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annotate dev/s2u-regen.c @ 585:3c6bf0d26ee7 default tip

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TW-TS-005 reader: fix maximum line length bug TW-TS-005 section 4.1 states: The maximum allowed length of each line is 80 characters, not including the OS-specific newline encoding. The implementation of this line length limit in the TW-TS-005 hex file reader function in the present suite was wrong, such that lines of the full maximum length could not be read. Fix it. Note that this bug affects comment lines too, not just actual RTP payloads. Neither Annex A nor Annex B features an RTP payload format that goes to the maximum of 40 bytes, but if a comment line goes to the maximum allowed length of 80 characters not including the terminating newline, the bug will be triggered, necessitating the present fix.
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 25 Feb 2025 07:49:28 +0000
parents a5200ad12d58
children
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1 /*
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2 * This program generates a G.711 mu-law encoding table of the same form
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3 * as the s2u[] table in the toast_ulaw.c module in libgsm/toast, i.e.,
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4 * an encoding table that takes only the upper 13 bits of the linear PCM
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5 * sample to be encoded, even though canonical mu-law encoding requires
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6 * 14-bit input. The 13-bit table constructed by this program is computed
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7 * as if the lsb of the "proper" 14-bit input is always zero, like it is
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8 * expected to be when the linear PCM samples came from the output of a
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9 * GSM speech decoder.
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10 *
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11 * The "engine" function that does the computation is based on ulaw_compress()
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12 * from ITU-T G.191 STL.
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13 */
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15 #include <stdio.h>
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16 #include <stdlib.h>
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18 static unsigned
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19 ulaw_compress(input)
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20 unsigned input;
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21 {
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22 short i; /* aux.var. */
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23 short absno; /* absolute value of linear (input) sample */
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24 short segno; /* segment (Table 2/G711, column 1) */
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25 short low_nibble; /* low nibble of log companded sample */
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26 short high_nibble; /* high nibble of log companded sample */
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27 unsigned output;
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29 /* -------------------------------------------------------------------- */
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30 /* Input is 14-bit right-justified in this version */
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31 /* Compute absolute value; adjust for easy processing */
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32 /* -------------------------------------------------------------------- */
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33 absno = input >= 0x2000 /* compute 1's complement in case of */
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34 ? (~input & 0x1FFF) + 33 /* negative samples */
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35 : input + 33; /* NB: 33 is the difference value */
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36 /* between the thresholds for */
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37 /* A-law and u-law. */
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38 if (absno > (0x1FFF)) /* limitation to "absno" < 8192 */
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39 absno = (0x1FFF);
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40
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41 /* Determination of sample's segment */
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42 i = absno >> 6;
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43 segno = 1;
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44 while (i != 0) {
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45 segno++;
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46 i >>= 1;
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47 }
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49 /* Mounting the high-nibble of the log-PCM sample */
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50 high_nibble = (0x0008) - segno;
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52 /* Mounting the low-nibble of the log PCM sample */
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53 low_nibble = (absno >> segno) /* right shift of mantissa and */
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54 &(0x000F); /* masking away leading '1' */
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55 low_nibble = (0x000F) - low_nibble;
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56
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57 /* Joining the high-nibble and the low-nibble of the log PCM sample */
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58 output = (high_nibble << 4) | low_nibble;
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59
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60 /* Add sign bit */
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61 if (input < 0x2000)
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62 output = output | (0x0080);
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63
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64 return output;
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65 }
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67 main(argc, argv)
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68 char **argv;
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69 {
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70 unsigned input, output;
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71
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72 for (input = 0; input < 8192; input++) {
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73 output = ulaw_compress(input << 1);
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74 printf("%04o,", output);
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75 if ((input % 15) == 14 || input == 8191)
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76 putchar('\n');
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77 }
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78 exit(0);
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79 }