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1636
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1 function y = mu2lin (x, bit) |
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2 |
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3 # usage: y = mu2lin (x [, bit]) |
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4 # |
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5 # If x is a vector of audio data with mu-law encoding, mu2lin (x) |
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6 # holds the same data with linear encoding. |
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7 # The optional argument bit specifies whether the input data is |
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8 # 8 bit (default) or 16 bit. |
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9 |
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10 # Written by AW (Andreas.Weingessel@ci.tuwien.ac.at) on Oct 18, 1994 |
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11 # Updated by AW (Andreas.Weingessel@ci.tuwien.ac.at) on Oct 27, 1994 |
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12 # Copyright Department of Probability Theory and Statistics TU Wien |
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13 |
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14 if (nargin == 1) |
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15 bit = 8; |
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16 elseif (nargin == 2) |
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17 if (bit != 8 && bit != 16) |
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18 error ("mu2lin: bit must be either 8 or 16"); |
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19 endif |
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20 else |
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21 usage ("y = mu2lin (x [, bit])"); |
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22 endif |
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23 |
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24 if (! is_vector (x)) |
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25 error ("mu2lin: x must be a vector"); |
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26 endif |
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27 |
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28 exp_lut = [0; 132; 396; 924; 1980; 4092; 8316; 16764]; |
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29 |
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30 # invert x bitwise |
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31 x = 255 - x; |
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32 |
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33 # determine sign of y |
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34 sig = (x > 127); |
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35 |
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36 # determine exponent and fraction of y |
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37 e = fix (x / 16) - 8 .* sig + 1; |
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38 f = rem (x, 16); |
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39 |
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40 sig = 1 - 2 .* sig; |
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41 y = (pow2 (f, e + 2) + exp_lut (e)) .* sig; |
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42 |
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43 # convert to 8-bit |
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44 if (bit == 8) |
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45 ld = max (abs (y)); |
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46 if (ld < 16384) |
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47 sc = 64 / ld; |
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48 else |
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49 sc = 1 / 256; |
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50 endif |
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51 y = fix (y * sc); |
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52 endif |
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53 |
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54 endfunction |
