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C-Netz: Minor fixes to pulse shaping code

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pull/1/head
Andreas Eversberg 1 year ago
parent 3e5326f891
commit 0ebd53ac69
1 changed files with 18 additions and 20 deletions
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  1. 38
      src/cnetz/dsp.c

38
src/cnetz/dsp.c
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@ -75,8 +75,6 @@ const char *cnetz_dsp_mode_name(enum dsp_mode mode)
return invalid;
}
static sample_t ramp_up[256], ramp_down[256];
void dsp_init(void)
{
}
@ -88,15 +86,15 @@ static void dsp_init_ramp(cnetz_t *cnetz)
PDEBUG(DDSP, DEBUG_DEBUG, "Generating smooth ramp table.\n");
for (i = 0; i < 256; i++) {
c = cos((double)i / 256.0 * PI);
/* use square-root of cosine ramp. tests showed that phones are more
* happy with that. */
* happy with that. (This is not correct pulse shaping!) */
c = cos((double)i / 256.0 * PI);
if (c < 0)
c = -sqrt(-c);
else
c = sqrt(c);
ramp_down[i] = c * (double)cnetz->fsk_deviation;
ramp_up[i] = -ramp_down[i];
cnetz->fsk_ramp_down[i] = c * (double)cnetz->fsk_deviation;
cnetz->fsk_ramp_up[i] = -cnetz->fsk_ramp_down[i];
}
}
@ -331,14 +329,14 @@ static int fsk_block_encode(cnetz_t *cnetz, const char *bits, int ogk)
if (bits[i] == '1') {
/* ramp up from 0 */
do {
*spl++ = ramp_up[(uint8_t)phase] / 2 + deviation / 2;
*spl++ = cnetz->fsk_ramp_up[(uint8_t)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down from 0 */
do {
*spl++ = ramp_down[(uint8_t)phase] / 2 - deviation / 2;
*spl++ = cnetz->fsk_ramp_down[(uint8_t)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -355,7 +353,7 @@ static int fsk_block_encode(cnetz_t *cnetz, const char *bits, int ogk)
} else {
/* ramp down */
do {
*spl++ = ramp_down[(uint8_t)phase];
*spl++ = cnetz->fsk_ramp_down[(uint8_t)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -365,7 +363,7 @@ static int fsk_block_encode(cnetz_t *cnetz, const char *bits, int ogk)
if (bits[i] == '1') {
/* ramp up */
do {
*spl++ = ramp_up[(uint8_t)phase];
*spl++ = cnetz->fsk_ramp_up[(uint8_t)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -385,14 +383,14 @@ static int fsk_block_encode(cnetz_t *cnetz, const char *bits, int ogk)
if (last == '0') {
/* ramp up to 0 */
do {
*spl++ = ramp_up[(uint8_t)phase] / 2 - deviation / 2;
*spl++ = cnetz->fsk_ramp_up[(uint8_t)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down to 0 */
do {
*spl++ = ramp_down[(uint8_t)phase] / 2 + deviation / 2;
*spl++ = cnetz->fsk_ramp_down[(uint8_t)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -481,14 +479,14 @@ static int fsk_distributed_encode(cnetz_t *cnetz, const char *bits)
if (bits[i * 4 + j] == '1') {
/* ramp up from 0 */
do {
*spl++ = ramp_up[(uint8_t)phase] / 2 + deviation / 2;
*spl++ = cnetz->fsk_ramp_up[(uint8_t)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down from 0 */
do {
*spl++ = ramp_down[(uint8_t)phase] / 2 - deviation / 2;
*spl++ = cnetz->fsk_ramp_down[(uint8_t)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -505,7 +503,7 @@ static int fsk_distributed_encode(cnetz_t *cnetz, const char *bits)
} else {
/* ramp down */
do {
*spl++ = ramp_down[(uint8_t)phase];
*spl++ = cnetz->fsk_ramp_down[(uint8_t)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -515,7 +513,7 @@ static int fsk_distributed_encode(cnetz_t *cnetz, const char *bits)
if (bits[i * 4 + j] == '1') {
/* ramp up */
do {
*spl++ = ramp_up[(uint8_t)phase];
*spl++ = cnetz->fsk_ramp_up[(uint8_t)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -535,14 +533,14 @@ static int fsk_distributed_encode(cnetz_t *cnetz, const char *bits)
if (last == '0') {
/* ramp up to 0 */
do {
*spl++ = ramp_up[(uint8_t)phase] / 2 - deviation / 2;
*spl++ = cnetz->fsk_ramp_up[(uint8_t)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down to 0 */
do {
*spl++ = ramp_down[(uint8_t)phase] / 2 + deviation / 2;
*spl++ = cnetz->fsk_ramp_down[(uint8_t)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
@ -755,7 +753,7 @@ again:
/* ramp before speech */
for (j = 0; j < begin; j++) {
/* ramp up from 0 to speech level */
speech_buffer[j] = speech_buffer[begin] * (ramp_up[j * 256 / begin] / cnetz->fsk_deviation / 2.0 + 0.5);
speech_buffer[j] = speech_buffer[begin] * (cnetz->fsk_ramp_up[j * 256 / begin] / cnetz->fsk_deviation / 2.0 + 0.5);
}
speech_length += begin; /* add one bit duration before speech*/
/* ramp after speech */
@ -766,7 +764,7 @@ again:
speech_length = end; /* shorten 'speech_length', if greater than 'end' */
for (j = 0; j < begin; j++) {
/* ramp down from speech level to 0 */
speech_buffer[end + j] = speech_buffer[end - 1] * (ramp_down[j * 256 / begin] / cnetz->fsk_deviation / 2.0 + 0.5);
speech_buffer[end + j] = speech_buffer[end - 1] * (cnetz->fsk_ramp_down[j * 256 / begin] / cnetz->fsk_deviation / 2.0 + 0.5);
}
speech_length += begin; /* add one bit duration after speech */
speech_pos = 0;

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