Fix filtering

src/generate_waveforms.py

@@ -37,7 +37,7 @@ def generate_bit_in_context(pattern, name):
     
     shapedSamples = rds.unmodulated_signal(pattern, sample_rate)
 
-    out = shapedSamples[offset:offset+l*count]
+    out = shapedSamples #[offset:offset+l*count]
 
     iout = (out * 20000./max(abs(out)) ).astype(numpy.dtype('>i2'))
     wavfile.write(u"waveform_{}.wav".format(name), sample_rate, iout)
@@ -46,11 +46,11 @@ def generate_bit_in_context(pattern, name):
         name = name,
         values = u", ".join(map(format_number, out))))
     
-    outh.write(u"extern float waveform_{name}[];\n".format(name=name))
+    outh.write(u"extern float waveform_{name}[{size}];\n".format(name=name, size=len(out)))
 
 
-generate_bit_in_context([0, 0, 0], "identical")
-generate_bit_in_context([0, 1, 0], "different")
+generate_bit_in_context([1], "biphase")
+#generate_bit_in_context([0, 1, 0], "different")
 
 outc.close()
 outh.close()

src/rds.c

@@ -41,6 +41,7 @@ struct {
 
 #define BITS_PER_GROUP (GROUP_LENGTH * (BLOCK_SIZE+POLY_DEG))
 #define SAMPLES_PER_BIT 192
+#define FILTER_SIZE (sizeof(waveform_biphase)/sizeof(float))
 
 
 uint16_t offset_words[] = {0x0FC, 0x198, 0x168, 0x1B4};
@@ -117,17 +118,20 @@ void get_rds_group(int *buffer) {
 void get_rds_samples(float *buffer, int count) {
     static int bit_buffer[BITS_PER_GROUP];
     static int bit_pos = BITS_PER_GROUP;
+    static float sample_buffer[2*FILTER_SIZE] = {0};
     
     static int prev_output = 0;
     static int cur_output = 0;
     static int cur_bit = 0;
-    static int sample_pos = SAMPLES_PER_BIT;
-    static float *current_waveform = NULL;
+    static int sample_count = SAMPLES_PER_BIT;
     static int inverting = 0;
     static int phase = 0;
-    
+
+    static int in_sample_index = 0;
+    static int out_sample_index = FILTER_SIZE;
+        
     for(int i=0; i<count; i++) {
-        if(sample_pos >= SAMPLES_PER_BIT) {
+        if(sample_count >= SAMPLES_PER_BIT) {
             if(bit_pos >= BITS_PER_GROUP) {
                 get_rds_group(bit_buffer);
                 bit_pos = 0;
@@ -138,18 +142,29 @@ void get_rds_samples(float *buffer, int count) {
             prev_output = cur_output;
             cur_output = prev_output ^ cur_bit;
             
-            // select appropriate waveform
-            current_waveform = (prev_output == cur_output) ? 
-                                            waveform_identical : waveform_different;
-    
-            inverting = (prev_output == 0) ? 1 : -1;
+            inverting = (cur_output == 1) ? 1 : -1;
+            
+            float *src = waveform_biphase;
+            int idx = in_sample_index;
+            for(int j=0; j<FILTER_SIZE; j++) {
+                //printf("%d ", j); fflush(stdout);
+                if(j<FILTER_SIZE-SAMPLES_PER_BIT) {
+                    sample_buffer[idx++] += (*src++) * inverting;
+                } else {
+                    sample_buffer[idx++] = (*src++) * inverting;
+                }
+                if(idx >= 2*FILTER_SIZE) idx = 0;
+            }
+            in_sample_index += SAMPLES_PER_BIT;
+            if(in_sample_index >= 2*FILTER_SIZE) in_sample_index -= 2*FILTER_SIZE;
             
             bit_pos++;
-            sample_pos = 0;
+            sample_count = 0;
             //printf("%d", cur_bit); fflush(stdout);
         }
         
-        float sample = current_waveform[sample_pos] * inverting;
+        float sample = sample_buffer[out_sample_index++];
+        if(out_sample_index >= 2*FILTER_SIZE) out_sample_index = 0;
         
         // modulate at 57 kHz
         // use phase for this
@@ -163,7 +178,7 @@ void get_rds_samples(float *buffer, int count) {
         if(phase >= 4) phase = 0;
         
         *buffer++ = sample;
-        sample_pos++;
+        sample_count++;
     }
 }
 

src/rds_wav.c

@@ -2,19 +2,23 @@
 
 #include "rds.h"
 
-#define LENGTH 99840
+#define LENGTH 100000
 
 /* Simple test program */
 int main(int argc, char **argv) {
-    set_rds_params(0x1234, "Hello");
+    set_rds_params(0x1234, "Hello!  World of the RaspberryPi!");
     
     float buffer[LENGTH];
+    int count = 0;
     
-    get_rds_samples(buffer, LENGTH);
-    
-    for(int j=0; j<50; j++) {
+    for(int j=0; j<20; j++) {
+        get_rds_samples(buffer, LENGTH);
+
+        fprintf(stderr, "Iteration %d count=%d\n", j, count);
+
         for(int i=0; i<LENGTH; i++) {
-            printf("%c", (((int)(buffer[i]*70))));
+            printf("%c", (((int)(buffer[i]*50))));
+            count++;
         }
     }
 }

src/waveforms.h

@@ -4,5 +4,4 @@
    Released under the GNU GPL v3 license.
 */
 
-extern float waveform_identical[];
-extern float waveform_different[];
+extern float waveform_biphase[575];