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annotate dev/u2s-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 20750ffb1c3e
children
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1 /*
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2 * This program generates a G.711 mu-law decoding table of the same form
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3 * as the u2s[] table in the toast_ulaw.c module in libgsm/toast; the intent
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4 * is to replace that incorrect table with a corrected one. The "engine"
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5 * function that does the computation is based on ulaw_expand() from ITU-T
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6 * G.191 STL.
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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_expand (input)
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14 unsigned input;
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15 {
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16 short segment; /* segment (Table 2/G711, column 1) */
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17 short mantissa; /* low nibble of log companded sample */
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18 short exponent; /* high nibble of log companded sample */
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19 short sign; /* sign of output sample */
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20 short step;
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21 short output;
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23 sign = input < (0x0080) /* sign-bit = 1 for positiv values */
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24 ? -1 : 1;
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25 mantissa = ~input; /* 1's complement of input value */
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26 exponent = (mantissa >> 4) & (0x0007); /* extract exponent */
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27 segment = exponent + 1; /* compute segment number */
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28 mantissa = mantissa & (0x000F); /* extract mantissa */
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29
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30 /* Compute Quantized Sample (14 bit left justified!) */
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31 step = (4) << segment; /* position of the LSB */
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32 /* = 1 quantization step) */
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33 output = sign * /* sign */
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34 (((0x0080) << exponent) /* '1', preceding the mantissa */
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35 +step * mantissa /* left shift of mantissa */
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36 + step / 2 /* 1/2 quantization step */
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37 - 4 * 33);
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38 return output & 0xFFFF;
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39 }
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41 main(argc, argv)
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42 char **argv;
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43 {
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44 unsigned input, output;
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45
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46 for (input = 0; input < 256; input++) {
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47 output = ulaw_expand(input);
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48 printf("%6u,", output);
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49 if ((input & 7) == 7)
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50 putchar('\n');
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51 }
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52 exit(0);
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53 }