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Transcript of Theoretical Foundations of Multimedia Chapter 3 Hardware that Enables Multimedia n Input and Output...
Theoretical Foundations of Multimedia Chapter 3
Hardware that Enables Hardware that Enables MultimediaMultimedia
Input and Output DevicesInput and Output Devices
Virtual Reality DevicesVirtual Reality Devices
Modems and Network InterfacesModems and Network Interfaces
Theoretical Foundations of Multimedia Chapter 3
Input and Output DevicesInput and Output Devices
MonitorsMonitors Speakers and MIDI interfacesSpeakers and MIDI interfaces VR helmets and immersive displaysVR helmets and immersive displays Keyboards and OCR devicesKeyboards and OCR devices Digital cameras, scanners, & CD-ROMsDigital cameras, scanners, & CD-ROMs MIDI keyboards and microphonesMIDI keyboards and microphones Video cameras and frame grabbersVideo cameras and frame grabbers Mice, track balls, joysticks, and VRMice, track balls, joysticks, and VR gloves and gloves and
wandswands
OutputOutput
InputInput
Theoretical Foundations of Multimedia Chapter 3
MonitorsMonitors
A simplified cathode ray tube (CRT)A simplified cathode ray tube (CRT)
Theoretical Foundations of Multimedia Chapter 3
MonitorsMonitors
Pixel — a picture element; a dot Pixel — a picture element; a dot of color on the screenof color on the screen
Three different phosphors at Three different phosphors at each pixel to create the coloreach pixel to create the color
RGB (RGB (Red, Red, green, green, blueblue)) CYM (CYM (CyanCyan, , yellowyellow, , magentamagenta))
Theoretical Foundations of Multimedia Chapter 3
MonitorsMonitors
Raster ScanningRaster Scanning
Theoretical Foundations of Multimedia Chapter 3
MonitorsMonitors
Refresh rate — the frequency atRefresh rate — the frequency at which which the phosphors are excitedthe phosphors are excited
Normally the refresh rate is givenNormally the refresh rate is given in Hertzin Hertz For flicker-free images 75 Hz orFor flicker-free images 75 Hz or faster is faster is
desirabledesirable The refresh rate for a projector needs The refresh rate for a projector needs
to be coordinated with the monitorto be coordinated with the monitor
Theoretical Foundations of Multimedia Chapter 3
MonitorsMonitors
The digitized image to be displayed The digitized image to be displayed must be must be stored in a bufferstored in a buffer
The stored image is said to beThe stored image is said to be “bit-“bit-mapped,” because, for mapped,” because, for monochrome monochrome images, the map images, the map used just one bit per used just one bit per pixelpixel
Multimedia monitors use 24 bitsMultimedia monitors use 24 bits per per pixel (8 for each color); canpixel (8 for each color); can define define >16 million colors>16 million colors
Theoretical Foundations of Multimedia Chapter 3
A Good Multimedia MonitorA Good Multimedia Monitor
Large enough for comfortableLarge enough for comfortable viewing, viewing, probably 15” or greaterprobably 15” or greater
Pixel size of no more than 0.28mmPixel size of no more than 0.28mm Refresh rate of at least 75 HzRefresh rate of at least 75 Hz Capable of displaying 24-bit colorCapable of displaying 24-bit color Designed for the CPU and operatingDesigned for the CPU and operating systemsystem Ergonomically comfortable andErgonomically comfortable and
attractiveattractive
Theoretical Foundations of Multimedia Chapter 3
Speakers and Speakers and MIDI InterfacesMIDI Interfaces
Storage of digitized sound filesStorage of digitized sound files Reproduction via digital-to-analog Reproduction via digital-to-analog
conversion sent to a loudspeakerconversion sent to a loudspeaker Built-in speakers often do not haveBuilt-in speakers often do not have sufficient sufficient
fidelityfidelity Low-powered (3- to 5-watt) externalLow-powered (3- to 5-watt) external
speakers or head-phones will serve a speakers or head-phones will serve a single single user and provide excellent fidelityuser and provide excellent fidelity
Theoretical Foundations of Multimedia Chapter 3
Storage of synthesizer command files Storage of synthesizer command files Create the sounds by sending theCreate the sounds by sending the
