audio video animation-5

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DIGITAL AUDIO IN MULTIMEDIADIGITAL AUDIO IN MULTIMEDIA


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Objective

What is sound?

Waveforms and attributes of sound

Capturing digital audio Sampling

MIDI (Musical Instrument Digital Interface)


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Sound

Sound comprises the spoken word, voices, music andeven noise.

It is a complex relationship involving a vibratingobject

(sound source), a transmissionmedium (usually air), areceiver(ear) and a perceptor(brain).

Example banging drum.

As the sound vibrates it bumps into molecules of the

surrounding medium causing pressure waves to travelaway from the source in all directions

So, Sound are rapid vibrations that aretransmitted as variations in air pressure.


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Waveforms

Sound waves are manifest as waveforms

A waveform that repeats itself at regular intervals is

called a periodic waveform

Waveforms that do not exhibit regularity are callednoise

The unit of regularity is called a cycle

This is known as Hertz (orHz) after Heinrich Hertz One cycle = 1 Hz

Sometimes written as kHz orkiloHertz (1 kHz =

1000 Hz)


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Waveforms

distance

along waveCycle

Time for one cycle


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The CharacteristicsofSoundWaves

Sound is described in terms of two characteristics:

Frequency

Amplitude (or loudness)

Frequency

The rate at which sound is measured

Number of cycles per second or Hertz (Hz)

Determines the pitch of the sound as heard by ourears

The higher frequency, the clearer and sharper thesoundthe higher pitch of sound


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Amplitude

Sounds intensity or loudness

The louder the sound, the larger amplitude.

In addition, all sounds have a duration and successive

musical sounds is called rhythm


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distance

along wave

Cycle

Time for one cycleAmplitude

pitch


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1111

Capture & Playbackof Digital Audio

Air pressure

variations

Captured via

microphone

Air pressure

variations

ADC

Signal is

converted into

binary

(discrete form)0101001101

0110101111

Analogueto DigitalConverter

DACConvertsback into

voltage

Digital toAnalogueConverter


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Sampling

Two parameters:

1. Sampling Rate

Frequency of sampling

Measure in Hertz

The higher sampling rate, higher quality sound but size storage

is big.

Standard Sampling rate:

- 44.1 KHz for CD Audio- 22.05 KHz

- 11.025 KHz for spoken

- 5.1025 KHz for audio effect


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Sampling

2. Size sample

The resolution of a sample is the number of bits it uses

to store a given amplitude value, e.g.

8 bits (256 different values)

16 bits (65536 different values)

A higher resolution will give higher quality but will require more

memory (or disk storage)


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Calculating the Size of Digital Audio

The formula is as follows:

The answer will be in bytes

Where:

sampling rate is in Hz

Duration/time is in seconds

resolution is in bits (1 for8 bits, 2 for 16 bits)

number of channels = 1 for mono, 2 for stereo, etc.

8

channelsofnumberresolutiondurationrate vvv


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Example:

Calculate the file size for 1 minute, 44.1 KHz, 16 bits,stereo sound

Where:

sampling rate is 44,100 Hz

Duration/time is 60 seconds

resolution is 16 bits

number of channels for stereo is 2

8



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8


44100 * 60 * 16 *2

8

10584000 bytes


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Digital Audio EditingSoftware

One of the most powerful and professional PC-based

packages is a tool called SoundForge


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Editing Digital Audio

Trimming

Splicing and assembly

Volume adjustments

Format conversion

Resampling or downsampling

Fade ins and fade outs

Equalization

Time Stretching

Digital Signal processing

Reversing Sounds


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Editing Digital Audio

Simple audio editing software allows:

Recording of digital audio segments

Trimming

Splicing and assembly

Volume adjustments of the entire segment

Reversing Sounds

Copy, cut, paste and delete segments of digital audio

Others audio editing software: COOLEdit Pro

Gold Wave

PROSONIQ SonicWORX

Samplitude Studio


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AudioFormats

Depend on O/S. For examples:

AIFF (Audio Interchange File Format)

SOU

For Macintosh

.WAV

Waveform file format. For Windows/Microsoft

.VOC

Sound Blaster Card


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MIDI

(Musical Instrument Digital Interface)

MIDI is a standard for specifying a musical performance

Rather than send raw digital audio, it sends instructions

to musical instruments telling them what note to play, atwhat volume, using what sound, etc.(soundsequencer)

The synthesiserthat receives the MIDI events is

responsible for generating the actual sounds. Example: Keyboard Piano


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MIDI Sequencers A MIDI sequencerallows musicians to edit and create

musical compositions like a word processor Cut and paste

Insert / delete


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MIDI VersusWav

Quality recording, MIDI depend to the tools

Audio .wav easier to create compare than MIDI

MIDI Advantages File Size small

Size Storage also small

MIDI Disadvantages Playback

Cost and Skill


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How Audio can be used effectively

Examples of uses of audio:

Cautions andwarningsIt is a good medium for alerting users to critical

information. Some uses include:

Sounding an alarm when a limit is reached

Alerting users when data is entered

incorrectly


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Music andSound Effects

These make multimedia interaction more real. Some

uses include:

Musical background for a video segment

Birds Songs accompanying photographs in biological field

training.

