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Revision Multimedia Systems 1 Lecture 1 - The Physics of Sound Lecture 2 - The Java Sound API Lecture 3 - Input Transducers (Microphones) Lecture 4 - Output Transducers (Speakers) Lecture 5 - Manipulating Audio (A/D) Lecture 6 - Manipulating Digital Audio (D/A)

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Presentation Transcript

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Multimedia Systems 1

  • Lecture 1 - The Physics of Sound

  • Lecture 2 - The Java Sound API

  • Lecture 3 - Input Transducers (Microphones)

  • Lecture 4 - Output Transducers (Speakers)

  • Lecture 5 - Manipulating Audio (A/D)

  • Lecture 6 - Manipulating Digital Audio (D/A)

  • Lecture 7 - Manipulating Digital Audio (Effects)

  • Lecture 8 - Storing Digital Audio (CD)

  • Lecture 9 - Digital Audio Storage Formats (Wav / MIDI)

  • Lecture 10 - Digital Audio Compression (Perceptual coding)

  • Lecture 11 - PC Audio (Sound cards)

  • Lecture 12 - Issues in Digital Audio (copyright)


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Physics of Sound

  • Sound waves

  • Wavelength, Frequency

  • Bandwidth

  • Bass, Treble, Timbre

  • Amplitude, Decibels

  • Harmonics

  • Superposition, Fourier

  • Multiple channels


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Input Transducers

  • Dynamic and Condensing microphones

    • Construction

    • Principles of operation

    • Advantages/ disadvantages

  • Pick-up patterns

    • Omnidirectional

    • Unidirectional

    • Bidirectional

    • Principles, advantages, disadvantages


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Input Transducers

  • Proximity effect, frequency response

  • Balanced system

    • Principle of operation

    • Common mode rejection

    • Phantom Powering

  • Feedback


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Output Transducers

  • Loudspeakers

    • Components and operation

    • Tweeter, Mid range and woofers

    • Frequency Response

  • Crossovers

    • Passive – low, mid and high pass

    • Active filter

  • Passive and active speakers


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Output Transducers

  • Distortion

    • Intermodulation

    • Harmonic

    • Transient

    • Loudness

  • Enclosures

    • Infinite Baffle

    • Vented Enclosure


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Manipulating Audio

  • The Digital domain

    • Advantages / disadvantages

  • Nyquist

  • Aliasing

  • Low pass filtering

    • Digital

    • Analogue

  • Oversampling


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Manipulating Audio

  • Oversampling


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Manipulating Audio

  • Quantization

    • Levels

    • Noise

    • Error/Accuracy

  • Dithering


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Anti-aliasing filter

Anti-aliasing filter

Sample and Hold

Sample and Hold

A to D Converter

A to D Converter

Manipulating Audio

  • A to D Principal elements

Analogue input (L)

Processing (error correction)

Dither generator

Multiplexer

Analogue input (R)


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Output sample and Hold

Output lowpass filter

D to A Converter

Processing (error correction)

Reproduction demodulation

Demultiplexer

Output sample and Hold

Output lowpass filter

D to A Converter

Manipulating Digital Audio

  • PCM

    • NRZ, NRZI, FM, PE

  • Error Correction

  • D to A Principal elements


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Manipulating Digital Audio

  • D/A conversion

    • Absolute linearity error

    • Differential linearity error

  • Sample and Hold

  • Low pass filtering

  • Oversampling


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Manipulating Digital Audio

  • Effects

    • Delay

    • Echo

    • Reverb

    • Flanging

    • Pitch,Tempo

  • Amplitude envelope, dynamic range

  • Pan and Balance


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Compact Disc

8 bits P,Q,R,S,T,U,V,W

0.163mm

Parity (32 bits)

Parity (32 bits)

Sync (24 bits)

Sub code

Data (96 bits)

Data (96 bits)

1 Frame

Storing Digital Audio

  • Optical storage

    • Advantages/disadvantages

  • Audio CD

    • Frame structure and operation

    • Audio data

    • Sync word

    • Parity

    • Subcode


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Storing Digital Audio

  • Audio CD

    • Eight to Fourteen Modulation

      • Reasons

      • Structure


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Storing Digital Audio

  • CD-ROM Data Block

    • Structure

    • Why extra EDC/ECC

  • DAT

  • Mini Disc


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Digital Audio Storage Formats

  • Wave, Au, Aiff

    • Descriptor

    • Format information

    • Data

  • MIDI

    • Advantages/ disadvantages

    • Message Format

      • Status byte, Data byte

    • General MIDI

    • Sequencers


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Digital Audio Compression

  • Psychoacoustics

  • Threshold of Hearing & Masking


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Digital Audio Compression

  • Amplitude Masking

  • Critical Bands

  • Temporal Masking

  • Perceptual Coding

    • Conceptual operation

  • Joint Stereo Coding

  • MP3


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PC Audio

  • Sound Card Components

    • Digital I/O

    • CD Analogue Audio Input

    • Line in/out

  • Digital Audio Extraction

    • Advantages/ disadvantages

  • Synthesis

    • FM

    • Wave table


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Issues in Digital Audio

  • Intellectual Property

  • Copyright

    • Fair Use – Four factors

    • Exceptions

    • Sampling

    • Ownership

    • Licensing

    • Napster


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Fin

Fin


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