Revision

1. Revision

2. 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)

3. Physics of Sound • Sound waves • Wavelength, Frequency • Bandwidth • Bass, Treble, Timbre • Amplitude, Decibels • Harmonics • Superposition, Fourier • Multiple channels

4. Input Transducers • Dynamic and Condensing microphones • Construction • Principles of operation • Advantages/ disadvantages • Pick-up patterns • Omnidirectional • Unidirectional • Bidirectional • Principles, advantages, disadvantages

5. Input Transducers • Proximity effect, frequency response • Balanced system • Principle of operation • Common mode rejection • Phantom Powering • Feedback

6. 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

7. Output Transducers • Distortion • Intermodulation • Harmonic • Transient • Loudness • Enclosures • Infinite Baffle • Vented Enclosure

8. Manipulating Audio • The Digital domain • Advantages / disadvantages • Nyquist • Aliasing • Low pass filtering • Digital • Analogue • Oversampling

9. Manipulating Audio • Oversampling

10. Manipulating Audio • Quantization • Levels • Noise • Error/Accuracy • Dithering

11. 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)

12. 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

13. Manipulating Digital Audio • D/A conversion • Absolute linearity error • Differential linearity error • Sample and Hold • Low pass filtering • Oversampling

14. Manipulating Digital Audio • Effects • Delay • Echo • Reverb • Flanging • Pitch,Tempo • Amplitude envelope, dynamic range • Pan and Balance

15. 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

16. Storing Digital Audio • Audio CD • Eight to Fourteen Modulation • Reasons • Structure

17. Storing Digital Audio • CD-ROM Data Block • Structure • Why extra EDC/ECC • DAT • Mini Disc

18. Digital Audio Storage Formats • Wave, Au, Aiff • Descriptor • Format information • Data • MIDI • Advantages/ disadvantages • Message Format • Status byte, Data byte • General MIDI • Sequencers

19. Digital Audio Compression • Psychoacoustics • Threshold of Hearing & Masking

20. Digital Audio Compression • Amplitude Masking • Critical Bands • Temporal Masking • Perceptual Coding • Conceptual operation • Joint Stereo Coding • MP3

21. PC Audio • Sound Card Components • Digital I/O • CD Analogue Audio Input • Line in/out • Digital Audio Extraction • Advantages/ disadvantages • Synthesis • FM • Wave table

22. Issues in Digital Audio • Intellectual Property • Copyright • Fair Use – Four factors • Exceptions • Sampling • Ownership • Licensing • Napster

23. Fin Fin