Sound-relateddata.

Some uses include: Helping mechanics diagnose engine trouble

Training medical students to recognize different

breathing sounds


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Direct voice communication.

Some uses include:

Leaving a voice message for other users of an

application

Consulting with an expert during a troubleshooting

procedure.


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Advantages & Disadvantagesofusing

Audio

Sound adds life to any multimedia application and plays

important role in effective marketing presentations.

Advantages

Ensure important information is noticed

Add interest

Can communicate more directly than other media


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Advantages & Disadvantagesofusing

Audio

Disadvantages

Easily overused

Requires special equipment for quality production

Not as memorable as visual media

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Lecture 3: Video

DIGITAL VIDEO IN MULTIMEDIADIGITAL VIDEO IN MULTIMEDIA


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Analogue video

What is digital video?

Calculating the size of digital video

Compression techniques

Digital video formats

Video capture hardware

Digital video editing

Consumer desktop video

Objective


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Analog 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 signalknown as an analogue wave form or composite video.

Composite analogue video has all the video

components: brightness, colour and synchronization

Then, combined into one signal for delivery


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Analog video

Usage : television

Problems: colour blending, low clarity, high generation

lost, difficult to edit


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Type of Analogue VideoSignal

There are two main analogue video formats

PAL and NTSC

PAL (Phase Alternate Line)

standard television format used in the European, UK,

Australia and South Africa

Consist 625 scan lines drawn every 1/25 second


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Type of Analogue VideoSignal

NTSC, NationalTelevision System Committee, is the American andJapanese standard

Consist of 525 scan lines drawn every 1/30 second

Television usually has a 4:3 aspect ratio

For every 1 pixel down there are 1.333 pixels across

Aspect ratio is the comparison of width to height for a

viewing area

Digital TV has an aspect ratio of 16:9 (wide screen)


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What isdigital video?

Digital video is the digitisation of analogue video

signals into numerical format

It creates the illusion of full motion by displayinga rapid sequence of changing images on a

display device.


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File Size Considerations

Several elements determine the file size, in additional tothe length of the video. These including:

Frame rate

Number of images displayed within a specifiedamount of time to convey a sense of motion

Usually measured in frames per second

Standard video movie 30 fps, movie film 24 fps

Video digital at least 15 fps


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Frame or Image size

width and height of each individual frame or image

Determines the quality of the image displayed and theprocessing involved to display that image

Standard full screen resolution is 640x480 pixels

Video screen display is one fourth the size of the full

window screen (320x240)


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Colordepth/Resolution

Number of colors displayed on the screen at one time

Ranging from 1 bit to 8 bit, 16 or 24 bit per pixel

Quality directly related to frame size, image size and

color depth.

Qualitiy also depends on content. Motion picture needs

higher frame rate


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Calculating the Size of Digital Video

Where:

Frame size = image size ( width * height in pixels)

Frame rate = frames per second

Color depth = measured in bytes

time = time in seconds

Thisdoesnot include any sounddata !Thisdoesnot include any sounddata !

File size = frame size * frame rate * Color Depth * time


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Compression Techniques

Since the size of raw digital video is so prohibitively largewe need some means to compress the information

Video compression and decompression program, known

as Codecs

Lossy compression techniques cause someinformation to be lost from the original image

Redundant information Example: Image and video

JPEG and MPEG

Intraframe and Interframe


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Compression Techniques

Lossless compression techniques do not lose

information throughout the compression and

decompression process

Example use in text images

Exactly same before and after compression

Technique is to identify repeating words and assign

them a code.

Decompression, the code would be changed back to

the actual word.


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Digital VideoFormats

MPEG / MJPEG

Files with a .mpg extension

Apple QuickTime

Files with a .mov or.qt extension

Microsoft AVIFiles with a .avi extension


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MPEG Video

Named after the Moving Picture Experts Group who

devised the compression and file formats

There are a number of MPEG formats:

MPEG-1 is a format used for low quality video(generally displayed on computers)

MPEG-1 Layer3 is the popular encoding

mechanism for MP3 audio

MPEG-2 is used for digital TV broadcasts and DVDs MPEG-4 is a new format for multimedia presentations

Can require separate hardware to decode higher quality

MPEG video data


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MPEG Compression Example

A simple scene showing a car moving

across a desert landscape

Only the difference

between the current

and next frame needs

to be stored

This is called intraframe coding


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QuickTime

Developed by Apple, Inc.

