lecture3 - CSE 471 Media Processing and Multimedia Sampling...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
1 CSE 471 Media Processing and Multimedia Sampling and Quantization Capturing sounds electronically Sampling sounds Aliasing Quantization
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 CSE 471 Media Processing and Multimedia Electronic capture of sounds N S
Background image of page 2
3 CSE 471 Media Processing and Multimedia Sampling Sampling - simply taking voltage readings at fixed points in time Uniform sampling – sampling at regular intervals
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 CSE 471 Media Processing and Multimedia Sampling Real values at fixed points in time Uses a “sample-and-hold” Values are called “samples” Analog signal Sample and Hold Sampled signal Sample
Background image of page 4
5 CSE 471 Media Processing and Multimedia How might you measure waves on a beach? Or, even, sample the wave height
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 CSE 471 Media Processing and Multimedia Is sampling okay? Question: Is a sampled representation the same thing? Yes, provided…
Background image of page 6
7 CSE 471 Media Processing and Multimedia The Sampling Theorem Given a uniform sample rate of f s , the highest frequency that can be unambiguously represented is f s /2 f s /2 is the Nyquist Frequency CD Players use f s =44,100 samples/sec The Nyquist Frequency is 22,050 Hz Why don’t CD’s sample at 40KHz?
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 CSE 471 Media Processing and Multimedia Sound in the Real World Recall: All sounds can be expressed as a combination of sinusoids String instruments generate harmonics C8 on piano = 4186 Hz 6 th Harmonic is 25,116 Hz Above the Nyquist Frequency!! Many instruments generate content above 20 KHz ( 29 = + = 1 sin ) ( h h h t h c t f φ ϖ
Background image of page 8
9 CSE 471 Media Processing and Multimedia What happens above Nyquist Frequency? For now, we’ll use the term Aliasing
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 07/25/2008 for the course CSE 471 taught by Professor Owen during the Fall '07 term at Michigan State University.

Page1 / 31

lecture3 - CSE 471 Media Processing and Multimedia Sampling...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online