common code: Sample rate conversion now supports any rate above 8000 Hz

src/anetz/anetz.c

@@ -468,7 +468,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 		return;
 
 	if (anetz->dsp_mode == DSP_MODE_AUDIO) {
-		int16_t up[count * anetz->sender.srstate.factor];
+		int16_t up[(int)((double)count * anetz->sender.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&anetz->sender.srstate, samples, count, up);
 		jitter_save(&anetz->sender.audio, up, count);
 	}

src/bnetz/bnetz.c

@@ -862,7 +862,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 		return;
 
 	if (bnetz->dsp_mode == DSP_MODE_AUDIO) {
-		int16_t up[count * bnetz->sender.srstate.factor];
+		int16_t up[(int)((double)count * bnetz->sender.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&bnetz->sender.srstate, samples, count, up);
 		jitter_save(&bnetz->sender.audio, up, count);
 	}

src/common/call.c

@@ -524,18 +524,18 @@ int process_call(void)
 		return 0;
 	}
 	if (count < call.latspl) {
-		int16_t up[count];
+		int16_t up[count + 10];
 		count = call.latspl - count;
 		switch(call.state) {
 		case CALL_ALERTING:
-			count = count / call.srstate.factor;
+			count = (int)((double)count / call.srstate.factor + 0.5);
 			get_call_patterns(samples, count, PATTERN_RINGBACK);
 			count = samplerate_upsample(&call.srstate, samples, count, up);
 			/* prevent click after hangup */
 			jitter_clear(&call.audio);
 			break;
 		case CALL_DISCONNECTED:
-			count = count / call.srstate.factor;
+			count = (int)((double)count / call.srstate.factor + 0.5);
 			get_call_patterns(samples, count, cause2pattern(call.disc_cause));
 			count = samplerate_upsample(&call.srstate, samples, count, up);
 			/* prevent click after hangup */
@@ -766,7 +766,7 @@ void call_tx_audio(int callref, int16_t *samples, int count)
 
 	/* save audio from transceiver to jitter buffer */
 	if (call.sound) {
-		int16_t up[count * call.srstate.factor];
+		int16_t up[(int)((double)count * call.srstate.factor + 0.5) + 10];
 		count = samplerate_upsample(&call.srstate, samples, count, up);
 		jitter_save(&call.audio, up, count);
 	}

src/common/samplerate.c

@@ -21,21 +21,21 @@
 #include <stdint.h>
 #include <errno.h>
 #include <string.h>
+#include <stdlib.h>
 #include "samplerate.h"
 
-/* generally use filter, but disable for test using quick and dirty replacement */
-#define USE_FILTER
-
 /* NOTE: This is quick and dirtry. */
 
-int init_samplerate(samplerate_t *state, int samplerate)
+int init_samplerate(samplerate_t *state, double samplerate)
 {
+#if 0
 	if ((samplerate % 8000)) {
 		fprintf(stderr, "Sample rate must be a muliple of 8000 to support MNCC socket interface, aborting!\n");
 		return -EINVAL;
 	}
+#endif
 	memset(state, 0, sizeof(*state));
-	state->factor = samplerate / 8000;
+	state->factor = samplerate / 8000.0;
 
 	biquad_init(&state->up.bq, 4000.0, samplerate);
 	biquad_init(&state->down.bq, 4000.0, samplerate);
@@ -46,10 +46,9 @@ int init_samplerate(samplerate_t *state, int samplerate)
 /* convert input sample rate to 8000 Hz */
 int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
 {
-#ifdef USE_FILTER
-	int output_num, i, j;
-	int factor = state->factor;
-	double spl[input_num];
+	int output_num, i;
+	double factor = state->factor, step;
+	double spl[input_num + 10]; /* add some safety */
 	int32_t value;
 
 	/* convert samples to double */
@@ -58,62 +57,42 @@ int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, in
 
 	/* filter down */
 	biquad_process(&state->down.bq, spl, input_num, 1);
-	output_num = input_num / factor;
+	output_num = (int)((double)input_num / factor);
 
