Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 1 | /* K=7 r=1/2 Viterbi decoder for MMX |
| 2 | * Copyright Feb 2004, Phil Karn, KA9Q |
| 3 | */ |
| 4 | #include <stdio.h> |
| 5 | #include <stdlib.h> |
| 6 | #include <memory.h> |
| 7 | #include <mmintrin.h> |
| 8 | #include "fec.h" |
| 9 | |
| 10 | typedef union { char c[64]; __m64 v[8];} decision_t; |
| 11 | typedef union { unsigned char c[64]; __m64 v[8];} metric_t; |
| 12 | |
| 13 | unsigned char Mettab27_1[256][32] __attribute__ ((aligned(16))); |
| 14 | unsigned char Mettab27_2[256][32] __attribute__ ((aligned(16))); |
| 15 | static int Init = 0; |
| 16 | |
| 17 | /* State info for instance of Viterbi decoder |
| 18 | * Don't change this without also changing references in mmxbfly27.s! |
| 19 | */ |
| 20 | struct v27 { |
| 21 | metric_t metrics1; /* path metric buffer 1 */ |
| 22 | metric_t metrics2; /* path metric buffer 2 */ |
| 23 | decision_t *dp; /* Pointer to current decision */ |
| 24 | metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */ |
| 25 | decision_t *decisions; /* Beginning of decisions for block */ |
| 26 | }; |
| 27 | |
| 28 | /* Initialize Viterbi decoder for start of new frame */ |
| 29 | int init_viterbi27_mmx(void *p,int starting_state){ |
| 30 | struct v27 *vp = (struct v27 *)p; |
| 31 | int i; |
| 32 | |
| 33 | if(p == NULL) |
| 34 | return -1; |
| 35 | for(i=0;i<64;i++) |
| 36 | vp->metrics1.c[i] = 63; |
| 37 | |
| 38 | vp->old_metrics = &vp->metrics1; |
| 39 | vp->new_metrics = &vp->metrics2; |
| 40 | vp->dp = vp->decisions; |
| 41 | vp->old_metrics->c[starting_state & 63] = 0; /* Bias known start state */ |
| 42 | return 0; |
| 43 | } |
| 44 | |
| 45 | void set_viterbi27_polynomial_mmx(int polys[2]){ |
| 46 | int state; |
| 47 | |
| 48 | for(state=0;state < 32;state++){ |
| 49 | int symbol; |
| 50 | for(symbol = 0;symbol < 256;symbol++){ |
| 51 | int sym; |
| 52 | |
| 53 | sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0); |
| 54 | Mettab27_1[symbol][state] = (sym ? (255-symbol):symbol) / 16; |
| 55 | |
| 56 | sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0); |
| 57 | Mettab27_2[symbol][state] = (sym ? (255-symbol):symbol) / 16; |
| 58 | } |
| 59 | } |
| 60 | Init++; |
| 61 | } |
| 62 | |
| 63 | |
| 64 | /* Create a new instance of a Viterbi decoder */ |
| 65 | void *create_viterbi27_mmx(int len){ |
| 66 | struct v27 *vp; |
| 67 | int polys[2] = { V27POLYA, V27POLYB }; |
| 68 | |
| 69 | if(Init == 0){ |
| 70 | set_viterbi27_polynomial_mmx(polys); |
| 71 | } |
| 72 | if((vp = (struct v27 *)malloc(sizeof(struct v27))) == NULL) |
| 73 | return NULL; |
| 74 | |
| 75 | if((vp->decisions = (decision_t *)malloc((len+6)*sizeof(decision_t))) == NULL){ |
| 76 | free(vp); |
| 77 | return NULL; |
| 78 | } |
| 79 | init_viterbi27_mmx(vp,0); |
| 80 | return vp; |
| 81 | } |
| 82 | |
| 83 | /* Viterbi chainback */ |
| 84 | int chainback_viterbi27_mmx( |
| 85 | void *p, |
| 86 | unsigned char *data, /* Decoded output data */ |
| 87 | unsigned int nbits, /* Number of data bits */ |
| 88 | unsigned int endstate){ /* Terminal encoder state */ |
| 89 | |
| 90 | struct v27 *vp = (struct v27 *)p; |
| 91 | decision_t *d; |
| 92 | |
| 93 | if(p == NULL) |
| 94 | return -1; |
| 95 | d = (decision_t *)vp->decisions; |
| 96 | endstate &= 63; |
| 97 | d += 6; /* Look past tail */ |
| 98 | while(nbits-- != 0){ |
| 99 | int k; |
| 100 | |
| 101 | k = d[nbits].c[endstate>>2] & 1; |
| 102 | data[nbits>>3] = endstate = (endstate >> 1) | (k << 7); |
| 103 | } |
| 104 | return 0; |
| 105 | } |
| 106 | |
| 107 | /* Delete instance of a Viterbi decoder */ |
| 108 | void delete_viterbi27_mmx(void *p){ |
| 109 | struct v27 *vp = p; |
| 110 | |
| 111 | if(vp != NULL){ |
| 112 | free(vp->decisions); |
| 113 | free(vp); |
| 114 | } |
| 115 | } |