quantization4up.220.06

# quantization4up.220.06 - An Introduction to Quantization...

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S. S. Hemami-ECE220 -5-10/22/06 A Better Grade Quantizer (from my perspective) Now we have bin sizes of 52, 8, 8, 12, and 20. This is a nonuniform quantizer . 52 60 80 100 F D C B A Input g (raw grade) Output L=Q(g) (letter grade) 68 S. S. Hemami-ECE220 -6-10/22/06 Other Quantization Examples Temperature as reported to us by the weatherman on TV, weather.com, etc. We are always given temperatures as integers. The actual measured temperatures are quantized with a step size/bin width of 1. Pixel values in digital images. 8-bit images contain values ranging from 0 to 255 ( ). The sensed luminance values, however, are not integers in the camera CCD. Medical images are often quantized to 12 bits instead of 8. 2 8 1 S. S. Hemami-ECE220 -7-10/22/06 Formal Definition An N-point scalar (1 dimensional) quantizer Q is a mapping where R is the real line and is the output set or codebook with size N . Terminology: The output values are also called o utput levels, output points, reproduction values, reconstruction values/points . The input (real line) is partitioned into cells (also called bins ). Q : R C C y 1 y 2 y N , , , { } R y i S. S. Hemami-ECE220 -8-10/22/06 A 7-point Quantizer Not shown on plot are the left/right endpoints of the leftmost/rightmost bins: Note x 2 x 5 x 3 x 4 x 6 x 1 y 4 y 5 y 6 y 2 y 1 input y 3 output x 0 x 7 , + = = x 0 y 1 x 1 y 2 y N x N < < < < < <
S. S. Hemami-ECE220 -9-10/22/06 Operation when . In English, “output a value of when the input is in the range .” We call the range a “bin” or a cell.

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• Spring '05
• JOHNSON

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