Index for Multimedia Technology Development Process Multimedia Software Calculating Graphic File Sizes Types of Graphic File Streaming Digitised Pictures

Index for Multimedia Technology

Development Process

Multimedia Software

Calculating Graphic File Sizes

Types of Graphic File

Streaming

Digitised Pictures

Codecs

Digitised Sound

Calculating Sound File Sizes

Synthesised Sound

Digitised Video

Calculating Video File Size

Connecting to Peripherals

File Compression

© Steve Clulow BSc, Greenfaulds High School, Cumbernauld

Development Process

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Analysis

Design

Implementation

Testing

Documentation

Evaluation

Maintenance

Work out what needs doing. End result is Requirements Specification & Technical Specification.

Storyboarding – shows content, layout and navigation links for the Multimedia application.

Use of Multimedia authoring and Web Page Authoring packages to implement the storyboard designs.

Check all hyperlinks to ensure navigation works, also that layout is correct and that final product works as expected from remote site (web pages)

User Guide (for specialist Multimedia if required) and Technical Guide showing hyperlink relationships, specifying minimum transfer rates.

Evaluate the final product against the initial Requirements and Technical specifications.

Adapting / modifying the Multimedia application to suit changing client needs and emerging technologies.

Multimedia Software – Web Page Creation Software

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Presentations

Sound Editing

Text Editors

Examples: Notepad & Wordpad

Allows the programmer direct access to the html code to add extra functionality i.e. via java script.

Need to know what you are doing. Difficult to judge complex layouts this way!

Used by professional web designers!

WYSIWYG: What you see is what you get

Example: Dream Weaver

Allows user to layout pages like a word processing / desk top publishing application.

Quick results, but limited functionality without ability to access the html code direct.

Ideal for non professionals!C

Normal to use both: WYSIWYG for initial layout – Text Editor to add extra functionality

Authoring software to create multimedia applications: Examples – Director (mainly script based,

have more control over effects), Hyperstudio (mainly icon based, simple to use)

Web Page Development Software

Video Editing

Multimedia Software – Video Editing Software


Timeline View

Examples: Camtasia Studio, Movie Maker

Allows user to click & drag video, sound and graphics and adjust the length (time) played in the final presentation.

Can also add Title Clips and callouts.

Storyboard View

Example: Camtasia Studio, Movie Maker

Shows individual clips in sequence allowing the addition of transitional effects between clips such as fade out, fade in etc.

Also allows user to add effects to clips such as making black / white, aged etc.

Video Editing Software

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Presentations

Sound Editing

Web Page Editing

Multimedia Software – Sound Editing Software


Over amplification has caused clipping (flattening) of sound waves at upper & lower bounds!

Sound Editing

Example: Audacity

• Open files (Stereo 2 channels, Mono 1 channel)

• Highlight areas to delete (cut) unwanted bits

• Adjust ends with Fade In / Fade Out

• Add effects to sounds

• Can copy and paste sounds together to produce mixed track

• If Over amplified will cause “Clipping” and will distort sound badly!

• Can save final track as CD, MP3, Wav etc.

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Presentations

Web Page Editing

Video Editing

Multimedia Software – Presentation Software


Presentation Software

Example: Microsoft PowerPoint

• Presentations consist of a series of slides

• Slides can incorporate Multimedia elements, such as text,

graphics, sound and video.

• Elements and slide transitions can have animation effects

added.

• You can also add hyperlinks to produce complex

navigational structure giving multiple pathways

• Most modern Presentation packages also give the facility to

save presentations directly into web ready formats.

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Web Page Editing

Sound Editing

Video Editing

Streaming

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This technique enables users to access large multimedia files, such as audio and video, quickly by allowing them to play the file before all of the data has arrived.

Play rate needs to be slower than the transfer rate to operate smoothly!

Streaming follows several steps:

1. Data to be streamed is “Compressed”

2. Server sends data as a series of packets

3. As data packets arrive computer decompresses / decodes and sends to a buffer

4. Data then sent to sound / video card and processed using DSP and DAC

5. Software downloads a few seconds of data into buffer before playing

6. If contents of buffer used before next part of stream arrives then get pauses / missed sections

Types of Streaming:

Live Streaming: Stream data as it is generated. Takes a lot of processing due to need to compress in real time.

Almost Live Streaming: Stream with built in delays to allow for compression process.

File Streaming: Transmitting a file that has already been compressed

Pseudo-streaming: Same as file streaming, but allows user to view after first portion of data is received i.e. 15% (Examples Google video, You Tube)

Embedded Files: Multimedia embedded directly into html and saved with it. Becomes part of the page.

