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adjusted fir_hook() to use the new history buffer

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This commit is contained in:
Steffen Vogel 2015-04-01 13:27:10 +02:00
parent 9f4dd78ab3
commit e1d63db91b
3 changed files with 26 additions and 28 deletions
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2
server/include/hooks.h
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@ -65,7 +65,7 @@ int hook_tofixed(struct msg *m, struct path *p);
/** Example hook: add timestamp to message. */
int hook_ts(struct msg *m, struct path *p);
#define HOOK_TS_INDEX -1 // last message
#define HOOK_TS_INDEX -1 /* last message */
/** Example hook: Finite-Impulse-Response (FIR) filter. */
int hook_fir(struct msg *m, struct path *p);

10
server/include/utils.h
View file

@ -60,6 +60,16 @@
b = tmp; \
} while(0)
/* Return the bigger value */
#define MAX(a, b) ({ __typeof__ (a) _a = (a); \
__typeof__ (b) _b = (b); \
_a > _b ? _a : _b; })
/* Return the smaller value */
#define MIN(a, b) ({ __typeof__ (a) _a = (a); \
__typeof__ (b) _b = (b); \
_a < _b ? _a : _b; })
/* Forward declarations */
struct settings;
struct timespec;

42
server/src/hooks.c
View file

@ -13,7 +13,6 @@
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <pthread.h>
#include <time.h>
#include "msg.h"
@ -102,39 +101,28 @@ int hook_ts(struct msg *m, struct path *p)
return 0;
}
/** Simple FIR-LP: F_s = 1kHz, F_pass = 100 Hz, F_block = 300
* Tip: Use MATLAB's filter design tool and export coefficients
* with the integrated C-Header export */
static const double hook_fir_coeffs[] = { -0.003658148158728, -0.008882653268281, 0.008001024183003,
0.08090485991761, 0.2035239551043, 0.3040703593515,
0.3040703593515, 0.2035239551043, 0.08090485991761,
0.008001024183003, -0.008882653268281,-0.003658148158728 };
/** @todo: test */
int hook_fir(struct msg *m, struct path *p)
{
static pthread_key_t pkey;
float *history = pthread_getspecific(pkey);
/** Simple FIR-LP: F_s = 1kHz, F_pass = 100 Hz, F_block = 300
* Tip: Use MATLAB's filter design tool and export coefficients
* with the integrated C-Header export */
static const double coeffs[] = {
-0.003658148158728, -0.008882653268281, 0.008001024183003,
0.08090485991761, 0.2035239551043, 0.3040703593515,
0.3040703593515, 0.2035239551043, 0.08090485991761,
0.008001024183003, -0.008882653268281,-0.003658148158728 };
/** Length of impulse response */
int len = ARRAY_LEN(hook_fir_coeffs);
/** Current index in circular history buffer */
int cur = m->sequence % len;
/* Accumulator */
double sum = 0;
/** Trim FIR length to length of history buffer */
int len = MIN(ARRAY_LEN(coeffs), POOL_SIZE);
for (int i=0; i<len; i++) {
struct msg *old = &p->history[(POOL_SIZE+p->received-i) % POOL_SIZE];
/* Create thread local storage for circular history buffer */
if (!history) {
history = alloc(len * sizeof(float));
pthread_key_create(&pkey, free);
pthread_setspecific(pkey, history);
sum += coeffs[i] * old->data[HOOK_FIR_INDEX].f;
}
/* Update circular buffer */
history[cur] = m->data[HOOK_FIR_INDEX].f;
for (int i=0; i<len; i++)
sum += hook_fir_coeffs[(cur+len-i)%len] * history[(cur+i)%len];
m->data[HOOK_FIR_INDEX].f = sum;