"What is a multimedia system"
Multimedia What is a multimedia system Multimedia is the use of different types of media to present a message. Multimedia systems are information systems that combine different types of media. The multimedia systems involve many participants, a wide range of experiences and emphasise the information process of displaying. 1. Characteristics of MM systems Text, hypertext and numbers Text is any sequence of symbols that have a meaning. Hypertext is a text presented in such a way that when selected, new information will be displayed. Text, hypertext and numbers are the building blocks of any multimedia system. Text and numbers are the word-processed words that aid and begin communication in any information system. Hypertext is text that has hot links that enable connections to other sections of text or other characteristics within a multimedia system. The information contained is in static form to enable the reader to develop a written understanding rather than audio or visual communication. Information technology that is required for text, hypertext and numbers consists of word processors that are capable of completing the links and are effective text converters, as some data may need to be changed from ASCII code in order to be used within the multimedia system. Audio This is the sound that has been captured and converted from a sound wave (analog) into a digital form. Consideration needs to be given as to the use of audio, as the file is usually very large and will need to be compressed. Music can be stored in waveform or MIDI files. Most current sound cards support wav. as well as midi files. Images and/or animations Images are either vector or bit-mapped images. These images, which could include a photo, are said to be “static” or motionless. 1 E/kumar/multimedia system Hypermedia is the use of pictures, charts, graphs and icons, to provide linked information. Animations are images that appear to move. There are two types of animation. Cel-based animation where each cell is reproduced and variations are made to the next cell. This continues until there is a series of cells. Each cell is slightly different from the previous. It gives the appearance of movement, thus animation. All cels usually hand drawn and painted. Path-based animation where the first (original) cell or frame is drawn and the last cell or frame is drawn. The software then fills in the gaps between (tweening) these two frames, giving the appearance of movement. The background remains the same. Video Video combines pictures and sounds displayed over time. Using video in multimedia systems enables moving images in real-time to be displayed to enhance the text, audio and other graphics images. E.g. in encyclopaedias, video clips are inserted that reflect the content of the other features of the section displayed. Hyperlinks and buttons are frequently employed to activate video within the presentation. MPEG is a compressed video format that has become a standard now. QuickTime is the video and animation format developed for Apple Computers. Interactive multimedia An interactive presentation a two-way communication between the user and the presentation. A multimedia system enables the participants to create a realistic display and the ability to interact with the system. Tools such as buttons and hot spots created in applications enable the user to interact with the multimedia system. There is a need to ensure that the interactivity does not take away the meaning of the multimedia system. 2 E/kumar/multimedia system Differences between Print and Multimedia. Mode of display-print is limited to hardcopy. Where as multimedia uses computers, organisers, TV , wireless pockets Interactive –print can just be read while multimedia can give response back to the user Static and dynamic. Print media is static. It will not change unless reprinted. Multimedia is dynamic as it can be changed anytime. Indexing- in print media index is selected and few while in multimedia every word can be indexed. Data structure- in multimedia data has to be sorted to make it easily available. Or searched. Demands made on hardware Before a typical multimedia presentation is displayed it has to be reloaded from the storage device on to the frame buffer. A frame buffer is the section of memory that displays the current image seen on the screen. Large resolution images displayed using lesser memory will affect the quality of the image. Being displayed. The hardware must be capable of supplying the needs of the multimedia system. These needs are: Primary and secondary storage capabilities – which will enable bit depth and colour to be represented and also enabling the audio data to be sampled. Processing speed – which will enable video data and frames rates to be maintained, the processing of images such as morphing and distorting as well as animation. Display devices – which are capable of displaying good pixel and resolution quality. Resolution is the quality of the presented image and is described by the number of pixels across and down the screen. These pixels make up the image. Each pixel can have many shades of colour. In black and white image it can have either black or white. The bit depth describes the number of bits that is needed to store each pixel. This provides the number of possible colours for each pixel. 