Codecs

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Codec - Compression / Decompression

Codecs are used to compress binary data to reduce file sizes to enable faster transmission over networks / reduce amount of backing storage required to store the data.

Most codecs use algorithms to compress / decompress the files. Audio and Video applications are also used (such as Dix X avi video codec. Can get a full movie down to around 700 Mb)

You cannot use any codec file in every application. For instance PowerPoint will not recognise DivX video, but will recognise .wmv and some other standard avi codecs.

Container Files

A container file can hold several compressed files. When the container file is transmitted a program is needed at the receiving end to regenerate the separate files held within it.

A Zip file is an example of a container file (WinZip uses the LZW algorithm to get lossless data compression)

http://images.google.co.uk/imgres?imgurl=http://www.lifeboatdistribution.com/Content/images/promotions_2007/Winzip/winzip-icon.gif&imgrefurl=http://www.lifeboatdistribution.com/redir.aspx%3Fciid%3D455%26cachename%3Dadvertising%26PageGroupId%3D17%26url%3D%255E%255E%255EWinZip%255E%255E%255EDefault.aspx%253Fname%253Dwinziphome%255E%255E%255E&h=88&w=90&sz=6&hl=en&start=10&tbnid=vxBw5Nt316jCKM:&tbnh=76&tbnw=78&prev=/images%3Fq%3Dwinzip%2Bicon%26gbv%3D2%26svnum%3D10%26hl%3Den%26sa%3DG

Digitised Pictures - Hardware

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Scanners & Cameras

1. Light reflected onto row of photo sensitive CCDs (Charged Couple Device)

(Note: one row for black / white, three rows for colour R,G,B, array of CCD for cameras, Video cameras use 3 CCD arrays and a beam splitter to split light into RGB components)

2. Each CCD produces a different voltage depending on the amount of light detected

3. ADC (Analogue to Digital Conversion) takes place

4. DSP (Digital Signal Processor) streams out digital values to backing storage

(may apply compression such as jpeg in digital cameras, mpeg to videos)

Cameras store files onto solid state devices (memory cards), where as Video Cameras tend to store onto Magnetic Tape, DVD discs or built in Hard Drives.

Hardware

CLUT (Colour Look Up Table): used by graphics applications to allow user to specify subset of colours to be used

Calculating Graphic File Sizes

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You will need to be able to calculate file sizes for bitmap graphics using the relationship

File Size = (height in pixels x Width in pixels) x Colour Depth

Example:

Given a 10” x 8” true colour graphic scanned at 600 dpi calculate the file size

Step 1: True colour uses 24 bits (3 bytes) per pixel

Step 2: Height in pixels = 10 x 600 = 6000

Step 3: Width in pixels = 8 x 600 = 4800

Step 4: File size in bytes = 6000 x 4800 x 3 = 8,640,000 bytes

Step 5: 8,640,000 / 1024 = 84,375 Kb

Step 6: 84,375 / 1024 = 82.4 Mb

Remember Colour depth can be 8 bits (1 byte) – GIF & PNG 16 bits (2 bytes) 24 bit (3 bytes) – True Colour

Types of Graphic File – Picture Formats

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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld© Steve Clulow BSc, Greenfaulds High School, Cumbernauld

24 Bit True Colour

Excellent Quality, can be manipulated at pixel level.

Resolution dependant (pixilation) and very large file sizes

GIF (Graphics Interchange Format)

8 bit (1 byte) per pixel therefore only 256 colour palette. Good for cartoons / line drawings with limited colours. Can set transparent backgrounds (single bit transparency), Can be non interlaced (scan in line by line) or Interlaced (Blurred then sharpen). Can be animated. Utilises LZW lossless compression.

JPEG (Joint Photographic Expert Group)

Millions of colours available, favourite format for cameras. Uses complex algorithm to achieve lossy compression (a compression setting of about 60% will result in the optimum balance of quality and filesize,). Very small file sizes. Can be interlaced.

PNG (Portable Network Graphics)

Much like GIF with PNG-8 having 256 colours, supports data streaming, can be interlaced and has transparency feature. PNG-24 has full colour capabilities and holds an alpha value for opacity. Uses lossless compression.

Dithering &Anti-Aliasing

3D Vectors

Types of Graphic File – 3D Vectors

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Dithering &Anti-Aliasing

3D Vector Graphics

As with normal vectors data is recorded as mathematical values for position, line thickness, fill colour etc.

Now also need to record depth, angle of rotation, surface texture and shadow / position of light source.

Some standard formats include:

SVG (Scaleable Vector Graphics)

e.g. Cube{ Width 20, Height 20, Depth 20}

Cylinder {Radius 20, Height 150}

Sphere {Radius 20}

VRML (Virtual Reality Markup Language)

WRL (World Description Language)

You need a plug in for browsers to display them.

