen.

Conclusion: Changing the image size and compressing

the file become the primary ways of reducing file size. Inmost cases, a one-quarter screen image (320 X 240), an 8-

bit (256 colors) color depth, and a 15 frames per second

frame rate are acceptable in a multimedia title.


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The End

University of North Texas

Dr. Vicky Cereijo

sound and multi media

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