commands to a synthesizercommands to a synthesizer Musical Instrument Digital InterfaceMusical Instrument Digital Interface
(MIDI) standard (1982)(MIDI) standard (1982) MIDI includes both a hardware and a message MIDI includes both a hardware and a message
standardstandard
Speakers and Speakers and MIDI InterfacesMIDI Interfaces
Theoretical Foundations of Multimedia Chapter 3
Speakers and MIDI InterfacesSpeakers and MIDI Interfaces
MIDI hardware standard defines MIDI hardware standard defines cables, connectors, circuits, cables, connectors, circuits, andandelectrical signalselectrical signals
MIDI message standard defines aMIDI 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
Theoretical Foundations of Multimedia Chapter 3
Alphanumeric KeyboardsAlphanumeric Keyboards
For entering commands, text, For entering commands, text, and dataand data Each key is a switch that closesEach key is a switch that closes when it is when it is
depressed, sending adepressed, sending a code to the CPUcode to the CPU The arrangement of the keys mayThe arrangement of the keys may
varyvary The most common is QWERTYThe most common is QWERTY Another arrangement is DvorakAnother arrangement is Dvorak
Theoretical Foundations of Multimedia Chapter 3
Choosing a KeyboardChoosing a Keyboard
Does it include Does it include allall of the needed of the neededcharacters, including command characters, including command keys?keys?
Is it ergonomically comfortableIs it ergonomically comfortableand safe, preventing repetitive and safe, preventing repetitive stress stress syndrome?syndrome?
Theoretical Foundations of Multimedia Chapter 3
Optical Character Recognition Optical Character Recognition (OCR)(OCR)
Hardware — scans the text imageHardware — scans the text image Software — systematically checksSoftware — systematically checks the the
entire image for patterns ofentire image for patterns of light and light and dark that it recognizesdark that it recognizes as alphabetic, as alphabetic, numeric, or punc-numeric, or punc- tuation characterstuation characters
OCR software entails pattern OCR software entails pattern recognition, a sophisticated recognition, a sophisticated logic logic problemproblem
Theoretical Foundations of Multimedia Chapter 3
E e E E e e E E e Ee 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 Optical Character Recognition (OCR)(OCR)
Theoretical Foundations of Multimedia Chapter 3
Digital Cameras and ScannersDigital 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 appro- priate rate, gives the impression of con- tinuous motion; may be digital or analog
Theoretical Foundations of Multimedia Chapter 3
ScannersScanners
Schematic Drawing of a ScannerSchematic Drawing of a Scanner
Theoretical Foundations of Multimedia Chapter 3
Digital CamerasDigital Cameras
Schematic Drawing of a Digital CameraSchematic Drawing of a Digital Camera
Theoretical Foundations of Multimedia Chapter 3
Digital Cameras and ScannersDigital Cameras and Scanners
Quality of the optics and the scanning Quality of the optics and the scanning mechanism, which determines focusmechanism, which determines focus
Precision of the photosensitive cells, whichPrecision of the photosensitive cells, whichdetermines the accuracy of the encodingdetermines the accuracy of the encoding of of intensity and wavelength dataintensity and wavelength data
Resolution of the instrument in dots perResolution of the instrument in dots per inch, inch, which determines graininesswhich determines graininess
Amount of storage available, which deter-Amount of storage available, which deter-minesmines the total size of an image that can the total size of an image that can be be digitizeddigitized
Image quality depends on the:Image quality depends on the:
Theoretical Foundations of Multimedia Chapter 3
Inputting ImagesInputting Images
Memory required to store a 5” x 7” snapshotMemory required to store a 5” x 7” snapshot
Dots/inch resolutionof snapshot image
100300600
1200
Bytes requiredfor storage
1.05 Mb9.45 Mb37.8 Mb
151.2 Mb
Assuming no compression, 24 bits per pixel
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Theoretical Foundations of Multimedia Chapter 3
Video Cameras and Video Cameras and Frame Frame GrabbersGrabbers
