FreeCalypso > hg > gsm-codec-lib
annotate libgsmefr/sid_class.c @ 132:3fd48946dcb8
doc/EFR-testing article written
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 11 Dec 2022 05:12:02 +0000 |
parents | b5726d659915 |
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1 /* |
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2 * EFR_sid_classify() utility function classifies an EFR frame |
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3 * in RTP encoding according to the rules of GSM 06.81 section 6.1.1, |
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4 * judging it as SID=0, SID=1 or SID=2. |
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5 */ |
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6 |
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7 #include "gsm_efr.h" |
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8 |
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9 static const uint8_t SID_codeword_bit_idx[95] = |
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10 { |
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11 45, 46, 48, 49, 50, 51, 52, 53, 54, 55, |
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12 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, |
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13 66, 67, 68, 94, 95, 96, 98, 99, 100, 101, |
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14 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, |
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15 112, 113, 114, 115, 116, 117, 118, 148, 149, 150, |
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16 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, |
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17 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, |
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18 171, 196, 197, 198, 199, 200, 201, 202, 203, 204, |
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19 205, 206, 207, 208, 209, 212, 213, 214, 215, 216, |
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20 217, 218, 219, 220, 221 |
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21 }; |
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22 |
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23 static inline int get_bit(const uint8_t *frame, unsigned bitnum) |
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24 { |
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25 unsigned bytenum = bitnum >> 3; |
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26 unsigned bit_in_byte = 7 - (bitnum & 7); |
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27 unsigned bitmask = 1 << bit_in_byte; |
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28 |
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29 if (frame[bytenum] & bitmask) |
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30 return 1; |
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31 else |
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32 return 0; |
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33 } |
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34 |
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35 int EFR_sid_classify(const uint8_t *frame) |
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36 { |
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37 unsigned idx, n; |
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38 |
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39 n = 0; |
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40 for (idx = 0; idx < 95; idx++) { |
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41 if (!get_bit(frame, SID_codeword_bit_idx[idx] + 4)) |
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42 n++; |
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43 if (n >= 16) |
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44 return 0; |
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45 } |
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46 if (n < 2) |
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47 return 2; |
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48 else |
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49 return 1; |
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50 } |