 	/* resample filtered result */
-	for (i = 0, j = 0; i < output_num; i++, j += factor) {
-		value = spl[j] * 32768.0;
+	for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor) {
+		value = spl[(int)step] * 32768.0;
 		if (value < -32768)
 			value = -32768;
 		else if (value > 32767)
 			value = 32767;
 		*output++ = value;
 	}
-
-	return output_num;
-#else
-	int output_num = 0, i;
-	double sum;
-	int factor, sum_count;
-
-//memcpy(output, input, input_num*2);
-//return input_num;
-	sum = state->down.sum;
-	sum_count = state->down.sum_count;
-	factor = state->factor;
-
-	for (i = 0; i < input_num; i++) {
-		sum += *input++;
-		sum_count++;
-		if (sum_count == factor) {
-			*output++ = sum / (double)sum_count;
-			output_num++;
-			sum = 0;
-			sum_count = 0;
-		}
+	if ((int)(step - factor) >= input_num) {
+		fprintf(stderr, "Error: input_num is %d, so step should be close to 0.5 below that, but it is %.4f. Please fix!\n", input_num, step);
+		abort();
 	}
 
-	state->down.sum = sum;
-	state->down.sum_count = sum_count;
-
 	return output_num;
-#endif
 }
 
 /* convert 8000 Hz sample rate to output sample rate */
 int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output)
 {
-#ifdef USE_FILTER
 	int output_num, i;
-	int factor = state->factor;
-	double spl[input_num * factor];
+	double factor = 1.0 / state->factor, step;
+	double spl[(int)((double)input_num / factor + 0.5) + 10]; /* add some fafety */
 	int32_t value;
 
-	output_num = input_num * factor;
+	output_num = (int)((double)input_num / factor + 0.5);
 
 	/* resample input */
-	for (i = 0; i < output_num; i++)
-		spl[i] = input[i / factor] / 32768.0;
+	for (i = 0, step = 0.5 / (double)output_num; i < output_num; i++, step += factor)
+		spl[i] = input[(int)step] / 32768.0;
+	if ((int)(step - factor) >= input_num) {
+		fprintf(stderr, "Error: input_num is %d, so step should be close to 0.5 below that, but it is %.4f. Please fix!\n", input_num, step);
+		abort();
+	}
 
 	/* filter up */
 	biquad_process(&state->up.bq, spl, output_num, 1);
@@ -129,31 +108,5 @@ int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int1
 	}
 
 	return output_num;
-#else
-	int output_num = 0, i, j;
-	double last_sample, sample, slope;
-	int factor;
-
-	last_sample = state->up.last_sample;
-	factor = state->factor;
-
-	for (i = 0; i < input_num; i++) {
-		sample = *input++;
-		slope = (double)(sample - last_sample) / (double)factor;
-//int jolly = (int)last_sample;
-		for (j = 0; j < factor; j++) {
-//			if (last_sample > 32767 || last_sample < -32767)
-//				printf("%.5f sample=%.0f, last_sample=%d, slope=%.5f\n", last_sample, sample, jolly, slope);
-			*output++ = last_sample;
-			output_num++;
-			last_sample += slope;
-		}
-		last_sample = sample;
-	}
-
-	state->up.last_sample = last_sample;
-
-	return output_num;
-#endif
 }
 

src/common/samplerate.h

@@ -1,10 +1,10 @@
 #include "filter.h"
 
 typedef struct samplerate {
-	int factor;
+	double factor;
 	struct {
 		double sum;
-		int sum_count;
+		double sum_count;
 		biquad_low_pass_t bq;
 	} down;
 	struct {
@@ -13,6 +13,6 @@ typedef struct samplerate {
 	} up;
 } samplerate_t;
 
-int init_samplerate(samplerate_t *state, int samplerate);
+int init_samplerate(samplerate_t *state, double samplerate);
 int samplerate_downsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output);
 int samplerate_upsample(samplerate_t *state, int16_t *input, int input_num, int16_t *output);

src/nmt/nmt.c

@@ -1450,7 +1450,7 @@ void call_rx_audio(int callref, int16_t *samples, int count)
 		return;
 
 	if (nmt->dsp_mode == DSP_MODE_AUDIO || nmt->dsp_mode == DSP_MODE_DTMF) {
-		int16_t up[count * nmt->sender.srstate.factor];
+		int16_t up[(int)((double)count * nmt->sender.srstate.factor + 0.5) + 10];
 		if (nmt->compander)
 			compress_audio(&nmt->cstate, samples, count);
 		count = samplerate_upsample(&nmt->sender.srstate, samples, count, up);