18 Digital Information, Sampling - ECE 110 M.-C. Brunet...

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ECE 110 M.-C. Brunet Digital Information and Sampling Handout 18 Digital Information : ampling Sampling To use digital technology (as opposed to analog) To represent various types of information. Goal Digital cameras, CDs, DVDs, … Applications Digitization: Analog signal Æ Digital signal (A/D converter) Sampling Quantization + Measuring a continuous Deciding how many Digitization: object at uniformly separated units (samples) and assigning a value to each sample digits to use per sampled value, and how to assign them M.-C. BRUNET ECE 110 UIUC 18.1
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ECE 110 M.-C. Brunet Digital Information and Sampling Handout 18 Definitions l Sample: Sampling Size: Sampling Rate: Uniform sampling unit Dimension of the sample 1/ sampling size = number of samples per unit of number of samples per unit of Time (in 1D, or 3D) Length (in 2D) Examples Sample Type Sample time interval cell or ixel temporal spatial sine waves audio signals (speech, music) a painting, text, r photograph 1D 2D hoice of Sampling Rate? pixel image or frame temporal or photograph a movie 3D M.-C. BRUNET ECE 110 UIUC 18.2 Choice of Sampling Rate? Important & difficult Æ Quality of signal vs storage if Rate ^, Quality ^, but Storage ^ too Applications 1D Applications Music! MP3, etc… www.nonstopmac.com/ipod Digital Signal Processing (theory). Speech recognition gizmodo.com Digital Imaging Applications www.idiap.ch Computer animation in movie industry. Photography, and art. www.mediaspin.com Robotics: automatic visual recognition. M.-C. BRUNET ECE 110 UIUC 18.3 ase.tufts.edu /roboticsacademy /Robotics.htm
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ECE 110 M.-C. Brunet Digital Information and Sampling Handout 18 1D Sampling Definitions Temporal sampling of a waveform = process of cording values at distinct time points (uniformly recording values at distinct time points (uniformly spaced) along a signal. Sampling size = sampling period = uniform spacing in time between two adjacent samples Æ Ts (unit is second) Sampling rate = sampling frequency = number of samples per second Æ fs = 1/Ts (unit is Hertz) Example 1 : Music is usually sampled at a rate of 44.1 kHz (44,100 samples per second). M.-C. BRUNET ECE 110 UIUC 18.4 Notes of higher frequency Æ higher pitch A Sequence = an ordered set of numbers. A/D From Analog to Digital (Sampling) q A sequence of samples is the set of numerical sampled values of a signal s(t). S = { s(0), s(Ts), s(2Ts), s(3Ts), …} Ts is the sampling size. nalog s(t) s[5] s[4] Analog signal Digital signal s[0] s[1] s[2] s[3] Ts 2Ts 3Ts 4Ts 5Ts t 0 With s[n] = s(nTs) the sequence is also: S = { s[0], s[1], s[2], s[3], …} ( digital signal ) (same values, simply different notations) M.-C. BRUNET ECE 110 UIUC 18.5 See Example 2. (for more examples see Mallard tutorials, and lecture notes).
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ECE 110 M.-C. Brunet Digital Information and Sampling Handout 18 Example 2 : The sound signal of a tuning fork A/D From Analog to Digital (Sampling) (or of a flute, or of a person whistling) is almost a perfect sinusoid. Below is one possible graph for it.
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This note was uploaded on 09/16/2009 for the course ECE 110 taught by Professor Haken during the Spring '08 term at University of Illinois at Urbana–Champaign.

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18 Digital Information, Sampling - ECE 110 M.-C. Brunet...

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