3 E/kumar/multimedia system Bit Depth Number of colours Relationship 1 2 21 = 2 2 4 22 = 4 Memory Sizes and display With a bit-mapped display system, the higher the resolution and number of colours used, the greater the memory size required to store the image. The memory size for a screen image can be worked out by multiplying the total number of logical pixels by the number of bits used per pixel. A screen, which displays a resolution of 800 x 600 and sixteen colours, works out as follows: Memory size = (800 x 600) x 4 bits (16 colours requires 4 bits (24 = 16)) = 480 000 x 4 bits =1 920 000 bits This can be simplified by dividing by eight to convert the bits to bytes 1 920,000 8 240,000 bytes then dividing by 1024 since there are 1024 bytes in a kilobyte. = 240 000 1024 = 235 KB 1. Complete the following table using the method set out above. Horizontal vertical Total Colours Bits per Memory resolution resolution pixels Pixel/ bit required depth 320 200 4 320 240 8 640 307200 4 1024 760 16 1024 1048576 32 4 E/kumar/multimedia system Colour can be achieved by picking from the colour palette. It is the number of colours available for the graphic image. As in paint programs. CompuServe Graphic Interchange Format (gif) uses a colour table consisting of 256 colour values. Colour Table Colour palette Red Green Blue 0 0 0 0 1 15 0 25 2 26 15 50 …………….. …………… ……………….. ………….. 127 150 165 80 255 255 255 255 The pixel will be stored as a colour value in the system. The graphic display system will covert the number by using correct value of red, blue and green. The hardware to cope with this demand needs such items as: additional memory, both VRAM and RAM additional hard disk space 5 E/kumar/multimedia system high processing speed to enable the number crunching involved in processing the data, which can range from video and audio back to word processing. A large resolution monitor or VDU with displaying capacity to enable it to display the digital data accurately. Roles of people who design multimedia. Job Role Skills needed 6 E/kumar/multimedia system 2. Examples of multimedia The area of multimedia has been growing rapidly over the past 10 years. As hardware and software have become more available for usage, even for everyday users, the needs of industry have continued to demand more and more processing speed and higher amounts of RAM to achieve the end goal. People involved in the multimedia industry have a variety of roles and require particular skills that enable the production of multimedia systems. Uses of Multimedia For each of the following areas, identify examples where multimedia could be used: Major area Example of multimedia usage. Education and training Leisure and entertainment Information Virtual reality and simulations A combination of these areas 7 E/kumar/multimedia system 3. Displaying multimedia systems The variety of hardware that is needed to display and create multimedia systems are: Screens – These can be CRT, LCD or touch screens Projection devices Speakers and sound systems CD-ROM Video Head-up displays and headsets – these are devices that are worn over the head to display information. Used in VR Common Types 1. The CRT or RGB monitors- the electron gun beams on the phosphorus coating on the screen which in turn lights up. A pattern of pixels or dots is used to build the complete image. Colour is produced by using three phosphorus dots per pixel. These dots are coloured and in most displays are red, blue and green. The varying intensity in which the dots glow determines the colour and shade being displayed. The two common types are raster display and vector display monitors. 2. The LCD consists of three layers of material. The first layer is the clear panel; the second is the grid containing the crystals while the third layer contains the light source. A current passing through the electrodes of the pixels causes the crystals either to block the light thereby forming the image. Colour is produced by placing filters over the light source. The LCD monitors have low resolutions and are slower to redraw images. 3. The Gas plasma displays use two glass panels. One panel contains vertical wires through which current is passed. The other panel has horizontal filaments. Pixels are placed at the intersection of these wires. When the current is passed through the horizontal and vertical filaments it glows at the intersections 8 E/kumar/multimedia system The LCD and gas plasma displays can be made very large but are costly. They are good for portable video games and small video telephones. They are also used for producing projection screens. Creating a multimedia system There are several methods that enable us to create a multimedia system using these display devices. The methods include the use of Type of software Examples Presentation software MS PowerPoint, HyperCard Authoring software Web browsers Application software Animation software HTML editors. 