Digitization of Audio.ppt

  • View
    4.434

  • Download
    0

Embed Size (px)

Text of Digitization of Audio.ppt

  • 1.Chapter Overview of Analog and Digital Technologies

2. Chapter Objectives

  • Explain the basic concepts of analog and digital technology
  • Show the importance of frequency spectrum to communication along with an explanation of the concept of bandwidth
  • Give an overview of the interface technology between analog and digital technology
  • Describe the process of digitizing data, audio, image and video
  • Discuss quality retention in digital transmission

3. Chapter Modules

  • Overview of analog technology
  • Frequency spectrum and bandwidth
  • Digital technology
  • Digital-to-Analog and Analog-to-Digital Interfaces
  • Overview of Digitization of Information
  • Digitization of Data
  • Digitization of Audio

Continued 4. Continuation of Chapter Modules

  • Quality retention in digital transmission
  • Digitization of image
  • Digitization of video

5. MODULE Overview of Analog Technology 6. Areas of Application

  • Old telephone networks
  • Most television broadcasting at present
  • Radio broadcasting

7. Analog Signals: The Basics Time Signal Frequency = Cycle/Second A typicalsine wave Cycle Amplitude 8. Amplitude and Cylce

  • Amplitude
    • Distance above reference line
  • Cycle
    • One complete wave

9. Frequency

  • Frequency
    • Cycles per second
    • Hertzis the unit used for expressing frequency
  • Frequency spectrum
    • Defines the bandwidth for different analog communication technologies

10. Information Representation Using Analog Signals

  • Information can be represented using analog signals
  • Analog signals cannot be manipulated easily
  • Analog signals must be digitized for computer processing

11. Analog Digital Conversion 10110100 A to D Converters, Digital Signal Processors (DSP) etc. 12. Data Transmission Example Computer Modem Digital 0s and 1s Analog 0s and 1s Digital-to-Analog Modulation and vice versa 13. Voice Transmission Example Voice Carrier Wave AM Radio Transmission Analog-to-Analog Modulation 14. END OF MODULE 15. MODULEFrequency Spectrum and Bandwidth 16. Frequency Spectrum Defined

  • Available range of frequencies for communication
  • Starts from low frequency communication such as voice and progresses to high frequency communication such as satellite communication
  • The spectrum spans the entire bandwidth of communicable frequencies

17. Frequency Spectrum Low Frequency High Frequency Radio Frequency Coaxial Cable MHz Satellite Transmission Microwave MHz Voice KHz 18. Frequency Spectrum

  • Low-end
    • Voice band
  • Middle
    • Microwave
  • High-end
    • Satellite communication

19. Bandwidth Definition

  • Bandwidth, in general, represents a range of frequencies

300 MHz 700 MHz Bandwidth is 400 MHz 20. Usage of the Term Bandwidth

  • To specify the communication capacity
    • A medium such as a coaxial cable is associated with a bandwidth
  • To indicate the bandwidth of a technology
    • Voice grade circuits have a bandwidth of 4 KHz (0-4000 Hz)

21. Communication Capacity

  • Bandwidth is indicative of the communication capacity
  • Communication speed is proportional to bandwidth
    • Shanons law
  • Units used to represent bandwidth are MHz, Mbps etc.

22. Coaxial Cable Example

  • Bandwidth of 300 MHz
  • Comparison with twisted pair
    • Higher bandwidth
    • Supports faster communication speeds
    • Supports multi-drop connection

Coaxial Cable Multi-drop 23. Limiting Factors onCommunication Speed Communication Speed Bandwidth Technology 24. Continuation of Bandwidth and Technology on Communication Speed

  • Bandwidth limitation
    • Use better technology such as data compression used in modems to increase speed of communication
  • Bandwidth and technology limitation
    • Move to higher bandwidth media such as fiber cables

25. Speed Dependency on Bandwidth and Technology Medium 1 example can beshielded twistedpair and medium 2 example can be fiber. Medium 1 Technology Medium 2 Higher Bandwidth 26. END OF MODULE 27. MODULE An Overview of Digital Technology 28. Areas of Application

  • Computers
  • New telephone networks
  • Phased introduction into television broadcasting

29. Digital Technology

  • Basis
    • Digital signals that could be assigned digital values
  • Digital computer technology
    • Digital signals
    • Binary representation
      • Encoded into ones and zeros

30. Digital Advantage

  • Processing using computer technology
  • Programmable services
  • Better quality due to being able to reconstruct exact digital patterns at the receiving end
  • Faster communication speeds are possible

31. Digital Signal 10110100 Pulse Time Signal Strength Pulse Duration 32. Clock Speed and Pulse Duration Pulse Duration MHz 33. Clock Speed andExecution Speed

  • Pulse duration is inversely proportional to theclock frequency
  • Faster the clock speed, the smaller the pulse duration
  • Smaller the pulse duration, the faster the execution in general

34. Clock Speed and Communication Speed

  • Faster the clock speed, smaller the pulse duration
  • Smaller the pulse duration, smaller the time taken to transmit one bit of information
  • Therefore, faster the clock speed measured in MHz, faster the communication speed measured in Mbps in general

35. END OF MODULE 36. MODULE Digital-to-Analog andAnalog-to-Digital Interfaces 37. The Need for Conversion

  • Analog-to-Digital
    • Connection of a computer to an analog communication line
  • Digital-to-Digital
    • Connection of a computer to a digital ISDN line

38. Digital-to-Analog Interface Comp. Sys. 1 Comp. Sys. 2 Modem Modem Digital Serial RS-232C Digital Serial RS-232C Analog ITU V.90 POTS 39. Digital-to-Digital InterfaceA Comp. Sys. 1 Comp. Sys. 2 ISDN Adapter ISDN Adapter Digital Serial RS-232C Digital Serial RS-232C Digital ISDN 40. END OF MODULE 41. MODULE Overview of Digitization Of Information 42. Module Objectives

  • Define the representations of information
  • Explain the need to digitize
  • State the advantages of digitization

43. Digital Information Processing Data Audio Image Video Digitized and Encoded Digital Transmission 44. The Need to Digitize

  • Essential for computer processing
  • Essential for transmission
    • Entry point to networks is a often a computer
    • An increasing number of communication lines are digital lines

45. The Advantages of Digitization

  • Information could be processed by the computer
  • Easy transmission of information
  • Minimize loss of quality during transmission

46. END OF MODULE 47. MODULE Digitization Of Data 48. Codes Used in the Digitization Of Data

  • Coding Standards
    • ASCII
    • EBCDIC
    • Unicode
  • ASCII Code example
    • A=1000001

49. The Unicode

  • Replace the ASCII coding system in microcomputers
  • All variations of the Latin language
    • English
    • European languages
  • Chinese and Japanese
  • 18 Major languages
    • Eg: Tamil

50. Unicode Possibilities

  • It is a 16-bit code as opposed to the ASCII code that is basically an 8-bit code
  • It is therefore possible to have 65,536 variations in UNICODE

51. Communication With ASCII And EBCDIC

  • Latin languages can be transmitted in coded form
  • Other languages
    • Bit-mapped image transmission
    • Requires considerably more bandwidth
    • An exception is the use of true-type fonts to display the characters of a language not supported by ASCII

52. Communication With Unicode

  • Binary encoded transmission