FreeCalypso > hg > gsm-codec-lib

annotate dev/s2u-regen-plus4.c @ 282:9ee8ad3d4d30

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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>
date Sun, 14 Apr 2024 05:44:47 +0000
parents 67d60915fbbe
children
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1 /*
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2 * This program is a companion to s2u-regen.c: it computes a mu-law encoding
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3 * table with 13-bit input just like s2u-regen, but computes it as if the
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4 * lsb following the 13-bit part is always 1 rather than always 0. The
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5 * purpose of this program is to illustrate the effect of that lsb on the
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6 * mu-law output.
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7 */
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8
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9 #include <stdio.h>
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10 #include <stdlib.h>
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12 static unsigned
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13 ulaw_compress(input)
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14 unsigned input;
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15 {
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16 short i; /* aux.var. */
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17 short absno; /* absolute value of linear (input) sample */
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18 short segno; /* segment (Table 2/G711, column 1) */
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19 short low_nibble; /* low nibble of log companded sample */
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20 short high_nibble; /* high nibble of log companded sample */
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21 unsigned output;
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22
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23 /* -------------------------------------------------------------------- */
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24 /* Input is 14-bit right-justified in this version */
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25 /* Compute absolute value; adjust for easy processing */
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26 /* -------------------------------------------------------------------- */
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27 absno = input >= 0x2000 /* compute 1's complement in case of */
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28 ? (~input & 0x1FFF) + 33 /* negative samples */
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29 : input + 33; /* NB: 33 is the difference value */
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30 /* between the thresholds for */
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31 /* A-law and u-law. */
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32 if (absno > (0x1FFF)) /* limitation to "absno" < 8192 */
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33 absno = (0x1FFF);
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34
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35 /* Determination of sample's segment */
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36 i = absno >> 6;
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37 segno = 1;
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38 while (i != 0) {
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39 segno++;
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40 i >>= 1;
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41 }
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42
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43 /* Mounting the high-nibble of the log-PCM sample */
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44 high_nibble = (0x0008) - segno;
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46 /* Mounting the low-nibble of the log PCM sample */
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47 low_nibble = (absno >> segno) /* right shift of mantissa and */
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48 &(0x000F); /* masking away leading '1' */
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49 low_nibble = (0x000F) - low_nibble;
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51 /* Joining the high-nibble and the low-nibble of the log PCM sample */
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52 output = (high_nibble << 4) | low_nibble;
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53
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54 /* Add sign bit */
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55 if (input < 0x2000)
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56 output = output | (0x0080);
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57
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58 return output;
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59 }
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61 main(argc, argv)
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62 char **argv;
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63 {
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64 unsigned input, output;
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65
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66 for (input = 0; input < 8192; input++) {
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67 output = ulaw_compress((input << 1) + 1);
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68 printf("%04o,", output);
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69 if ((input % 15) == 14 || input == 8191)
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70 putchar('\n');
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71 }
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72 exit(0);
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73 }