Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 1 | /* |
| 2 | * (C) 2017 by sysmocom - s.f.m.c. GmbH |
| 3 | * (C) 2017 by Philipp Maier <pmaier@sysmocom.de> |
| 4 | * |
| 5 | * All Rights Reserved |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License as published by |
| 9 | * the Free Software Foundation; either version 2 of the License, or |
| 10 | * (at your option) any later version. |
| 11 | * |
| 12 | * This program is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | * GNU General Public License for more details. |
| 16 | * |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 17 | */ |
| 18 | |
| 19 | #include <stdbool.h> |
| 20 | #include <string.h> |
| 21 | #include <stdint.h> |
| 22 | #include <errno.h> |
| 23 | |
| 24 | #include <osmocom/core/bitvec.h> |
| 25 | |
| 26 | #include <osmocom/codec/gsm610_bits.h> |
| 27 | #include <osmocom/codec/codec.h> |
| 28 | #include <osmocom/codec/ecu.h> |
| 29 | |
| 30 | /* See also GSM 06.11, chapter 6 Example solution */ |
| 31 | #define GSM610_XMAXC_REDUCE 4 |
| 32 | #define GSM610_XMAXC_LEN 6 |
| 33 | |
| 34 | /** |
| 35 | * Reduce the XMAXC field. When the XMAXC field reaches |
| 36 | * zero the function will return true. |
| 37 | */ |
| 38 | static bool reduce_xmaxcr(struct bitvec *frame_bitvec, |
| 39 | const unsigned int index) |
| 40 | { |
| 41 | unsigned int field_index; |
| 42 | uint64_t field; |
| 43 | |
| 44 | field_index = index; |
| 45 | field = bitvec_read_field(frame_bitvec, &field_index, GSM610_XMAXC_LEN); |
| 46 | if (field > GSM610_XMAXC_REDUCE) |
| 47 | field -= GSM610_XMAXC_REDUCE; |
| 48 | else |
| 49 | field = 0; |
| 50 | |
| 51 | field_index = index; |
| 52 | bitvec_write_field(frame_bitvec, &field_index, field, GSM610_XMAXC_LEN); |
| 53 | |
| 54 | return field == 0; |
| 55 | } |
| 56 | |
| 57 | /** |
| 58 | * Reduce all XMAXC fields in the frame. When all XMAXC fields |
| 59 | * reach zero, then the function will return true. |
| 60 | */ |
| 61 | static bool reduce_xmaxcr_all(struct bitvec *frame_bitvec) |
| 62 | { |
Pau Espin Pedrol | 9bb966a | 2018-07-20 13:58:52 +0200 | [diff] [blame] | 63 | bool silent = true; |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 64 | |
Pau Espin Pedrol | 9bb966a | 2018-07-20 13:58:52 +0200 | [diff] [blame] | 65 | silent &= reduce_xmaxcr(frame_bitvec, GSM610_RTP_XMAXC00); |
| 66 | silent &= reduce_xmaxcr(frame_bitvec, GSM610_RTP_XMAXC10); |
| 67 | silent &= reduce_xmaxcr(frame_bitvec, GSM610_RTP_XMAXC20); |
| 68 | silent &= reduce_xmaxcr(frame_bitvec, GSM610_RTP_XMAXC30); |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 69 | |
| 70 | return silent; |
| 71 | } |
| 72 | |
| 73 | /* Use certain modifications to conceal the errors in a full rate frame */ |
| 74 | static int conceal_frame(uint8_t *frame) |
| 75 | { |
| 76 | struct bitvec *frame_bitvec; |
| 77 | unsigned int len; |
| 78 | bool silent; |
| 79 | int rc = 0; |
| 80 | |
| 81 | /* In case we already deal with a silent frame, |
| 82 | * there is nothing to, we just abort immediately */ |
| 83 | if (osmo_fr_check_sid(frame, GSM_FR_BYTES)) |
| 84 | return 0; |
| 85 | |
| 86 | /* Attempt to allocate memory for bitvec */ |
| 87 | frame_bitvec = bitvec_alloc(GSM_FR_BYTES, NULL); |
| 88 | if (!frame_bitvec) |
| 89 | return -ENOMEM; |
| 90 | |
| 91 | /* Convert a frame to bitvec */ |
| 92 | len = bitvec_unpack(frame_bitvec, frame); |
| 93 | if (len != GSM_FR_BYTES) { |
| 94 | rc = -EIO; |
| 95 | goto leave; |
| 96 | } |
| 97 | |
| 98 | /* Fudge frame parameters */ |
| 99 | silent = reduce_xmaxcr_all(frame_bitvec); |
| 100 | |
| 101 | /* If we reached silence level, mute the frame |
| 102 | * completely, this also means that we can |
| 103 | * save the bitvec_pack operation */ |
| 104 | if (silent) { |
| 105 | memset(frame, 0x00, GSM_FR_BYTES); |
| 106 | frame[0] = 0xd0; |
| 107 | goto leave; |
| 108 | } |
| 109 | |
| 110 | /* Convert back to packed byte form */ |
| 111 | len = bitvec_pack(frame_bitvec, frame); |
| 112 | if (len != GSM_FR_BYTES) { |
| 113 | rc = -EIO; |
| 114 | goto leave; |
| 115 | } |
| 116 | |
| 117 | leave: |
| 118 | bitvec_free(frame_bitvec); |
