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

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Presentation on theme: "Index for Multimedia Technology Development Process Multimedia Software Calculating Graphic File Sizes Types of Graphic File Streaming Digitised Pictures."— Presentation transcript:

1 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

2 Development Process Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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.

3 Multimedia Software – Web Page Creation Software Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

4 Multimedia Software – Video Editing Software © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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 Back to Index Presentations Sound Editing Web Page Editing

5 Multimedia Software – Sound Editing Software © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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. Back to Index Presentations Web Page Editing Video Editing

6 Multimedia Software – Presentation Software © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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. Back to Index Web Page Editing Sound Editing Video Editing

7 Streaming Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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.

8 Codecs Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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)

9 Digitised Pictures - Hardware Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

10 Calculating Graphic File Sizes Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

11 Types of Graphic File – Picture Formats Back to Index © 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

12 Types of Graphic File – 3D Vectors Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

13 Dithering & Anti-Aliasing Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

14 Digitised Sound – How sound is recorded Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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 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

15 Digitised Sound – Sound Terminology Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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 kHz, 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 is Recorded

16 Calculating Sound File Sizes Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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 kHz anda bit depth of 8 bits Step 1: kHz = Hz Step 2: 8 bits = 1 byte Step 3: Mono = 1 channel Step 4: 1 minute = 60 seconds File Size = x 60 x 1 x 1 = bytes = 1292 Kb = 1.26 Mb

17 Synthesised Sound Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

18 Digitised Video – File Formats Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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

19 Calculating Video File Size Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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 = bytes Step 5: / 1024 = Kb Step 6: 84,375 / 1024 = 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)

20 Connecting to Peripherals Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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 in Technology Multimedia Hardware

21 Developments in Technology Multimedia Hardware 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. Back to Index Developments in Technology Connecting to Peripherals

22 Developments in Technology Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld Connecting to Peripherals 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

23 File Compression Back to Index © Steve Clulow BSc, Greenfaulds High School, Cumbernauld 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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