Video cameras are similar to digital camerasVideo cameras are similar to digital cameras Except that a video camera takes image Except that a video camera takes image after image after image
continuouslycontinuously The output from many video cameras isThe output from many video cameras is
analog and requires digitizing circuitryanalog and requires digitizing circuitry to make the to make the image usable in a computerimage usable in a computer
Digital camcorders are now available Digital camcorders are now available Frame grabber software allows the capture ofFrame grabber software allows the capture of a a
single still image from the video streamsingle still image from the video stream Frame grabbed images are of rather lowFrame grabbed images are of rather low
resolution, however, <80-90 dots/inchresolution, however, <80-90 dots/inch
Theoretical Foundations of Multimedia Chapter 3
Microphones and Microphones and MIDI KeyboardsMIDI Keyboards
For input of soundFor input of sound Microphones capture sound waves from theMicrophones capture sound waves from the air air
as an analog signalas an analog signal The analog signal must be digitized to be The analog signal must be digitized to be stored and stored and
then replayed by the computerthen replayed by the computer Digitizing at <10,000 Hz is adequate forDigitizing at <10,000 Hz is adequate for
speech; 20,000 Hz is needed for musicspeech; 20,000 Hz is needed for music MIDI keyboards usually look like piano key-MIDI keyboards usually look like piano key-
boards with extra switches and controlsboards with extra switches and controls MIDI keyboards encode and transmit musical MIDI keyboards encode and transmit musical
informationinformation according to the MIDI standard according to the MIDI standard
Theoretical Foundations of Multimedia Chapter 3
Inputting Positional Inputting Positional InformationInformation
MiceMice TrackballsTrackballs Track padsTrack pads JoysticksJoysticks Drawing tabletsDrawing tablets
Theoretical Foundations of Multimedia Chapter 3
Inputting Positional Inputting Positional InformationInformation
Specifying a point on a surface Specifying a point on a surface requires two dimensions, asrequires two dimensions, aswith latitude and longitudewith latitude and longitude
A third dimension could be added, A third dimension could be added, as with as with altitudealtitude
For multimedia, what is commonly For multimedia, what is commonly needed needed is position on the monitor is position on the monitor in terms of left-in terms of left-right (X) and up-right (X) and up- down (Y) distancesdown (Y) distances
Theoretical Foundations of Multimedia Chapter 3
Inputting Positional Inputting Positional InformationInformation
X and Y coordinates are obtainedX and Y coordinates are obtainedrelative to a fixed point, usuallyrelative to a fixed point, usually one one corner of the screencorner of the screen
The coordinates are entered inThe coordinates are entered in analog analog form as output from roll-form as output from roll- ing wheels ing wheels inside a device such inside a device such as a mouseas a mouse
The analog values are digitized toThe analog values are digitized tospecify the X and Y coordinatesspecify the X and Y coordinates
Theoretical Foundations of Multimedia Chapter 3
The Mechanism of a MouseThe Mechanism of a Mouse
Theoretical Foundations of Multimedia Chapter 3
Using a Drawing TabletUsing a Drawing Tablet
Theoretical Foundations of Multimedia Chapter 3
Created in part using a drawing tabletCreated in part using a drawing tablet © Janet Anderson
Collage by Janet AndersonCollage by Janet AndersonQuickTime™ and a
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QuickTime™ and aPhoto - JPEG decompressor
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QuickTime™ and aPhoto - JPEG decompressor
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Photo - JPEG decompressorare needed to see this picture.
QuickTime™ and aPhoto - JPEG decompressor
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QuickTime™ and aPhoto - JPEG decompressor
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Photo - JPEG decompressorare needed to see this picture.
