From Analogue to Digital: From Analogue to Digital: From Analogue - - PowerPoint PPT Presentation

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From Analogue to Digital: From Analogue to Digital: From Analogue - - PowerPoint PPT Presentation

Nov 08, 2023 164 likes •457 views

From Analogue to Digital: From Analogue to Digital: From Analogue to Digital: Concepts and Techniques Concepts and Techniques Concepts and Techniques

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SLIDE 1

Audiovisual Compression: from Basics to Systems, Fernando Pereira

From Analogue to Digital: Concepts and Techniques

  • Klagenfurt, Austria, October 2008

From Analogue to Digital: From Analogue to Digital: Concepts and Techniques Concepts and Techniques

  • Klagenfurt, Austria, October 2008
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SLIDE 2

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Digitization Digitization Digitization

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SLIDE 3

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Sampling or Time Discretization Sampling or Sampling or Time Time Discretization Discretization

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Sampling is governed by the Sampling Theorem which states that: An analog signal may be fully reconstructed from a periodic sequence of samples if the sampling frequency is, at least, twice the maximum frequency present in the signal.

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SLIDE 4

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Quantization or Amplitude Discretization Quantization or Quantization or Amplitude Amplitude Discretization Discretization

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SLIDE 5

Audiovisual Compression: from Basics to Systems, Fernando Pereira

2 Levels Quantization 2 Levels Quantization 2 Levels Quantization

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SLIDE 6

Audiovisual Compression: from Basics to Systems, Fernando Pereira

4 Levels Quantization 4 Levels Quantization 4 Levels Quantization

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SLIDE 7

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Uniform Quantization Uniform Quantization Uniform Quantization

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SLIDE 8

Audiovisual Compression: from Basics to Systems, Fernando Pereira

(on)Uniform Quantization (on (on) )Uniform Quantization Uniform Quantization

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SLIDE 9

Audiovisual Compression: from Basics to Systems, Fernando Pereira

(PCM)

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SLIDE 10

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Digital TV: an Example Digital TV: an Ex Digital TV: an Exa ampl mple e

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SLIDE 11

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Why Compressing ? Why Compressing ? Why Compressing ?

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SLIDE 12

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Digital Source Coding/Compression Digital Source Coding/Compression Digital Source Coding/Compression

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  • Example 1: Maximizing the

quality for the available rate

Example 2: Minimizing the rate

for a target quality

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SLIDE 13

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Source Coding: Original Data, Symbols and Bits Source Source Codi Coding ng: : Original Data, Symbols and Original Data, Symbols and Bits Bits

Symbol Generator (Model) Entropy Coder

Original data, e.g. PCM bits Symbols Compressed bits

The encoder represents the original digital data (PCM) as a sequence of symbols, and later bits, using in the best way the set of available coding tools to satisfy the relevant requirements.

The encoder The encoder extracts from original data extracts from original data ‘ ‘its best its best’ ’ ... ...

Encoder

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SLIDE 14

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Coding … and Decoding ... Coding Coding … … and D and Decoding ecoding ... ...

Encoder Decoder

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SLIDE 15

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Efficient Digitization: Sampling + Quantization + Source Coding Efficient Digitization: Sampling + Efficient Digitization: Sampling + Quantization + Source Coding Quantization + Source Coding

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SLIDE 16

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Digital Image Coding: Main Types Digital Digital Image Image Coding: Main Types Coding: Main Types

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SLIDE 17

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Where does Compression come from ? Where does Compression come from ? Where does Compression come from ?

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SLIDE 18

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Compression Metrics Compression Metrics Compression Metrics

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SLIDE 19

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Human Visual System Human Human Visual Visual System System

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SLIDE 20

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Human Auditory System Human Auditory System Human Auditory System

It is essential to keep in mind that audio/speech information is to be consumed by the Human Auditory System ! The Human Auditory System is the client that must be satisfied in terms of audio quality!

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SLIDE 21

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Quality Metrics Quality Metrics Quality Metrics

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SLIDE 22

Audiovisual Compression: from Basics to Systems, Fernando Pereira

How Does PS(R Fail … How Does PS(R Fail How Does PS(R Fail … …

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SLIDE 23

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Channel Coding Channel Coding Channel Coding

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Codes

Symbols with useful information Correcting symbols m k n R = m/n = 1 – k/n

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SLIDE 24

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Digital Modulation Digital Modulation Digital Modulation

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SLIDE 25

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Selecting a Modulation ... Selecting a Modulation ... Selecting a Modulation ...

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SLIDE 26

Audiovisual Compression: from Basics to Systems, Fernando Pereira

64)QAM Modulation Constelation 64 64) )QAM Modulation Constelation QAM Modulation Constelation

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SLIDE 27

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Digital TV: a Full Example Digital TV: a Full Ex Digital TV: a Full Exa ampl mple e

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SLIDE 28

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Typical Digital Transmission Chain ... Typical Digital Transmission Chain ... Typical Digital Transmission Chain ...

Digitalization Source Coding Channel Coding Modulation

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SLIDE 29

Audiovisual Compression: from Basics to Systems, Fernando Pereira

Bibliography Bibliography Bibliography

Fundamentals of Digital Image Processing

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Digital Video Processing= A:

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