1. Theoretical Foundations of Multimedia Chapter 3 Theoretical Foundations of Multimedia Dr. Robert S. Tannenbaum Director, Academic Computing Services University of Kentucky rst@pop.uky.edu

2. Theoretical Foundations of Multimedia Chapter 3 Hardware that Enables Multimedia Input and Output Devices Input and Output Devices Virtual Reality Devices Virtual Reality Devices Modems and Network Interfaces Modems and Network Interfaces

3. Theoretical Foundations of Multimedia Chapter 3 Input and Output Devices Monitors Monitors Speakers and MIDI interfaces Speakers and MIDI interfaces VR helmets and immersive displays VR helmets and immersive displays Keyboards and OCR devices Keyboards and OCR devices Digital cameras, scanners, & CD-ROMs Digital cameras, scanners, & CD-ROMs MIDI keyboards and microphones MIDI keyboards and microphones Video cameras and frame grabbers Video cameras and frame grabbers Mice, track balls, joysticks, and VR gloves and wands Mice, track balls, joysticks, and VR gloves and wands Output Input

4. Theoretical Foundations of Multimedia Chapter 3 Monitors A simplified cathode ray tube (CRT)

5. Theoretical Foundations of Multimedia Chapter 3 Monitors Pixel — a picture element; a dot of color on the screen Pixel — a picture element; a dot of color on the screen Three different phosphors at each pixel to create the color Three different phosphors at each pixel to create the color RGB ( Red, Green, Blue) RGB ( Red, Green, Blue) CYM (Cyan, Yellow, Magenta) CYM (Cyan, Yellow, Magenta)

6. Theoretical Foundations of Multimedia Chapter 3 Monitors Raster Scanning

7. Theoretical Foundations of Multimedia Chapter 3 Monitors Refresh rate — the frequency at which the phosphors are excited Refresh rate — the frequency at which the phosphors are excited Normally the refresh rate is givenin Hertz Normally the refresh rate is givenin Hertz For flicker-free images 75 Hz or faster is desirable For flicker-free images 75 Hz or faster is desirable The refresh rate for a projector needs to be coordinated with the monitor The refresh rate for a projector needs to be coordinated with the monitor

8. Theoretical Foundations of Multimedia Chapter 3 Monitors The digitized image to be displayed must be stored in a buffer The digitized image to be displayed must be stored in a buffer The stored image is said to be “bit-mapped,” because, for monochrome images, the map used just one bit per pixel The stored image is said to be “bit-mapped,” because, for monochrome images, the map used just one bit per pixel Multimedia monitors use 24 bits per pixel (8 for each color); can define >16 million colors Multimedia monitors use 24 bits per pixel (8 for each color); can define >16 million colors

9. Theoretical Foundations of Multimedia Chapter 3 A Good Multimedia Monitor Large enough for comfortable viewing, probably 15” or greater Large enough for comfortable viewing, probably 15” or greater Pixel size of no more than 0.28mm Pixel size of no more than 0.28mm Refresh rate of at least 75 Hz Refresh rate of at least 75 Hz Capable of displaying 24-bit color Capable of displaying 24-bit color Designed for the CPU and operating system Designed for the CPU and operating system Ergonomically comfortable and attractive Ergonomically comfortable and attractive

10. Theoretical Foundations of Multimedia Chapter 3 Speakers and MIDI Interfaces Speakers and MIDI Interfaces Storage of digitized sound files Storage of digitized sound files Reproduction via digital-to-analog conversion sent to a loudspeaker Reproduction via digital-to-analog conversion sent to a loudspeaker Built-in speakers often do not have sufficient fidelity Built-in speakers often do not have sufficient fidelity Low-powered (3- to 5-watt) external speakers or head- phones will serve a single user and provide excellent fidelity Low-powered (3- to 5-watt) external speakers or head- phones will serve a single user and provide excellent fidelity

11. Theoretical Foundations of Multimedia Chapter 3 Storage of synthesizer command files Storage of synthesizer command files Create the sounds by sending thecommands to a synthesizer Create the sounds by sending thecommands to a synthesizer Musical Instrument Digital Interface (MIDI) standard (1982) Musical Instrument Digital Interface (MIDI) standard (1982) MIDI includes both a hardware and a message standard MIDI includes both a hardware and a message standard Speakers and MIDI Interfaces Speakers and MIDI Interfaces

12. Theoretical Foundations of Multimedia Chapter 3 Speakers and MIDI Interfaces MIDI hardware standard defines cables, connectors, circuits, andelectrical signals MIDI hardware standard defines cables, connectors, circuits, andelectrical signals MIDI message standard defines a MIDI message standard defines a  Device number for multiple device systems  Control segment that gives an instrument-specific command  Data segment containing the information needed by that instrument for that command