QuickTime™ and aPhoto - JPEG decompressor
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Photo - JPEG decompressorare needed to see this picture.QuickTime™ and a
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Theoretical Foundations of Multimedia Chapter 3
CD-ROMs, DVDs, and CD-ROMs, DVDs, and Video DisksVideo Disks
Media for external storage and Media for external storage and transport of datatransport of data Compact disk—read-only memory Rewritable compact disk (CD-RW) DVD Video disk (laser disk); analog
format
Theoretical Foundations of Multimedia Chapter 3
CD-ROMsCD-ROMs
Digital formatDigital format Write once, read many timesWrite once, read many times A rewritable version (CD-RW) is available,A rewritable version (CD-RW) is available, but but
not in common usenot in common use Information is “written” by burning tiny Information is “written” by burning tiny
holes in the disk surface with a laserholes in the disk surface with a laser The hole pattern is read by a laser and inter-The hole pattern is read by a laser and inter-
preted as the bits comprising the datapreted as the bits comprising the data Can store 600-700 megabytes of data; aboutCan store 600-700 megabytes of data; about
300,000 pages of double-spaced text, or300,000 pages of double-spaced text, or more than more than an hour of high fidelity soundan hour of high fidelity sound
Theoretical Foundations of Multimedia Chapter 3Creating Creating
Multimedia Multimedia CD-CD-
ROMsROMs Requires a hard disk large enough to storeRequires a hard disk large enough to store
~650 megabytes of data to be written~650 megabytes of data to be written to the to the CDCD
Requires a CD-ROM recorder that writes theRequires a CD-ROM recorder that writes thedata to the blank CD using a laserdata to the blank CD using a laser
The developer creates the multimedia mater-The developer creates the multimedia mater-ial, stores it on the hard disk, and then ial, stores it on the hard disk, and then tests it as tests it as completely as possiblecompletely as possible
When the material is in final form, it isWhen the material is in final form, it iswritten to the blank CD as if it werewritten to the blank CD as if it werebeing copied from one disk to anotherbeing copied from one disk to another
Theoretical Foundations of Multimedia Chapter 3
Video Disks orVideo Disks orLaser DisksLaser Disks
Much larger than a CD-ROM; ~12” in diameterMuch larger than a CD-ROM; ~12” in diameter Hold ~54,000 video frames per sideHold ~54,000 video frames per side Hold ~30 minutes of video per sideHold ~30 minutes of video per side Read-onlyRead-only Analog formatAnalog format Requires a conversion board to be used with a Requires a conversion board to be used with a
computercomputer Excellent for large-scale, video-based multimedia Excellent for large-scale, video-based multimedia
projectsprojects
Theoretical Foundations of Multimedia Chapter 3
Virtual Reality DevicesVirtual Reality Devices Non interactive
Slow image update rate
Simple image
Nonengaging content and presentation
No sound
Basic Screen display
Low resolution image
Monoscopic image
Small field of view
No head tracking
No body motion sensing
No tactile feedback
Highly interactive
Fast image update rate
Highly complex image
Highly engaging content and presentation
Three-dimensional sound
Head-mounted display
High resolution image
Stereoscopic image
Full field of view
Full head tracking
Full body motion sensing
Full tactile feedback
Factors affecting the degree of immersion in virtual reality
Theoretical Foundations of Multimedia Chapter 3
NCSA’s CAVENCSA’s CAVE
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Theoretical Foundations of Multimedia Chapter 3
NCSA’s CAVENCSA’s CAVE
• Virtual Reality Room with stereo glasses and magnetic head/hand tracking
• Fully immersive using three of four walls to display the graphics
• Uses an SGI Power Onyx with Reality Engine 2 software
Theoretical Foundations of Multimedia Chapter 3
NCSA’s ImmersaDeskNCSA’s ImmersaDesk
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Miniature version of NCSA’s CAVE
Theoretical Foundations of Multimedia Chapter 3
NCSA’s ImmersaDeskNCSA’s ImmersaDesk
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Drafting-table format virtual prototyping device
Theoretical Foundations of Multimedia Chapter 3
NCSA’s ImmersaDeskNCSA’s ImmersaDesk
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Uses CAVE’s stereo glasses and magnetic head/hand tracking
Theoretical Foundations of Multimedia Chapter 3
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NCSA’s ImmersaDeskNCSA’s ImmersaDesk
Semi-immersive, fills the user’s field of vision
Theoretical Foundations of Multimedia Chapter 3
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NCSA’s ImmersaDeskNCSA’s ImmersaDesk
Uses an identical SGI Power Onyx with the same Reality
Engine 2 software as the CAVE
Theoretical Foundations of Multimedia Chapter 3
VR Head-Mounted DisplayVR Head-Mounted Display
Theoretical Foundations of Multimedia Chapter 3
VR Head-Mounted DisplayVR Head-Mounted DisplayLimitations:Limitations: Liquid Crystal Displays (LCDs)Liquid Crystal Displays (LCDs)
pixels not as small as a CRT pixels not as bright as a CRT cannot change as quickly as a CRT short focal distance makes precision, high
