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annotate dev/s2u-regen-plus4.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 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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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 }