13. Theoretical Foundations of Multimedia Chapter 3 Alphanumeric Keyboards For entering commands, text, and data For entering commands, text, and data Each key is a switch that closes when it is depressed, sending a code to the CPU Each key is a switch that closes when it is depressed, sending a code to the CPU The arrangement of the keys may vary The arrangement of the keys may vary The most common is QWERTY The most common is QWERTY Another arrangement is Dvorak Another arrangement is Dvorak

14. Theoretical Foundations of Multimedia Chapter 3 Choosing a Keyboard Does it include all of the needed characters, including command keys? Does it include all of the needed characters, including command keys? Is it ergonomically comfortable and safe, preventing repetitive stress syndrome? Is it ergonomically comfortable and safe, preventing repetitive stress syndrome?

15. Theoretical Foundations of Multimedia Chapter 3 Optical Character Recognition (OCR) Hardware — scans the text image Hardware — scans the text image Software — systematically checksthe entire image for patterns of light and dark that it recognizes as alphabetic, numeric, or punctuation characters Software — systematically checksthe entire image for patterns of light and dark that it recognizes as alphabetic, numeric, or punctuation characters OCR software entails pattern recognition, a sophisticated logic problem OCR software entails pattern recognition, a sophisticated logic problem

16. Theoretical Foundations of Multimedia Chapter 3 E e E E e e E E E e e E E E e e E e e It is relatively easy for a human to recognize each of these characters as the letter “e.” For the pattern recognition logic in OCR software, this is very difficult. Optical Character Recognition (OCR)

17. Theoretical Foundations of Multimedia Chapter 3 Digital Cameras and Scanners Real Image — Real Image — a portion of what is physically present in nature Digital Image — Digital Image — a representation of a real image in which individual points are encoded to represent the wavelength and intensity of light at that point Still Image — Still Image — a single snapshot of an instant; may be real or digital Motion Image — Motion Image — a sequence of images that, when viewed consecutively at the appropriate rate, gives the impression of continuous motion; may be digital or analog

18. Theoretical Foundations of Multimedia Chapter 3 Scanners Schematic Drawing of a Scanner

19. Theoretical Foundations of Multimedia Chapter 3 Digital Cameras Schematic Drawing of a Digital Camera

20. Theoretical Foundations of Multimedia Chapter 3 Digital Cameras and Scanners Quality of the optics and the scanning mechanism, which determines focus Quality of the optics and the scanning mechanism, which determines focus Precision of the photosensitive cells, which determines the accuracy of the encoding of intensity and wavelength data Resolution of the instrument in dots per inch, which determines graininess Amount of storage available, which determines the total size of an image that can be digitized Image quality depends on the:

21. Theoretical Foundations of Multimedia Chapter 3 Inputting Images Memory required to store a 5” x 7” snapshot Dots/inch resolution of snapshot image 100 300 600 1200 Bytes required for storage 1.05 Mb 9.45 Mb 37.8 Mb 151.2 Mb Assuming no compression, 24 bits per pixel

22. Theoretical Foundations of Multimedia Chapter 3 Video Cameras and Frame Grabbers Video cameras are similar to digital cameras Video cameras are similar to digital cameras Except that a video camera takes image after image continuously Except that a video camera takes image after image continuously The output from many video cameras is analog and requires digitizing circuitry to make the image usable in a computer The output from many video cameras is analog and requires digitizing circuitry to make the image usable in a computer Digital camcorders are now available Digital camcorders are now available Frame grabber software allows the capture ofa single still image from the video stream Frame grabber software allows the capture ofa single still image from the video stream Frame grabbed images are of rather low resolution, however, <80-90 dots/inch Frame grabbed images are of rather low resolution, however, <80-90 dots/inch

23. Theoretical Foundations of Multimedia Chapter 3 Microphones and MIDI Keyboards For input of sound For input of sound Microphones capture sound waves from the air as an analog signal Microphones capture sound waves from the air as an analog signal The analog signal must be digitized to be stored and then replayed by the computer The analog signal must be digitized to be stored and then replayed by the computer Digitizing at <10,000 Hz is adequate for speech; 20,000-40,000 Hz is needed for music Digitizing at <10,000 Hz is adequate for speech; 20,000-40,000 Hz is needed for music MIDI keyboards usually look like piano key- boards with extra switches and controls MIDI keyboards usually look like piano key- boards with extra switches and controls MIDI keyboards encode and transmit musical information according to the MIDI standard MIDI keyboards encode and transmit musical information according to the MIDI standard