4. Other Information processes Processing Multimedia systems need to process data for presentation. This covers the aspects of how text, number, audio, image and video are integrated into the system. Since multimedia contains huge amount of data a lot of work has to be done before the image, sound or video can be displayed. The needs of the system are to compress data and decompress data as necessary in order to store and retrieve data effectively and therefore enable the presentation to run well. The need to use 9 E/kumar/multimedia system compression and decompression software becomes a necessary part of the multimedia system. Image Compression Image compression involves minimising the size in bytes of a file without degrading the quality of the image to an unacceptable level. The reduction in file size allows more information to be stored in a given amount of disk or memory space. It also reduces the time required for information to be sent over the Internet. 1. One method to reduce file sizes is to reduce the bit depth and the number of colours in an image. This process is called dithering. This will often reduce the quality especially in photographs. But if done with proper software quality can be maintained. E.g. Printing colour image on a non-colour printer. Or converting an image to a format that has less colour palette. 2. GIF images use data compression to reduce file storage size. The data in the image is compressed by removing duplicated data when the file is saved. When the image is reloaded the image is fully restored. This is termed as Loss less compression or non-lossy compression. 3. JPEG file format uses Lossy compression where chunks of data are removed permanently. Because of this we can specify what percentage data we want to lose. The image when reloaded will not be as perfect as the original. High level lossy compression produces very small files. 10 E/kumar/multimedia system 25% lossy compression Image at 100% zoom Image at 200% zoom File size = 1870 bytes File size= 10,153 bytes Video Compression Video compression is achieved by the use of a codec, a compression/ decompression algorithm. Codecs are drivers that compress and decompress data. By using codecs for compressing audio and video data into smaller packets that do not consume as much hard disk space or network bandwidth, multimedia applications can provide richer and fuller content. Two common video codecs: Indeo (created by Intel) MPEG-1, -2, and -3, created by the Moving Pictures Expert Group. Compression strategies can take advantage of four kinds of redundancy: Coding redundancy, which relies on the fact that not all data will occur with the same probability. Spatial redundancy, which occurs because pixels that are near each other are likely to be similar to each other. Temporal redundancy, which occurs because pixels in consecutive frames of a video are likely to be similar, for example a 'talking head'. Psycho visual redundancy, which occurs because the human visual system is better at detecting changes in luminance (brightness) than chrominance (colour). 11 E/kumar/multimedia system With digitised video speed is more important than the image quality. The best standard for video storage MPEG actually throws away chunks of data. STANDARD DESCRIPTION ADVANTAGES DISADVANTAGES M –JPEG standard Photographic Possible in very compression used quality images fast systems on every video frame MPEG-1 original MPEG Works on slow Low quality compression system systems and CD image designed to play drives Small screen videos directly playback from cd rom. drive MPEG-2 Standard for High Requires fast digital TV and DVD compression system playback format videos Better image quality Full screen playback MPEG-3 MPEG-4 Designed for video Works on slow Low image conferencing system quality Variety of network types and speeds 12 E/kumar/multimedia system Audio compression Multimedia audio files can be compressed to reduce their storage space and transmission time. LOSSY AUDIO COMPRESSION can be quickly described as the JPG of music: for a minor loss of quality we have a sound file which is many times smaller to the original and it can be easily broadcasted through the internet or transferred on portable media. MP3 MP3 is popular format for music on the web. Was developed to compress and store sound on CD ROM videos. Has a compression ratio of 1:10. It also removed digitised sounds that are beyond human hearing. WMA Windows Media Audio WMA filed can be streamed. They do not have to be downloaded to be played i.e.; Can be played as live music over the Internet. Compressed file size can be smaller than MP3. WMA is a lossy audio compression algorithm which works only as part of the Windows media player and not as a standard Windows codec (so that you may not convert WMA files to other formats). AAC Advanced Analogue Coding is the newest and the best of the Internet audio formats. Quality can be identical to MP3 but about half its size. It is based on MPEG-2 compression technology. It throws away sounds that we cannot hear. A powerful computer is needed for reliability. Different AAC players use different compression technologies and will not play each other’s files. RA Real Audio is a reliable format and provides acceptable quality in all given bitrates and all kinds of music. Version 8.5 has brought a few changes, some of which are not positive. The good news, Real Audio now provides CD quality bitrates. At phoneline speeds (20 and 34kbps) songs are clear and rich in high frequencies -- indeed very close to FM radio. At 90kbps and above, it is difficult to discern quality loss, though apparent is some overbrightness. Human hearing and voice Range is about 20 Hz to 20 kHz, most sensitive at 2 to 4 KHz. Dynamic range (quietest to loudest) is about 96 dB Normal