Primarily for playback without any hardware

assistance

Can achieve compression ratios of 25 to 200:1

The QuickTime format can also store audio,

graphics, 3D and text making it more much versatile

for multimedia applications


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Microsoft AVI

Audio Video Interleave format

Interleaving is a technique used to embed two or more

things into the same stream of information

In every chunk of information you will find some videodata and some audio data

001001010010010101010011110101...

001001010010010101010011110101...

...

001001010010010101010011110101...

001001010010010101010011110101...

Video

information

Audio

information

8, 16

or24

bits


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Digital Video Editing

Analogue tape editing is a linear process

To find the section you want, you may have to forward

or rewind the video tape

To move a section to another place in the sequence

you have to either re-record the section onto another

tape or physically cut andsplice the video tape


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Digital Video Editing

Digital video editing can be non-linear process

You can move sections around inside the computer

and play those sections back in any order


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How Video can be used effectively

Example of uses for video

Showing physical procedures. Some uses are:

Installing a board in a PC

Adjusting engine timing

Attracting and holding attention. Some uses are:

Advertising products and services

Teaching new skills to busy employees


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How Video can be used effectively

Presentingscenarios. Some uses are:

Training technicians to respond to equipment

malfunctions

Demonstrating possible uses for a product

Analyzingmotion . Some uses are:

Body motion to improve athletic performance

Traffic patterns for transportation planning


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Advantages and Disadvantages

ofusing video

Video adds visual impact to multimedia applications:

Advantages

Captures interest

Increase retention

Clarifies complex physical actions and relationships

Can incorporate other media


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ofusing video

Disadvantages

Is expensive to produce

Requires extensive memory and storage

Requires special equipment

Does not effectively illustrate abstract concepts andstatic situations

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DIGITAL ANIMATION IN MULTIMEDIADIGITAL ANIMATION IN MULTIMEDIA


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What is an animation?

Animation categories

Animation Special Effects

Objective


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Animation

Such animation is made from a series of stillsand relies on something calledpersistence of

vision.

Persistence of vision is the phenomenon

were an object on the eyes retina remains for

a brief time after viewing.

This means that a series of still images which

vary slightly, if shown rapidly will give the

illusion of movement.


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Animation

If each of the eight pictures below were

shown at the same point in rapid succession,

the result would be a rotating arrow.

The pictures shown below are stills of therotating Ford logo from the Ford Motor

Company site.


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Animation

TV gives the illusion of continuous movement byshowing the stills at the rate of 30 frames per second.

Feature films are filmed at a rate of 24 frames persecond but shown at a rate of 48 frames per second.

Today, most animation is performed by computer.

Examples are Bugs, Toy Story, Jurassic Park etc.

The computer will produce a wire frame of the scene,

then apply textures and light effects before moving ontothe production of the next frame, each of which may takehours or even days to produce.


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Animation Categories

Two categories :

Traditional Animation

All frame in an animation had to be drawn byhand

Computer Graphics Animation The use of computers to create animations.


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Traditional Animation

Different techniques for creating animation by

hand:

Key frames

Cell Animation

Rotoscoping: An animation technique for

tracing images of live action, often a part of

motion capture


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Computer Graphics Animation

Two types of Computer Graphics:

Linear animationor2D animation

Page flipping

Cell Animation

Object Animation or Path Animation

3D animation Modelling

Rendering


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AnimationSpecial Effects: Morphing

Morphing is the effect in which one imagetransforms into anotherthrough a series ofintermediate frames.

This is done by first creating or scanning the

first and last images.

Then key points are specified, i.e. points onthe original image which should becomepoints on the final image.

The computer then produces the frames inbetween, with each successive framebecoming progressively more morphed intothe last image.


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Morphing

The creator can usually specify the number ofintermediate frames to be produced as well

the the number of key points.

Both the number of the key points and

number of frames will impact on the time

taken to produce the sequence of frames.


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Morphing

Morphing software: Photo Morph,

Hijact Morph

Elastic Reality

The diagrams show start and end frames and the intermediate

frames produced by morphing software


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AnimationSpecial Effects:Warping

Special effect that allows you to manipulate asingle image.

Example:

You could stretch a facial feature to

change a frown into a smile.

Warping software : Kai Super Goo


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ofusing Animation

Disadvantages

Requires extensive memory and storage space

Requires special equipment for a quality presentation

Cannot depict actuality like video or photography

audio video animation-5

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