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annotate libgsmhr1/rtp_in.c @ 492:cc3a831712a4

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libgsmhr1: implement arbitrary RTP input
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 15 Jun 2024 06:52:37 +0000
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492
cc3a831712a4 libgsmhr1: implement arbitrary RTP input
Mychaela Falconia <falcon@freecalypso.org>
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1 /*
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2 * The function implemented in this module takes whatever HRv1 payload format
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3 * came in from RTP (can be RFC 5993 with or without TW-TS-002 extensions,
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4 * can be bare TS 101 318, can be zero-length or missing payload) and turns it
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5 * into canonical TW-TS-002 format, be it for storage or for immediate
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6 * further processing.
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7 */
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8
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9 #include <stdint.h>
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10 #include <string.h>
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11 #include "tw_gsmhr.h"
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12
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13 int gsmhr_rtp_in_preen(const uint8_t *rtp_in, unsigned rtp_in_len,
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14 uint8_t *canon_pl)
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15 {
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16 int ft;
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17
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18 switch (rtp_in_len) {
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19 case 0:
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20 /* BFI-no-data, but not an invalid RTP input per se */
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21 canon_pl[0] = 0x70;
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22 return 0;
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23 case 1:
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24 /*
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25 * This length is valid only if the payload is in
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26 * RFC 5993 or TW-TS-002 format with FT=1 or FT=7.
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27 */
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28 if (rtp_in[0] & 0x80)
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29 goto bad_rtp_input;
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30 ft = rtp_in[0] >> 4;
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31 if (ft == 1 || ft == 7) {
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32 canon_pl[0] = rtp_in[0];
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33 return 0;
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34 } else
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35 goto bad_rtp_input;
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36 case GSMHR_FRAME_LEN_RPF:
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37 /*
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38 * The length is that of a TS 101 318 payload.
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39 * No further checks can be done: every possible
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40 * bit pattern is a valid payload in this format.
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41 * But we do need to check for a perfect SID
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42 * (the only kind of SID this format allows)
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43 * and mark it accordingly in the output.
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44 */
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45 canon_pl[0] = gsmhr_ts101318_is_perfect_sid(rtp_in) << 4;
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46 memcpy(canon_pl + 1, rtp_in, GSMHR_FRAME_LEN_RPF);
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47 return 0;
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48 case GSMHR_FRAME_LEN_5993:
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49 /*
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50 * This length is valid only if the payload is in
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51 * RFC 5993 or TW-TS-002 format with FT=0, FT=2 or FT=6.
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52 */
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53 if (rtp_in[0] & 0x80)
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54 goto bad_rtp_input;
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55 ft = rtp_in[0] >> 4;
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56 if (ft == 0 || ft == 2 || ft == 6) {
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57 memcpy(canon_pl, rtp_in, GSMHR_FRAME_LEN_5993);
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58 return 0;
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59 } else
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60 goto bad_rtp_input;
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61 default:
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62 bad_rtp_input:
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63 /*
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64 * Treat it like BFI-no-data, and tell the caller
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65 * that we received an invalid RTP payload.
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66 */
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67 canon_pl[0] = 0x70;
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68 return -1;
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69 }
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70 }