voice range is about 500 Hz to 2 kHz o Low frequencies are vowels and bass o High frequencies are consonants Organising In order to organise a presentation from a multimedia system, we need to look at using a storyboard to show the flow of the screens. It generally includes text notes and important parts of the presentation. A storyboard can be in one of 3 main formats or a combination of all 3 together. The 3 main formats are: 13 E/kumar/multimedia system Linear Hierarchical Non-linear. Storing and Retrieving – How is image stored? All graphic data must be stored as bits, but the way the data is represented depends on whether the data is bitmap or vector data. Bitmap A paint program generates bit-mapped data. A bitmap is stored as a two-dimensional array representing the two-dimensional array of pixels found on the CRT. A simple monochrome image consists of two colours displayed by using the two states of a single bit (1 or 0). A 1 bit would cause a screen pixel to be lit and a 0 bit would cause a screen pixel to be unlit. 1. E.g. This file 010 101 010 11 2. On screen. 3. How it’s stored in memory 14 E/kumar/multimedia system Common bit map format is bmp while gif and jpeg are compressed bit map formats. Vector Line drawing programs generate vector data. These objects are stored in RAM as a descriptive list defined mathematically. The basic object shape can consist of primitives, such as lines, curves, circles or regular shapes. Each object is defined using a variety of properties (also characteristics or attributes) such as: object starting and ending positions (3-D coordinates) line direction or angle line length, colour, type (e.g. broken) and weight (thickness) closed-object fill colour light source position (creates shadows) Vector-refresh displays use of a display processing unit (DPU), which contains a microprocessor and a buffer (memory) that stores the display file. The display file holds a set of instructions about control points and electron beam intensity such as in the following example for drawing a rectangle: MOV 120, 40 (move to location at column 120 row 40) INT 10 (turns on the electron beam and sets the intensity to level 10) MOV 300, 40 (move to location at column 300 row 40 while drawing a line) MOV 300, 160 (move to location at column 300 row 160 while drawing a line) MOV 120, 160 (move to location at column 120 row 160 while drawing a line) MOV 120, 40 (move to location at column 120 row 40 while drawing a line) JMP 1 (causes the instructions from 1 to be repeated to refresh the image) Any vector graphics created using CAD programs have to be converted to bit maps, stored in the raster frame buffer and then displayed. Vector graphics CPU converts to Bit map Raster frame buffer Raster VDU Some common vector graphics format include cgm, eps and wmf 15 E/kumar/multimedia system Comparison of an image File Format (bit depth 24 and screen resolution of 1200X860) File format for an image File format Data file size Comments JPEG 481 KB 24 bit, high quality image for web GIF 541 8 bit colour common low quality web image BMP 2900KB 24 bit common paint format Audio and music storage Sound travels through the air in a wave form having a particular volume and pitch. Its analog data. To digitise it a process called sampling is used. Sampling has three important characters. 1. sampling rate- is the number of times a slice is taken in a second. The amplitude or volume is measured and converted to a number. Common sampling rates are 44.1 kHz and 22.5kHz(22050 slices per second) 2. Sampling size- is the number of bits per sample. Common sizes are 8 bit and 16bit. Cd quality sound require s 16 bit. 3. Mono or stereo sound. Mono is one channel while stereo is two channel sound. Calculation of audio file size Sample rate X sample size X time Sample rate = 44.1kHz 16 E/kumar/multimedia system Sample size = 16 bit Time = 3 minutes =44.1Khz x 16 x 3 =44100 x 16 x 180 bits If its stereo sound then multiply the answer by 2 File formats for Audio and Music files FILE FORMAT ADVANTAGES DISADVANTAGES MIDI Common format Music only .mid Small file size No voice or other sounds No browser plug ins needed MP3 Common format Some browsers need plug ins .mp3 High quality Very high compression Easy to create QuickTime Supports QuickTime Plug ins required as well as MIDI .mov Poor compression will create large files .qt RealAudio Live audio Plug ins required Speed can be varied Waveform Very common file Very large file sizes format .wav No plug in needed 17 E/kumar/multimedia system Video Processing and storage Video is an excellent way of making presentations. Video camera can be used to capture images in either analog or digital from. A video capture card is used to translate analog signals to digital. When displaying video we need to look at the speed at which the image will be shown. This is called the frame rate. Full screen video requires a lot of ram and a fast processor. Video images also require large storage areas. We have to consider the following Frame rate - normally 24 fps Time in seconds Frame resolution - horizontal X vertical pixels Bit depth E.g. A video consists of 90 minutes played at 24 fps. It has frame resolution of 1068 by 860 pixels and a bit depth of 32. Calculate the file size. Number of frames = frame rate X time in seconds = 24 x 90 x 60 =129, 600 frames Frame size = resolution X bit depth = 1068 x 860 x 32 bits = 1068 x 860 x 32 8 to get bytes and 1024 to get Kb = 1068 x 860 x 32 8 x 1024 = 3588 Kb File size of whole movie = 3588 x 129 6000 Kb = 465004800 Kb = 443.463 Gb. File formats for Videos and Animation files FILE FORMAT ADVANTAGES DISADVANTAGES 18 E/kumar/multimedia system Animated gif Common for web Limited to 256 animation colours .gif Easy to create No sound support Small file size Good for small images Flexible timing controls Macromedia Flash Small file size Browser plug ins required. .fla High quality Audio support Interactive features Flexible animation controls AVI Common format Large file size .avi Built into windows Limited features Supports audio MPEG Common video format Difficult to create .mpg Very high compression QuickTime Supports multiple Not suited to web formats applications .mov Supports Poor compression will .qt synchronised sounds create large files Browser plug ins required RealVideos Live video and Browser plug ins animation with audio required Quality depends on network speed 19 E/kumar/multimedia system Storage in CD ROM and DVD Audio CD, CD ROM and DVD use the same basic methods of storing and retrieving data. The surface of discs contains pits and lands. Each pit to land, and land to pit represents a 1 while the flat areas of both represents a sequence of 0s. This binary pattern is read by a laser. In DVDs the pits and lands are smaller and both sides of discs are used creating large storage space (17 Gigabytes) 5. Issues A multimedia system has a number of Social and Ethical issues that need to be addressed. Ethical issues relate to morals. Is it right or wrong to do something. Acknowledgment of the source of data within a multimedia system is necessary in order to satisfy copyright the data. Is it right to copy work someone has spent hours preparing. Copyright is important to the owner of the intellectual data that he/she be recognised therefore, obeying the copyright laws that cover all types of media. It is important that when you use data that is not your own it is acknowledged correctly and the author compensated. Accuracy of data should also be considered when viewing and downloading live video from the Internet. As a system user, the information obtained from any technology area needs to be used appropriately and accurately. Integrity of the data and information is vital not only for copyright purposes but also to enable the original to be used for educational purposes. Emerging technology on multimedia Advances in technology for such things as the World Wide Web, communication speed and capacity, CD ROM Speed and DVD have influenced the development of multimedia through the nature of these items. The WWW has changed the way we view data and has become increasingly more interactive. With the use of HTML and java script, web sites are becoming more interactive . The speed and capacity of communication have enabled the home user to interact with a web site through such items as home banking and Email. Although Email is 20 E/kumar/multimedia system essentially text based, other data items, such as audio and video, can be sent via Email, as attachments and therefore, the result can be interactive. CD ROM speed has improved, not only the speed of the CD itself but also the hardware drive it is read from. As speeds become higher and the use of CD burners becomes more common, their use within a multimedia system will become an everyday occurrence. The use of DVD’s has brought changes too. The extended usage of DVD players and DVD in homes has changed the way we view a video. Not only do we see the video as it was meant to be, but we can also interact with the DVD including playing games and screensavers. Streaming audio and video has allowed online broadcasting and Web TV. These can be played on the internet without the need for downloads. Not only do these influence the impact on multimedia systems we need to consider the use of other software, such as word processors and operating systems, which have become more orientated towards using the WWW. Review questions 1. What are the characteristics of multimedia systems? 2. Explain what each characteristic does in a multimedia system? 21 E/kumar/multimedia system 3. Describe what information technology is required in order for all these characteristics that can be utilized in a multimedia system? 4. Explain what information processes would be required to create a multimedia system? 5. Investigate the different file format for Audio Video Images Animation 6. What are the differences between the print media and multimedia? 7. Investigate the hardware needs to develop a multimedia system? 8. How has the World Wide Web, communication speed and capacity, CD ROM Speed and DVD influenced multimedia development? 9. Name each of the hardware devices for display purposes in a multimedia system. 10. Describe each type of screens used to display multimedia. 11. Explain how all 5 data structures are processed in a multimedia system? 12. Describe the 3 main formats of a storyboard. 13. What is a storyboard? What is its purpose? 14. Each of the data file formats given, explain how they operate in storing data. 15. Locate another 4 data file formats and explain how they operate in storing data. 16. Explain the methods of compression and decompression of data. 17. Find at least 2 software packages that compress and decompresses data. 18. Explain how data is collected in multimedia systems. 