xref: /aosp_15_r20/external/liblc3/src/plc.c (revision 49fe348c0058011ee60b6957cdd9d52742df84bc)
1*49fe348cSAndroid Build Coastguard Worker /******************************************************************************
2*49fe348cSAndroid Build Coastguard Worker  *
3*49fe348cSAndroid Build Coastguard Worker  *  Copyright 2022 Google LLC
4*49fe348cSAndroid Build Coastguard Worker  *
5*49fe348cSAndroid Build Coastguard Worker  *  Licensed under the Apache License, Version 2.0 (the "License");
6*49fe348cSAndroid Build Coastguard Worker  *  you may not use this file except in compliance with the License.
7*49fe348cSAndroid Build Coastguard Worker  *  You may obtain a copy of the License at:
8*49fe348cSAndroid Build Coastguard Worker  *
9*49fe348cSAndroid Build Coastguard Worker  *  http://www.apache.org/licenses/LICENSE-2.0
10*49fe348cSAndroid Build Coastguard Worker  *
11*49fe348cSAndroid Build Coastguard Worker  *  Unless required by applicable law or agreed to in writing, software
12*49fe348cSAndroid Build Coastguard Worker  *  distributed under the License is distributed on an "AS IS" BASIS,
13*49fe348cSAndroid Build Coastguard Worker  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14*49fe348cSAndroid Build Coastguard Worker  *  See the License for the specific language governing permissions and
15*49fe348cSAndroid Build Coastguard Worker  *  limitations under the License.
16*49fe348cSAndroid Build Coastguard Worker  *
17*49fe348cSAndroid Build Coastguard Worker  ******************************************************************************/
18*49fe348cSAndroid Build Coastguard Worker 
19*49fe348cSAndroid Build Coastguard Worker #include "plc.h"
20*49fe348cSAndroid Build Coastguard Worker #include "tables.h"
21*49fe348cSAndroid Build Coastguard Worker 
22*49fe348cSAndroid Build Coastguard Worker 
23*49fe348cSAndroid Build Coastguard Worker /**
24*49fe348cSAndroid Build Coastguard Worker  * Reset Packet Loss Concealment state
25*49fe348cSAndroid Build Coastguard Worker  */
lc3_plc_reset(struct lc3_plc_state * plc)26*49fe348cSAndroid Build Coastguard Worker void lc3_plc_reset(struct lc3_plc_state *plc)
27*49fe348cSAndroid Build Coastguard Worker {
28*49fe348cSAndroid Build Coastguard Worker     plc->seed = 24607;
29*49fe348cSAndroid Build Coastguard Worker     lc3_plc_suspend(plc);
30*49fe348cSAndroid Build Coastguard Worker }
31*49fe348cSAndroid Build Coastguard Worker 
32*49fe348cSAndroid Build Coastguard Worker /**
33*49fe348cSAndroid Build Coastguard Worker  * Suspend PLC execution (Good frame received)
34*49fe348cSAndroid Build Coastguard Worker  */
lc3_plc_suspend(struct lc3_plc_state * plc)35*49fe348cSAndroid Build Coastguard Worker void lc3_plc_suspend(struct lc3_plc_state *plc)
36*49fe348cSAndroid Build Coastguard Worker {
37*49fe348cSAndroid Build Coastguard Worker     plc->count = 1;
38*49fe348cSAndroid Build Coastguard Worker     plc->alpha = 1.0f;
39*49fe348cSAndroid Build Coastguard Worker }
40*49fe348cSAndroid Build Coastguard Worker 
41*49fe348cSAndroid Build Coastguard Worker /**
42*49fe348cSAndroid Build Coastguard Worker  * Synthesis of a PLC frame
43*49fe348cSAndroid Build Coastguard Worker  */
lc3_plc_synthesize(enum lc3_dt dt,enum lc3_srate sr,struct lc3_plc_state * plc,const float * x,float * y)44*49fe348cSAndroid Build Coastguard Worker void lc3_plc_synthesize(enum lc3_dt dt, enum lc3_srate sr,
45*49fe348cSAndroid Build Coastguard Worker     struct lc3_plc_state *plc, const float *x, float *y)
46*49fe348cSAndroid Build Coastguard Worker {
47*49fe348cSAndroid Build Coastguard Worker     uint16_t seed = plc->seed;
48*49fe348cSAndroid Build Coastguard Worker     float alpha = plc->alpha;
49*49fe348cSAndroid Build Coastguard Worker     int ne = lc3_ne(dt, sr);
50*49fe348cSAndroid Build Coastguard Worker 
51*49fe348cSAndroid Build Coastguard Worker     alpha *= (plc->count < 4 ? 1.0f :
52*49fe348cSAndroid Build Coastguard Worker               plc->count < 8 ? 0.9f : 0.85f);
53*49fe348cSAndroid Build Coastguard Worker 
54*49fe348cSAndroid Build Coastguard Worker     for (int i = 0; i < ne; i++) {
55*49fe348cSAndroid Build Coastguard Worker         seed = (16831 + seed * 12821) & 0xffff;
56*49fe348cSAndroid Build Coastguard Worker         y[i] = alpha * (seed & 0x8000 ? -x[i] : x[i]);
57*49fe348cSAndroid Build Coastguard Worker     }
58*49fe348cSAndroid Build Coastguard Worker 
59*49fe348cSAndroid Build Coastguard Worker     plc->seed = seed;
60*49fe348cSAndroid Build Coastguard Worker     plc->alpha = alpha;
61*49fe348cSAndroid Build Coastguard Worker     plc->count++;
62*49fe348cSAndroid Build Coastguard Worker }
63