Picture Formats

Dithering & Anti-Aliasing

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3D Vectors

Dithering

Dithering is used to create the impression of more colours than the colour palette / bit depth can represent by putting dots of two or more colours close together to create another colour.

Look at the two examples opposite. The first has only black and white dots, but gives the impression of grey scale and the second has gone from the millions of colours available to 24bits down to 8 bits (256 colours), but still looks similar

Anti - Aliasing

Anti – Aliasing is used to “smooth” the edges of images by blending the edges into the background image. Otherwise you end up with a jagged white line around it.

Picture Formats

Digitised Sound – How sound is recorded

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Sound is an ANALOGUE signal recorded as differing voltages that can be at any level at any given time. These voltages cause electro magnets in speakers to vibrate, recreating the sound waves to hit our eardrums.

But computers only understand DIGITAL signals (o or 1, 5v or 0v) so the analogue signals have to be changed into a binary format.

This is done by taking sample values and recording the voltage values as binary numbers over a given time.

The number of bits used to record these values can effect the quality of the recording (8 bits only allows for 256 states, 16 bits allow for 65536 states)

Obviously there is a need for ADC (Analogue to Digital Conversion) to send digitally recorded music to speakers, as well as DAC (Digital to Analogue Conversion) for recording sound via microphones. This is carried out by SOUND CARD hardware. DSP (Digital Signal Processing) is also carried out.

Sound Terminology

How Sound is Recorded

Digitised Sound – Sound Terminology

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Bit Rate: bits per second required to transmit sound (CD 1378 kbps, MP3 384 kbps)

PCM (Pulse Code Modulation): Method of encoding signal by varying the amplitude of pulses.

RIFF (Resource Interchange File Format): file format that can contain bitmap graphics, animation, digital audio and MIDI files. Wav file format is the RIFF format for storing sound data.

ADPCM (Adaptive Delta Pulse Code Modulation): Compressed PCM data. Only stores changes between samples and not samples themselves. Used in WAV format (either 8 or 16 bit depth with sample rates of 11.025 kHz, 22.05 kHz or 44.1 kHz)

Normalisation: Signal levels of different sounds adjusted to average volume

Clipping: Over Amplification causes data loss at peaks / troughs distorting the sound.

Sound Terminology

How Sound isRecorded

Calculating Sound File Sizes

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You will need to be able to calculate sound file sizes using the formula

File Size = Sampling Frequency (Hz) x Time (s) x Depth (bytes) x Channels

(NB: Mono has One Channel Stereo has Two channels)

Example:

Calculate the file size of one minute of Mono sound sampled at 22.05 kHz anda bit depth of 8 bits

Step 1: 22.05 kHz = 22050 Hz

Step 2: 8 bits = 1 byte

Step 3: Mono = 1 channel

Step 4: 1 minute = 60 seconds

File Size = 22050 x 60 x 1 x 1 = 1323000 bytes = 1292 Kb = 1.26 Mb

Synthesised Sound

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MIDI (Musical Instrument Digital Interface)

• Used to digitally record instruments like keyboards, synthesisers and drum machines.

• Holds information on Instrument, pitch, volume, duration and tempo

• You can save messages generated by many instruments in one file

• Produces very small file sizes

• Can be edited with a text editor

• Used for ring tones on older mobile phones.

• Browsers need plug in to play MIDI files

Digitised Video – File Formats

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AVI (Audio Video Interleave)

Limited file size: 2 Gb

Resolution: 320 x 240

Frame rate: 30 frames per second

Original Microsoft product for use in Windows Media player. Now superseded by Windows Media Video (WMV) as this supports Mpeg 4 compression.

MOV

Apple (Mac) QuickTime video format.

Better Quality than standard uncompressed AVI

Smaller file sizes

Now can be used for steaming video with apple QuickTime player, as well as use on mobile devices.

MPG (Motion Picture Experts Group)

MPEG 1(PAL) Resolution: 352 x 288, 25 Fps

MPEG 2(PAL) Resolution 720 x 576 , 25 Fps

MPEG 2(NTCS) Resolution 720 x 480, 30 Fps

MPEG 2 is standard format for DVD storing a 2 hour film into a few Gb. Now have MPEG 4 that is basis of WMV and can be used for recording video for High End TV use and mobile devices

Lossy compression by use of key frames and recording changes in between key frames

DV (Digital Video)

Also mini DV, DVPro and DVCam

Digital formats for use with digital camcorders

Data rates of 25 to 100 Mbps

Compression Ratio of 5:1

Utilises Intraframe Compression

Calculating Video File Size

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You will need to be able to calculate file sizes for videos using the formula

File Size = (height in pixels x Width in pixels) x Colour Depth x Frame Rate (s) x length (s)

Example:

What is the uncompressed file size of a 30 second video recorded at 25 frames per second. The video resolution is 640 x 480 and it was shot in 24 bit true colour.