19. How is data changed from analog into digital form? 21. How is data captured and digitised in audio and video? 22 Describe the methods of digitising analog data. 23. Identify the Social and Ethical Issues in Multimedia Systems. References 22 E/kumar/multimedia system G.K. Powers Information Processes and Technology HSC Course G.Johnstone, M.Lowbridge, J. Smith Excel HSC Information Processes and Technology P.Ware,P.Cheleski, B.Chivers Information Processes and Technology HSC Course S.Alter Information Systems- a management perspective http://www.devx.com/projectcool/developer/gzone/basics/04-tech/lossy.html http://www.leadtools.com/video-codec_why.htm http://ekei.com/audio/ http://www.midi.org/ Additional Reading 23 E/kumar/multimedia system What is a codec? Codecs are drivers that compress and decompress data. By using codecs for compressing audio and video data into smaller packets that do not consume as much hard disk space or network bandwidth, multimedia applications can provide richer and fuller content. Why do I need a video codec? Video files can be very large if a good compression algorithm is not used. A live video can contain between 24 to 30 frames per second. A TV quality frame (640x480x24bits/pixel) consumes around 921,000 bytes. This equates to 27MB per second of just video data alone. How big is that? As an example a CD (650MB) would only store 24 seconds of video. Even if size did not matter, the storage devices (CD or hard disk) generally are not fast enough to handle this amount of data. This is valid for both reading or writing data. Compression algorithms were created to enable video to be saved on a computer. A compressor algorithm takes a original uncompressed image or /video and reduces its size. Because of the smaller size, the speed requirements for the storage devices are greatly reduced. To play back the compressed data, a decompression algorithm is used to decompress the data so it can be displayed on the screen. Video codecs were created to allow existing applications (Media Player® and Ulead Media Studio®) to communicate with the compression algorithms. Also, video files created with one application can be read and played back using a different application provided that the appropriate decoder (codec) is installed. Additionally, because codecs are separate piece of software from the parent application, codecs can be enhanced and upgraded without having to upgrade the parent application and having to learn a new user interface. MJPEG is a standard single-frame compression algorithm. Each frame is compressed using JPEG compression. Being a standard type of encoding, MJPEG files created on a computer with a software codec or hardware capture board can be played on another computer using another MJPEG codec or another hardware capture board 24 E/kumar/multimedia system What is MIDI The Musical Instrument Digital Interface (MIDI) enables people to use multimedia computers and electronic musical instruments to create, enjoy and learn about music. There are actually three components to MIDI Protocol which is the communications language Connector hardware interface Standard MIDI Files a distribution format called. Protocol The MIDI protocol is an entire music description language in binary form. Each word describing an action of musical performance is assigned a specific binary code. MIDI was designed for keyboards, so many of the actions are percussion oriented. To sound a note in MIDI language you send a "Note On" message, and then assign that note a "velocity", which determines how loud it plays. Other MIDI messages include selecting which instrument to play, mixing and panning sounds, and controlling various aspects of electronic musical instruments. Standard MIDI Files When MIDI messages are stored on disks, they are commonly saved in the Standard MIDI file format, which is slightly different from native MIDI protocol, because the events are also time-stamped for playback in the proper sequence. Just about every personal computer is now equipped to play Standard MIDI files. MIDI files do not need to capture and store actual sounds. Instead, the MIDI file can be just a list of events which describe the specific steps that a soundcard or other playback device must take to generate certain sounds. This way, MIDI files are very much smaller than digital audio files, and the events are also editable, allowing the music to be rearranged, edited, even composed interactively, if desired. Connector According to the MIDI 1.0 Specification, the only approved MIDI connector is a 5- pin DIN connector. Meanwhile, since many personal computers do not have space for a 5-pin DIN connector, many manufacturers have decided to use either a serial port or a joystick port to connect to MIDI instruments. A few MIDI instruments are actually equipped with an 8-pin "mini DIN" serial port, which makes it possible to connect those devices directly to some computers. But the only way to connect a 5-pin DIN equipped MIDI device to a computer's joystick port is via a special adapter cable, which usually must be purchased separately. 25 E/kumar/multimedia system A simple MIDI system Computer based MIDI system Expanded MIDI sytem 26 E/kumar/multimedia system 26 E/kumar/multimedia system