| 119 | return rc; |
| 120 | } |
| 121 | |
Sylvain Munaut | 35f8ba0 | 2019-05-15 17:34:13 +0200 | [diff] [blame] | 122 | /*! |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 123 | * To be called when a good frame is received. |
| 124 | * This function will then create a backup of the frame |
| 125 | * and reset the internal state. |
Sylvain Munaut | 35f8ba0 | 2019-05-15 17:34:13 +0200 | [diff] [blame] | 126 | * \param[in] state The state object for the ECU |
| 127 | * \param[out] frame The valid frame (GSM_FR_BYTES bytes in RTP payload format) |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 128 | */ |
Harald Welte | c144f3a | 2019-08-01 20:02:40 +0200 | [diff] [blame] | 129 | void osmo_ecu_fr_reset(struct osmo_ecu_fr_state *state, const uint8_t *frame) |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 130 | { |
| 131 | state->subsequent_lost_frame = false; |
| 132 | memcpy(state->frame_backup, frame, GSM_FR_BYTES); |
| 133 | } |
| 134 | |
Sylvain Munaut | 35f8ba0 | 2019-05-15 17:34:13 +0200 | [diff] [blame] | 135 | /*! |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 136 | * To be called when a bad frame is received. |
| 137 | * This function will then generate a replacement frame |
| 138 | * that can be used to conceal the dropout. |
Sylvain Munaut | 35f8ba0 | 2019-05-15 17:34:13 +0200 | [diff] [blame] | 139 | * \param[in] state The state object for the ECU |
| 140 | * \param[out] frame The buffer to fill with GSM_FR_BYTES of replacement frame |
| 141 | * \returns 0 if the frame was sucessfully filled |
Philipp Maier | 40def49 | 2017-12-16 03:42:15 +0700 | [diff] [blame] | 142 | */ |
| 143 | int osmo_ecu_fr_conceal(struct osmo_ecu_fr_state *state, uint8_t *frame) |
| 144 | { |
| 145 | int rc; |
| 146 | |
| 147 | /* For subsequent frames we run the error concealment |
| 148 | * functions on the backed up frame before we restore |
| 149 | * the backup */ |
| 150 | if (state->subsequent_lost_frame) { |
| 151 | rc = conceal_frame(state->frame_backup); |
| 152 | if (rc) |
| 153 | return rc; |
| 154 | } |
| 155 | |
| 156 | /* Restore the backed up frame and set flag in case |
| 157 | * we receive even more bad frames */ |
| 158 | memcpy(frame, state->frame_backup, GSM_FR_BYTES); |
| 159 | state->subsequent_lost_frame = true; |
| 160 | |
| 161 | return 0; |
| 162 | } |
Harald Welte | 750d831 | 2019-08-01 20:05:05 +0200 | [diff] [blame] | 163 | |
| 164 | /*********************************************************************** |
| 165 | * Integration with ECU core |
| 166 | ***********************************************************************/ |
| 167 | |
| 168 | static struct osmo_ecu_state *ecu_fr_init(void *ctx, enum osmo_ecu_codec codec) |
| 169 | { |
| 170 | struct osmo_ecu_state *st; |
| 171 | size_t size = sizeof(*st) + sizeof(struct osmo_ecu_fr_state); |
| 172 | |
| 173 | st = talloc_named_const(ctx, size, "ecu_state_FR"); |
| 174 | if (!st) |
| 175 | return NULL; |
| 176 | |
| 177 | memset(st, 0, size); |
| 178 | st->codec = codec; |
| 179 | |
| 180 | return st; |
| 181 | } |
| 182 | |
| 183 | static int ecu_fr_frame_in(struct osmo_ecu_state *st, bool bfi, const uint8_t *frame, |
| 184 | unsigned int frame_bytes) |
| 185 | { |
| 186 | struct osmo_ecu_fr_state *fr = (struct osmo_ecu_fr_state *) &st->data; |
| 187 | if (bfi) |
| 188 | return 0; |
| 189 | |
| 190 | osmo_ecu_fr_reset(fr, frame); |
| 191 | return 0; |
| 192 | } |
| 193 | |
| 194 | static int ecu_fr_frame_out(struct osmo_ecu_state *st, uint8_t *frame_out) |
| 195 | { |
| 196 | struct osmo_ecu_fr_state *fr = (struct osmo_ecu_fr_state *) &st->data; |
| 197 | |
| 198 | if (osmo_ecu_fr_conceal(fr, frame_out) == 0) |
| 199 | return GSM_FR_BYTES; |
| 200 | else |
| 201 | return -1; |
| 202 | } |
| 203 | |
| 204 | static const struct osmo_ecu_ops osmo_ecu_ops_fr = { |
| 205 | .init = ecu_fr_init, |
| 206 | .frame_in = ecu_fr_frame_in, |
| 207 | .frame_out = ecu_fr_frame_out, |
| 208 | }; |
| 209 | |
| 210 | static __attribute__((constructor)) void on_dso_load_ecu_fr(void) |
| 211 | { |
| 212 | osmo_ecu_register(&osmo_ecu_ops_fr, OSMO_ECU_CODEC_FR); |
| 213 | } |