FreeCalypso > hg > gsm-codec-lib
annotate dev/a2s-regen.c @ 282:9ee8ad3d4d30
frtest: rm gsmfr-hand-test and gsmfr-max-out utils
These hack programs were never properly documented and were written
only as part of a debug chase, in pursuit of a bug that ultimately
turned out to be in our then-hacky patch to osmo-bts-sysmo,
before beginning of proper patches in Osmocom. These hack programs
need to be dropped from the present sw package because they depend
on old libgsm, and we are eliminating that dependency.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 14 Apr 2024 05:44:47 +0000 |
parents | ba737a0203e2 |
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1 /* |
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2 * This program regenerates a G.711 A-law decoding table equivalent to the |
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3 * a2s[] table in the toast_alaw.c module in libgsm/toast; the intent is |
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4 * to check that table for correctness. The "engine" function that does |
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5 * the computation is based on alaw_expand() from ITU-T G.191 STL. |
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6 */ |
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7 |
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8 #include <stdio.h> |
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9 #include <stdlib.h> |
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10 |
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11 static unsigned |
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12 alaw_expand (input) |
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13 unsigned input; |
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14 { |
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15 short ix, mant, iexp; |
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16 |
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17 ix = input ^ (0x0055); /* re-toggle toggled bits */ |
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18 |
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19 ix &= (0x007F); /* remove sign bit */ |
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20 iexp = ix >> 4; /* extract exponent */ |
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21 mant = ix & (0x000F); /* now get mantissa */ |
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22 if (iexp > 0) |
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23 mant = mant + 16; /* add leading '1', if exponent > 0 */ |
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24 |
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25 mant = (mant << 4) + (0x0008); /* now mantissa left justified and */ |
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26 /* 1/2 quantization step added */ |
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27 if (iexp > 1) /* now left shift according exponent */ |
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28 mant = mant << (iexp - 1); |
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29 |
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30 if (input & 0x80) /* invert, if negative sample */ |
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31 return mant; |
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32 else |
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33 return -mant & 0xFFFF; |
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34 } |
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35 |
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36 main(argc, argv) |
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37 char **argv; |
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38 { |
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39 unsigned input, output; |
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40 |
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41 for (input = 0; input < 256; input++) { |
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42 output = alaw_expand(input); |
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43 printf("%6u,", output); |
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44 if ((input & 7) == 7) |
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45 putchar('\n'); |
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46 } |
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47 exit(0); |
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48 } |