Allow data rates greater than 9600 baud.

	modified:   audio.h
	modified:   demod.c
	modified:   direwolf.c
	modified:   gen_packets.c
	modified:   gen_tone.c

Author: wb2osz

audio.h

@@ -278,8 +278,12 @@ struct audio_s {
 					/* 44100 works a little better than 22050. */
 					/* If you have a reasonable machine, use the highest rate. */
 #define MIN_SAMPLES_PER_SEC	8000
-#define MAX_SAMPLES_PER_SEC	48000	/* Formerly 44100. */
-					/* Software defined radio often uses 48000. */
+//#define MAX_SAMPLES_PER_SEC	48000	/* Originally 44100.  Later increased because */
+					/* Software Defined Radio often uses 48000. */
+
+#define MAX_SAMPLES_PER_SEC	192000	/* The cheap USB-audio adapters (e.g. CM108) can handle 44100 and 48000. */
+					/* The "soundcard" in my desktop PC can do 96kHz or even 192kHz. */
+					/* We will probably need to increase the sample rate to go much above 9600 baud. */
 
 #define DEFAULT_BITS_PER_SAMPLE	16
 
@@ -301,12 +305,12 @@ struct audio_s {
 #define DEFAULT_BAUD		1200
 
 /* Used for sanity checking in config file and command line options. */
-/* 9600 is known to work.  */
-/* TODO: Is 19200 possible with a soundcard at 44100 samples/sec? */
+/* 9600 baud is known to work.  */
+/* TODO: Is 19200 possible with a soundcard at 44100 samples/sec or do we need a higher sample rate? */
 
 #define MIN_BAUD		100
-#define MAX_BAUD		10000
-
+//#define MAX_BAUD		10000
+#define MAX_BAUD		40000		// Anyone want to try 38.4 k baud?
 
 /*
  * Typical transmit timings for VHF.

demod.c

@@ -562,6 +562,35 @@ int demod_init (struct audio_s *pa)
 	        save_audio_config_p->achan[chan].num_slicers = MAX_SLICERS;
      	      }
 
+
+	      /* We need a minimum number of audio samples per bit time for good performance. */
+	      /* Easier to check here because demod_9600_init might have an adjusted sample rate. */
+
+	      float ratio = (float)(save_audio_config_p->adev[ACHAN2ADEV(chan)].samples_per_sec)
+							/ (float)(save_audio_config_p->achan[chan].baud);
+
+	      text_color_set(DW_COLOR_INFO);
+	      dw_printf ("The ratio of audio samples per sec (%d) to data rate in baud (%d) is %.1f\n",
+				save_audio_config_p->adev[ACHAN2ADEV(chan)].samples_per_sec,
+				save_audio_config_p->achan[chan].baud,
+				ratio);
+	      if (ratio < 3) {
+	        text_color_set(DW_COLOR_ERROR);
+	        dw_printf ("There is little hope of success with such a low ratio.  Use a higher sample rate.\n");
+	      }
+	      else if (ratio < 5) {
+	        dw_printf ("This is on the low side for best performance.  Can you use a higher sample rate?\n");
+	      }
+	      else if (ratio < 6) {
+	        dw_printf ("Increasing the sample rate should improve decoder performance.\n");
+	      }
+	      else if (ratio > 15) {
+	        dw_printf ("Sample rate is more than adequate.  You might lower it if CPU load is a concern.\n");
+	      }
+	      else {
+	        dw_printf ("This is a suitable ratio for good performance.\n");
+	      }
+
 	      demod_9600_init (UPSAMPLE * save_audio_config_p->adev[ACHAN2ADEV(chan)].samples_per_sec, save_audio_config_p->achan[chan].baud, D);
 
 	      if (strchr(save_audio_config_p->achan[chan].profiles, '+') != NULL) {

direwolf.c

@@ -369,9 +369,9 @@ int main (int argc, char *argv[])
           case 'B':				/* -B baud rate and modem properties. */
 
 	    B_opt = atoi(optarg);
-            if (B_opt < 100 || B_opt > 10000) {
+            if (B_opt < MIN_BAUD || B_opt > MAX_BAUD) {
 	      text_color_set(DW_COLOR_ERROR);
-              dw_printf ("Use a more reasonable data baud rate in range of 100 - 10000.\n");
+              dw_printf ("Use a more reasonable data baud rate in range of %d - %d.\n", MIN_BAUD, MAX_BAUD);
               exit (EXIT_FAILURE);
             }
             break;

gen_packets.c

@@ -196,9 +196,9 @@ int main(int argc, char **argv)
               modem.achan[0].baud = atoi(optarg);
               text_color_set(DW_COLOR_INFO); 
               dw_printf ("Data rate set to %d bits / second.\n", modem.achan[0].baud);
-              if (modem.achan[0].baud < 100 || modem.achan[0].baud > 10000) {
+              if (modem.achan[0].baud < MIN_BAUD || modem.achan[0].baud > MAX_BAUD) {
                 text_color_set(DW_COLOR_ERROR); 
-                dw_printf ("Use a more reasonable bit rate in range of 100 - 10000.\n");
+                dw_printf ("Use a more reasonable bit rate in range of %d - %d.\n", MIN_BAUD, MAX_BAUD);
                 exit (EXIT_FAILURE);
               }
               break;
@@ -208,29 +208,30 @@ int main(int argc, char **argv)
 						/*    1200 implies 1200/2200 AFSK. */
 						/*    9600 implies scrambled. */
 