resolution, and rapid response even more essential Muscle receptor feedback confusionMuscle receptor feedback confusion
light rays indicate “distant” muscles indicate “very close”
Theoretical Foundations of Multimedia Chapter 3
VR Head-Mounted DisplayVR Head-Mounted Display Parallax — the apparent change in position of a Parallax — the apparent change in position of a
stationary object when viewed from slightly stationary object when viewed from slightly different positionsdifferent positions
A person’s eyes each see a slightly different view of A person’s eyes each see a slightly different view of an objectan object
As the brain receives these two images, it interprets As the brain receives these two images, it interprets the the distance to the object in terms of the the the distance to the object in terms of the difference in position of the object in the two imagesdifference in position of the object in the two images
Parallax can be used to fool the brain into “seeing” Parallax can be used to fool the brain into “seeing” images as being at various distancesimages as being at various distances
Theoretical Foundations of Multimedia Chapter 3
DemonstratingDemonstratingParallaxParallax
Pencil
Looking at a pencil aligned What is seen using with the corner of a room both eyes
What is seen with What is seen withright eye covered left eye covered
Theoretical Foundations of Multimedia Chapter 3
StereoscopeStereoscope
Courtesy of Special Collections, M. I. King Library, University of Kentucky
Theoretical Foundations of Multimedia Chapter 3
Parallax Problems withParallax Problems withVR Head-Mounted DisplaysVR Head-Mounted Displays
Images may not be perfectly realistic, Images may not be perfectly realistic, especially especially with motion imageswith motion images
When the observer’s head moves and the eyes are When the observer’s head moves and the eyes are refocused, muscle receptor feedback data does not refocused, muscle receptor feedback data does not correlate with visual cuescorrelate with visual cues
The perspective is always that of the camera, never the The perspective is always that of the camera, never the viewer’s eyesviewer’s eyes
A viewer motion feedback mechanism is needed to A viewer motion feedback mechanism is needed to change the perspectivechange the perspective
This all contributes to “cybersicknessThis all contributes to “cybersickness””
Theoretical Foundations of Multimedia Chapter 3
VR Aural OutputVR Aural Output
Refer to the discussion in chapter 2 regarding the Refer to the discussion in chapter 2 regarding the perception of soundperception of sound
Two key factors Two key factors Localization Identification
The brain interprets differences in the signals it receives The brain interprets differences in the signals it receives from the two ears in a manner analogous to binocular from the two ears in a manner analogous to binocular visionvision
For multimedia sound to be completely realistic, it requires For multimedia sound to be completely realistic, it requires head-position sensing feedback and enormous head-position sensing feedback and enormous computational power — not practical for most multimediacomputational power — not practical for most multimedia
Theoretical Foundations of Multimedia Chapter 3
VR Input DevicesVR Input Devices
The terminology of three-dimensional motion
y
x
z
Origin
Roll
Yaw
Pitch
Theoretical Foundations of Multimedia Chapter 3
VR Position SensingVR Position Sensing
A point in space is defined in terms of A point in space is defined in terms of distance along three mutually perpen-distance along three mutually perpen-dicular axes, usually termed X, Y, and Zdicular axes, usually termed X, Y, and Z
Motion is defined in terms of changes in Motion is defined in terms of changes in position, which requires six parametersposition, which requires six parameters
Devices that can sense and record Devices that can sense and record motion are motion are termed six-degrees-of-freedom (6-DOF) devicestermed six-degrees-of-freedom (6-DOF) devices
Theoretical Foundations of Multimedia Chapter 3
VR Position SensingVR Position Sensing Sensor output from a 6-DOF device can beSensor output from a 6-DOF device can be
continuous polled, or sent only upon request
Parameters to consider in evaluating a Parameters to consider in evaluating a tracking device:tracking device: Lag or Latency — the delay between the actual time of the
motion and when it is available as input data; should be <50 mSec
Update rate — Rate at which measurements are made; should be as fast as possible
Precision or accuracy of the measurements Range over which the sensors operate Rejection of interference
Theoretical Foundations of Multimedia Chapter 3
VR Voice InputVR Voice Input Speech RecognitionSpeech Recognition Complications due to variations inComplications due to variations in
Pitch Timbre Volume Speed of Delivery Inflection Accent
Natural language processingNatural language processing
Theoretical Foundations of Multimedia Chapter 3
Natural Language ProcessingNatural Language Processing
Put out the light.Put out the light. Turn off the light.Turn off the light. Close the light, please.Close the light, please. The light, turn it off.The light, turn it off. Please, shut the light.Please, shut the light. Kill the lights.Kill the lights.
