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1 ## Copyright (C) 2001 Paul Kienzle |
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2 ## |
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3 ## This program is free software; you can redistribute it and/or modify |
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4 ## it under the terms of the GNU General Public License as published by |
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5 ## the Free Software Foundation; either version 2 of the License, or |
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6 ## (at your option) any later version. |
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7 ## |
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8 ## This program is distributed in the hope that it will be useful, |
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9 ## but WITHOUT ANY WARRANTY; without even the implied warranty of |
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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11 ## GNU General Public License for more details. |
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12 ## |
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13 ## You should have received a copy of the GNU General Public License |
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14 ## along with this program; if not, write to the Free Software |
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15 ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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16 |
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17 ## qidx = quantiz(x, table) |
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18 ## Determine position of x in strictly monotonic table. The first |
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19 ## interval, using index 0, corresponds to x <= table(1). |
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20 ## Subsequent intervals are table(i-1) < x <= table(i). |
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21 ## |
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22 ## [qidx, q] = quantiz(x, table, codes) |
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23 ## Associate each interval of the table with a code. Use codes(1) |
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24 ## for x <= table(1) and codes(n+1) for table(n) < x <= table(n+1). |
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25 ## |
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26 ## [qidx, q, d] = quantiz(...) |
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27 ## Compute distortion as mean squared distance of x from the |
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28 ## corresponding table positions. Note that an equally valid |
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29 ## definition of distortion is the distance from the codebook |
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30 ## values. |
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31 function [qidx, q, d] = quantiz (x, table, codes) |
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32 if (nargin < 2 || nargin > 3) |
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33 usage("[qidx, q, d] = quantiz(x, table, codes)"); |
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34 endif |
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35 |
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36 qidx = length(table) - lookup(flipud(table(:)), x); |
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37 if (nargin > 2 && nargout > 1) |
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38 q = codes(qidx + 1); |
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39 endif |
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40 if (nargout > 2) |
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41 warning("distortion is relative to table instead of codes"); |
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42 table = [table(1) ; table(:) ]; |
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43 d = sumsq (x(:) - table(qidx+1)) / length(x); |
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44 endif |
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45 endfunction |