Step 1: True colour uses 24 bits (3 bytes) per pixel

Step 2: Height in pixels = 480

Step 3: Width in pixels = 640

Step 4: File size in bytes = 480 x 640 x 3 x 25 x 30 = 691200000 bytes

Step 5: 691200000 / 1024 = 675000 Kb

Step 6: 84,375 / 1024 = 659.2 Mb

Techniques to reduce file size:

Reduce Frame Rate (causes flicker below 22)

Reduce Colour Depth (loss of quality)

Reduce Resolution (smaller image)

Crop / Cut image (reduced picture)

Connecting to Peripherals

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USB (Universal Serial Bus)

Link Multiple devices via one port (max 127)

Fast Transfer Rates (USB 1 max 12 Mbps)

(USB 2 max 480 Mbps)

Plug and Play (no reconfiguration required)

Max distance 5 meters

Firewire

Link multiple devices via one port (max 63)

Fast Transfer Rates (800 Mbps – 3.2 Gbps)

Distances up to 100 meters (fibre optic cable)

WiFi

Used to connect LANs (home & office)

Fast Transfer Rates 11 Mbps – 54 Mbps

Max distance 30m

Bluetooth

Wireless connection of mobiles / peripherals

Link Multiple devices via one port (max 8)

Fast Transfer Rates 720 Kbps – 10 Mbps

Can carry digital voice / data transmission

Max distance 10m to 100m (with booster)

Developments inTechnology

MultimediaHardware

Developments in Technology

Sound Card

Needs to carry out ADC / DAC

ADC (Analogue to Digital Conversion)

When converting Analogue input from Microphone into Digital recording of Analogue voltage levels / time as binary values.

DAC (Digital to Analogue Conversion)

When sending Digitally recorded voltage levels to speakers the stored values need to be converted back to an Analogue voltage to make the electromagnets in the speakers vibrate.

Graphics Card

Needs to carry out ADC / DAC / DSP

ADC (Analogue to Digital Conversion)

When converting Analogue input from TV video into digitally stored data about each frame

DAC (Digital to Analogue Conversion)

When transmitting digitally stored values back to a device that only understands Analogue signal. i.e. CRT Monitor, TV etc.

DSP (Digital Signal Processing)

May be required to compress / decompress digital data file and store data in correct sequence. Card may have own processor / RAM

NIC (Network Interface Card)

Provides the physical connection and electronics to connect a computer to a Local Area Network. Converts data into a form that can be transmitted across the network.

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Developments inTechnology

Connecting toPeripherals

Developments in Technology

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Connecting toPeripherals

Holographic Storage

Provides high storage densities of approx. 10 Gb per cubic centimetre and has very fast access time. Like all optical discs it uses lasers to read / write but throughout the whole thickness of the disc in three dimensions.

3D Display Technology

Real 3D display: Old fashioned now with use of Red / blue lenses for pictures / cinema

Virtual 3D display: For use with Virtual Reality systems, goggles or helmet

Flat Panel displays: TFT (Thin Film Transistor) taking over from LCD. Sharper images / colours

3D Flat Panel displays: Three major new technologies

Parallax Illumination – creates two images with same data, each eye recieves different image to create 3d effect.

Beam Splitter Sheet – sits in front of LCD, refracts light to create 3d image

Multiple Layers – uses multiple layers of LCD screens to create 3d effect

Main Uses: Simulators, Research Projects, Image Processing MultimediaHardware

File Compression

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Needed to reduce file sizes for faster transmission over networks and reduce storage requirements

Lossless

Data is encrypted to reduce file size by applying LZW algorithm

Two files created – Dictionary and Data file

Need to transmit both as need dictionary to reassemble data file, but no data lost (get original)

Lossy

Complex algorithms used to reduce file size. Data lost cannot be retrieved

Examples:

JPEG: Cuts out aspects of graphic information that will not be noticed by the human eye. It uses a quality percentage indicator (100 % excellent – 0% grey sludge) and compression rates of 20:1 produces little noticable loss.

MP3: Used on sound files, MP3 achieves compreesion by filtering out aspects of original sound that the human ear will not notice, such as only recording the louder of two sounds. It then uses Huffman Encoding to further compress the file (I min = 1Mb)

Documents

Index for Multimedia Technology Development Process Multimedia Software Calculating Graphic File Sizes Types of Graphic File Streaming Digitised Pictures