Theoretical Foundations of Multimedia Chapter 3
Natural Language ProcessingNatural Language Processing
Only the son praised his sister.Only the son praised his sister. (The rest of the family did not.)
The only son praised his sister.The only son praised his sister. (There was just one son.)
The son only praised his sister.The son only praised his sister. (He never found fault with her.)
The son praised only his sister.The son praised only his sister. (But never anyone else.)
The son praised his only sister.The son praised his only sister. (He had just one sister.)
The son praised his sister only.The son praised his sister only. (In this instance, he praised no one but her.)
Theoretical Foundations of Multimedia Chapter 3
Modems andModems andNetwork InterfacesNetwork Interfaces
Serial and ParallelSerial and Parallel Serial — the bits arrive sequentially Parallel — the bits arrive simultaneously
Character encodingCharacter encoding ASCII — American standard code for information
interchange EBCDIC — Extended binary-coded decimal
interchange code Unicode
Theoretical Foundations of Multimedia Chapter 3
ASCII and UnicodeASCII and Unicode
ASCII is limited because it is only a 7- ASCII is limited because it is only a 7- or 8- or 8-bit code; even using “escape sequences” only a bit code; even using “escape sequences” only a small number of characters can be encodedsmall number of characters can be encoded
Unicode is a 16-bit code that can Unicode is a 16-bit code that can encode encode many primary scripts plus many primary scripts plus special special character sets known as character sets known as secondary scriptssecondary scripts
Theoretical Foundations of Multimedia Chapter 3
Unicode ScriptsUnicode ScriptsPrimary scripts:Primary scripts:
Arabic Georgian Hebrew MalayalamArmenian Greek Hiragana OriyaBengali Gujarati Kannada PhoneticBopomofo Gurmkhi Katakana TamilCyrillic Han Latin TeluguDevanagari Hangul Lao Thai
Secondary scripts:Secondary scripts:
Numbers General diacriticsGeneral symbols Miscellaneous symbolsGeneral Punctuation Technical symbolsDingbats Mathematical symbolsPresentation formsArrows, blocks, box drawing forms, and geometric shapes
Theoretical Foundations of Multimedia Chapter 3
Modems andModems andNetwork InterfacesNetwork Interfaces
Start bitsStart bits Opposite bit from the system idle state Necessary to alert the receiver to the beginning of a new
character
Stop bitsStop bits Provide a short delay at the end of each character to
give the receiver enough time to convert from serial to parallel
Error-checking codesError-checking codes Parity bits, CRC bits, etc. Discussed in chapter 6
Theoretical Foundations of Multimedia Chapter 3
Modems andModems andNetwork InterfacesNetwork Interfaces
Transmission rateTransmission rate Internal transfer rates are much faster than data rates
over networks The interface needs to “interrupt” the
computer when it has new data, not keep it from doing other processing while data is being received
Transmission formTransmission form Connection via a telephone line requires a modem
(MOdulator-DEModulator) to translate the internal data transfer format into an audio signal, and vice-versa
Theoretical Foundations of Multimedia Chapter 3
Modems andModems andNetwork InterfacesNetwork Interfaces
Use of modems and telephone lines Use of modems and telephone lines for connectivityfor connectivity