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119 lines
2.9 KiB
119 lines
2.9 KiB
4 months ago
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/* K=9 r=1/2 Viterbi decoder for MMX
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* Copyright Feb 2004, Phil Karn, KA9Q
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* May be used under the terms of the GNU Lesser General Public License (LGPL)
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <memory.h>
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#include <mmintrin.h>
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#include "fec.h"
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typedef union { char c[256]; __m64 v[32];} decision_t;
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typedef union { unsigned char c[256]; __m64 v[32];} metric_t;
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unsigned char Mettab29_1[256][128] __attribute__ ((aligned(8)));
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unsigned char Mettab29_2[256][128] __attribute__ ((aligned(8)));
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static int Init = 0;
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/* State info for instance of Viterbi decoder
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* Don't change this without also changing references in mmxbfly29.s!
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*/
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struct v29 {
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metric_t metrics1; /* path metric buffer 1 */
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metric_t metrics2; /* path metric buffer 2 */
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decision_t *dp; /* Pointer to current decision */
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metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */
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decision_t *decisions; /* Beginning of decisions for block */
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};
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/* Create a new instance of a Viterbi decoder */
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void *create_viterbi29_mmx(int len){
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struct v29 *vp;
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if(Init == 0){
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int polys[2] = {V29POLYA,V29POLYB};
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set_viterbi29_polynomial_mmx(polys);
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}
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if((vp = (struct v29 *)malloc(sizeof(struct v29))) == NULL)
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return NULL;
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if((vp->decisions = (decision_t *)malloc((len+8)*sizeof(decision_t))) == NULL){
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free(vp);
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return NULL;
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}
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init_viterbi29(vp,0);
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return vp;
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}
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void set_viterbi29_polynomial_mmx(int polys[2]){
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int state;
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for(state=0;state < 128;state++){
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int symbol;
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for(symbol = 0;symbol < 256;symbol++){
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int sym;
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sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0);
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Mettab29_1[symbol][state] = (sym ? (255-symbol):symbol) / 16;
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sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0);
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Mettab29_2[symbol][state] = (sym ? (255-symbol):symbol) / 16;
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}
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}
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Init++;
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}
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/* Initialize Viterbi decoder for start of new frame */
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int init_viterbi29_mmx(void *p,int starting_state){
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struct v29 *vp = p;
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int i;
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if(p == NULL)
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return -1;
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for(i=0;i<256;i++)
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vp->metrics1.c[i] = 63;
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vp->old_metrics = &vp->metrics1;
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vp->new_metrics = &vp->metrics2;
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vp->dp = vp->decisions;
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vp->old_metrics->c[starting_state & 255] = 0; /* Bias known start state */
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return 0;
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}
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/* Viterbi chainback */
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int chainback_viterbi29_mmx(
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void *p,
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unsigned char *data, /* Decoded output data */
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unsigned int nbits, /* Number of data bits */
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unsigned int endstate){ /* Terminal encoder state */
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struct v29 *vp = (struct v29 *)p;
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decision_t *d;
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if(p == NULL)
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return -1;
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d = (decision_t *)vp->decisions;
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endstate &= 255;
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d += 8; /* Look past tail */
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while(nbits-- != 0){
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int k;
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k = d[nbits].c[endstate] & 1;
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data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
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}
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return 0;
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}
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/* Delete instance of a Viterbi decoder */
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void delete_viterbi29_mmx(void *p){
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struct v29 *vp = p;
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if(vp != NULL){
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free(vp->decisions);
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free(vp);
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}
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}
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