Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 1 | /* K=9 r=1/2 Viterbi decoder for MMX |
| 2 | * Copyright Feb 2004, Phil Karn, KA9Q |
| 3 | * May be used under the terms of the GNU Lesser General Public License (LGPL) |
| 4 | */ |
| 5 | #include <stdio.h> |
| 6 | #include <stdlib.h> |
| 7 | #include <memory.h> |
| 8 | #include <mmintrin.h> |
| 9 | #include "fec.h" |
| 10 | |
| 11 | typedef union { char c[256]; __m64 v[32];} decision_t; |
| 12 | typedef union { unsigned char c[256]; __m64 v[32];} metric_t; |
| 13 | |
| 14 | unsigned char Mettab29_1[256][128] __attribute__ ((aligned(8))); |
| 15 | unsigned char Mettab29_2[256][128] __attribute__ ((aligned(8))); |
| 16 | static int Init = 0; |
| 17 | |
| 18 | /* State info for instance of Viterbi decoder |
| 19 | * Don't change this without also changing references in mmxbfly29.s! |
| 20 | */ |
| 21 | struct v29 { |
| 22 | metric_t metrics1; /* path metric buffer 1 */ |
| 23 | metric_t metrics2; /* path metric buffer 2 */ |
| 24 | decision_t *dp; /* Pointer to current decision */ |
| 25 | metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */ |
| 26 | decision_t *decisions; /* Beginning of decisions for block */ |
| 27 | }; |
| 28 | |
| 29 | /* Create a new instance of a Viterbi decoder */ |
| 30 | void *create_viterbi29_mmx(int len){ |
| 31 | struct v29 *vp; |
| 32 | |
| 33 | if(Init == 0){ |
| 34 | int polys[2] = {V29POLYA,V29POLYB}; |
| 35 | |
| 36 | set_viterbi29_polynomial_mmx(polys); |
| 37 | } |
| 38 | if((vp = (struct v29 *)malloc(sizeof(struct v29))) == NULL) |
| 39 | return NULL; |
| 40 | |
| 41 | if((vp->decisions = (decision_t *)malloc((len+8)*sizeof(decision_t))) == NULL){ |
| 42 | free(vp); |
| 43 | return NULL; |
| 44 | } |
| 45 | init_viterbi29(vp,0); |
| 46 | return vp; |
| 47 | } |
| 48 | |
| 49 | void set_viterbi29_polynomial_mmx(int polys[2]){ |
| 50 | int state; |
| 51 | |
| 52 | for(state=0;state < 128;state++){ |
| 53 | int symbol; |
| 54 | |
| 55 | for(symbol = 0;symbol < 256;symbol++){ |
| 56 | int sym; |
| 57 | |
| 58 | sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0); |
| 59 | Mettab29_1[symbol][state] = (sym ? (255-symbol):symbol) / 16; |
| 60 | |
| 61 | sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0); |
| 62 | Mettab29_2[symbol][state] = (sym ? (255-symbol):symbol) / 16; |
| 63 | } |
| 64 | } |
| 65 | Init++; |
| 66 | } |
| 67 | |
| 68 | /* Initialize Viterbi decoder for start of new frame */ |
| 69 | int init_viterbi29_mmx(void *p,int starting_state){ |
| 70 | struct v29 *vp = p; |
| 71 | int i; |
| 72 | |
| 73 | if(p == NULL) |
| 74 | return -1; |
| 75 | for(i=0;i<256;i++) |
| 76 | vp->metrics1.c[i] = 63; |
| 77 | |
| 78 | vp->old_metrics = &vp->metrics1; |
| 79 | vp->new_metrics = &vp->metrics2; |
| 80 | vp->dp = vp->decisions; |
| 81 | vp->old_metrics->c[starting_state & 255] = 0; /* Bias known start state */ |
| 82 | return 0; |
| 83 | } |
| 84 | |
| 85 | /* Viterbi chainback */ |
| 86 | int chainback_viterbi29_mmx( |
| 87 | void *p, |
| 88 | unsigned char *data, /* Decoded output data */ |
| 89 | unsigned int nbits, /* Number of data bits */ |
| 90 | unsigned int endstate){ /* Terminal encoder state */ |
| 91 | |
| 92 | struct v29 *vp = (struct v29 *)p; |
| 93 | decision_t *d; |
| 94 | |
| 95 | if(p == NULL) |
| 96 | return -1; |
| 97 | |
| 98 | d = (decision_t *)vp->decisions; |
| 99 | endstate &= 255; |
| 100 | d += 8; /* Look past tail */ |
| 101 | while(nbits-- != 0){ |
| 102 | int k; |
| 103 | |
| 104 | k = d[nbits].c[endstate] & 1; |
| 105 | data[nbits>>3] = endstate = (endstate >> 1) | (k << 7); |
| 106 | } |
| 107 | return 0; |
| 108 | } |
| 109 | |
| 110 | /* Delete instance of a Viterbi decoder */ |
| 111 | void delete_viterbi29_mmx(void *p){ |
| 112 | struct v29 *vp = p; |
| 113 | |
| 114 | if(vp != NULL){ |
| 115 | free(vp->decisions); |
| 116 | free(vp); |
| 117 | } |
| 118 | } |