Transcript Multimedia - Greenfaulds High School

Index for Multimedia Technology
Development Process
Digitised Sound
Multimedia Software
Calculating Sound File Sizes
Streaming
Synthesised Sound
Codecs
Digitised Video
Digitised Pictures
Calculating Video File Size
Calculating Graphic File Sizes
Connecting to Peripherals
Types of Graphic File
File Compression
© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Development Process
Work out what needs doing. End result is Requirements Specification & Technical
Specification.
Analysis
Storyboarding – shows content, layout and navigation links for the Multimedia
application.
Design
Implementation
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)
Testing
Documentation
User Guide (for specialist Multimedia if required) and Technical Guide
showing hyperlink relationships, specifying minimum transfer rates.
Evaluation
Maintenance
Evaluate the final product against the initial Requirements and
Technical specifications.
Adapting / modifying the Multimedia application to suit
changing client needs and emerging technologies.
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Multimedia Software – Web
Page Creation Software
Web Page Development Software
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
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!
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)
© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Video Editing
Sound Editing
Presentations
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Multimedia Software – Video
Editing 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.
Web Page Editing
Sound Editing
Presentations
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Multimedia Software – Sound
Editing Software
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.
Over amplification has caused
clipping (flattening) of sound
waves at upper & lower
bounds!
Video Editing
Web Page Editing
Presentations
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
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.
Video Editing
Sound Editing
Web Page Editing
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Streaming
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.
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Codecs
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)
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Digitised Pictures - Hardware
Hardware
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.
CLUT (Colour Look Up Table): used by graphics applications to allow user to specify subset of colours to be used
© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
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Calculating Graphic File Sizes
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
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Types of Graphic File – Picture
Formats
GIF (Graphics Interchange Format)
24 Bit True Colour
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.
Excellent Quality, can be manipulated at
pixel level.
Resolution dependant (pixilation) and
very large file sizes
JPEG (Joint Photographic Expert Group)
PNG (Portable Network Graphics)
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.
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.
©©Steve
SteveClulow
ClulowBSc,
BSc,Greenfaulds
GreenfauldsHigh
HighSchool,
School,Cumbernauld
Cumbernauld
3D Vectors
Dithering &
Anti-Aliasing
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Types of Graphic File – 3D
Vectors
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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©©Steve
SteveClulow
ClulowBSc,
BSc,Greenfaulds
GreenfauldsHigh
HighSchool,
School,Cumbernauld
Cumbernauld
Dithering & Anti-Aliasing
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
3D Vectors
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©©Steve
SteveClulow
ClulowBSc,
BSc,Greenfaulds
GreenfauldsHigh
HighSchool,
School,Cumbernauld
Cumbernauld
Digitised Sound – How sound is
recorded
How Sound is Recorded
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
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Digitised Sound – Sound
Terminology
Sound Terminology
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.
How Sound is
Recorded
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Calculating Sound File Sizes
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
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Synthesised Sound
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
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Digitised Video – File Formats
AVI (Audio Video Interleave)
MOV
Limited file size: 2 Gb
Apple (Mac) QuickTime video format.
Resolution: 320 x 240
Better Quality than standard uncompressed
AVI
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.
MPG (Motion Picture Experts Group)
Smaller file sizes
Now can be used for steaming video with
apple QuickTime player, as well as use on
mobile devices.
DV (Digital Video)
MPEG 1(PAL) Resolution: 352 x 288, 25 Fps
Also mini DV, DVPro and DVCam
MPEG 2(PAL) Resolution 720 x 576 , 25 Fps
Digital formats for use with digital camcorders
MPEG 2(NTCS) Resolution 720 x 480, 30 Fps
Data rates of 25 to 100 Mbps
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
Compression Ratio of 5:1
Utilises Intraframe Compression
Lossy compression by use of key frames and
recording changes in between key frames
© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
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Calculating Video File Size
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)
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Connecting to Peripherals
USB (Universal Serial Bus)
Bluetooth
Link Multiple devices via one port (max 127)
Wireless connection of mobiles / peripherals
Fast Transfer Rates
(USB 1 max 12 Mbps)
Link Multiple devices via one port (max 8)
(USB 2 max 480 Mbps)
Fast Transfer Rates 720 Kbps – 10 Mbps
Plug and Play (no reconfiguration required)
Can carry digital voice / data transmission
Max distance 5 meters
Max distance 10m to 100m (with booster)
Firewire
WiFi
Link multiple devices via one port (max 63)
Fast Transfer Rates
(800 Mbps – 3.2 Gbps)
Distances up to 100 meters (fibre optic cable)
Used to connect LANs (home & office)
Fast Transfer Rates 11 Mbps – 54 Mbps
Max distance 30m
Multimedia
Hardware
Developments in
Technology
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
Developments in Technology
Graphics Card
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.
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.
Connecting to
Peripherals
Developments in
Technology
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Developments in Technology
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
Multimedia
Hardware
Connecting to
Peripherals
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld
File Compression
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)
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© Steve Clulow BSc, Greenfaulds High School, Cumbernauld