+						/* If you want something else, specify -B first */
+						/* then anything to override these defaults. */
+
               modem.achan[0].baud = atoi(optarg);
               text_color_set(DW_COLOR_INFO); 
               dw_printf ("Data rate set to %d bits / second.\n", modem.achan[0].baud);
-              if (modem.achan[0].baud < 100 || modem.achan[0].baud > 10000) {
+              if (modem.achan[0].baud < MIN_BAUD || modem.achan[0].baud > MAX_BAUD) {
                 text_color_set(DW_COLOR_ERROR); 
-                dw_printf ("Use a more reasonable bit rate in range of 100 - 10000.\n");
+                dw_printf ("Use a more reasonable bit rate in range of %d - %d.\n", MIN_BAUD, MAX_BAUD);
                 exit (EXIT_FAILURE);
               }
 
-	      switch (modem.achan[0].baud) {
-	        case 300:
+	      if (modem.achan[0].baud < 600) {
                   modem.achan[0].mark_freq = 1600;
                   modem.achan[0].space_freq = 1800;
-	          break;
-	        case 1200:
+	      }
+	      else if (modem.achan[0].baud <= 2400) {
                   modem.achan[0].mark_freq = 1200;
                   modem.achan[0].space_freq = 2200;
-	          break;
-	        case 9600:
+	      }
+	      else {
                   modem.achan[0].modem_type = MODEM_SCRAMBLE;
                   text_color_set(DW_COLOR_INFO); 
                   dw_printf ("Using scrambled baseband signal rather than AFSK.\n");
-	          break;
 	      }
               break;
 

gen_tone.c

@@ -210,10 +210,18 @@ int gen_tone_init (struct audio_s *audio_config_p, int amp)
 	  a = ((double)(j) / 256.0) * (2 * M_PI);
 	  s = (int) (sin(a) * 32767 * amp / 100.0);
 
-	  /* 16 bit sound sample is in range of -32768 .. +32767. */
-	  
-	  assert (s >= -32768 && s <= 32767);
+	  /* 16 bit sound sample must fit in range of -32768 .. +32767. */
 
+	  if (s < -32768) {
+	    text_color_set(DW_COLOR_ERROR);
+	    dw_printf ("gen_tone_init: Excessive amplitude is being clipped.\n");
+	    s = -32768;
+	  }
+	  else if (s > 32767) {
+	    text_color_set(DW_COLOR_ERROR);
+	    dw_printf ("gen_tone_init: Excessive amplitude is being clipped.\n");
+	    s = 32767;
+	  }
 	  sine_table[j] = s;
         }
 
@@ -235,7 +243,8 @@ int gen_tone_init (struct audio_s *audio_config_p, int amp)
 	    /* These numbers were by trial and error.  Need more investigation here. */
 
 	    float filter_len_bits =  88 * 9600.0 / (44100.0 * 2.0);
-						/* Filter length in number of data bits. */	
+						/* Filter length in number of data bits. */
+						/* Currently 9.58 */
 
 	    float lpf_baud = 0.8;		/* Lowpass cutoff freq as fraction of baud rate */
 
@@ -250,10 +259,15 @@ int gen_tone_init (struct audio_s *audio_config_p, int amp)
 
 	    lp_filter_size[chan] = (int) (( filter_len_bits * (float)samples_per_sec / baud) + 0.5);
 
-	    if (lp_filter_size[chan] < 10 || lp_filter_size[chan] > MAX_FILTER_SIZE) {
-	      text_color_set(DW_COLOR_ERROR);
-	      dw_printf ("gen_tone_init: INTERNAL ERROR, chan %d, lp_filter_size %d\n", chan, lp_filter_size[chan]);
-	      lp_filter_size[chan] = MAX_FILTER_SIZE / 2;
+	    if (lp_filter_size[chan] < 10) {
+	      text_color_set(DW_COLOR_DEBUG);
+	      dw_printf ("gen_tone_init: unexpected, chan %d, lp_filter_size %d < 10\n", chan, lp_filter_size[chan]);
+	      lp_filter_size[chan] = 10;
+	    }
+	    else if (lp_filter_size[chan] > MAX_FILTER_SIZE) {
+	      text_color_set(DW_COLOR_DEBUG);
+	      dw_printf ("gen_tone_init: unexpected, chan %d, lp_filter_size %d > %d\n", chan, lp_filter_size[chan], MAX_FILTER_SIZE);
+	      lp_filter_size[chan] = MAX_FILTER_SIZE;
 	    }
 
 	    fc = (float)baud * lpf_baud / (float)samples_per_sec;
@@ -358,6 +372,8 @@ void gen_tone_put_sample (int chan, int a, int sam) {
 
 	assert (save_audio_config_p->adev[a].bits_per_sample == 16);
 
+	// TODO: Should print message telling user to reduce output level.
+
 	if (sam < -32767) sam = -32767;
 	else if (sam > 32767) sam = 32767;