Documents improvements

include/nrsc5.h

@@ -44,6 +44,10 @@
 #define NRSC5_MIME_TTN_STM_TRAFFIC  0xFF8422D7
 #define NRSC5_MIME_TTN_STM_WEATHER  0xEF042E96
 
+#define NRSC5_SAMPLE_RATE_CU8   1488375
+#define NRSC5_SAMPLE_RATE_CS16  744187.5
+#define NRSC5_SAMPLE_RATE_AUDIO 44100
+
 enum
 {
     NRSC5_MODE_FM,
@@ -593,6 +597,7 @@ void nrsc5_set_callback(nrsc5_t *st, nrsc5_callback_t callback, void *opaque);
  * @param[in] st  pointer to an `nrsc5_t` session object
  * @param[in] samples  pointer to an array 8-bit unsigned samples
  * @param[in] length   the number of samples in the array
+ * @see NRSC5_SAMPLE_RATE_CU8 for required sample rate
  * @return 0 on success, nonzero on error
  *
  */
@@ -605,6 +610,7 @@ int nrsc5_pipe_samples_cu8(nrsc5_t *st, const uint8_t *samples, unsigned int len
  * @param[in] st  pointer to an `nrsc5_t` session object
  * @param[in] samples  pointer to an array 16-bit signed samples
  * @param[in] length   the number of samples in the array
+ * @see NRSC5_SAMPLE_RATE_CS16 for required sample rate
  * @return 0 on success, nonzero on error
  *
  */

src/acquire.c

@@ -266,7 +266,7 @@ void acquire_cfo_adjust(acquire_t *st, int cfo)
         return;
 
     st->cfo += cfo;
-    hz = (float) st->cfo * SAMPLE_RATE / st->fft;
+    hz = (float) st->cfo * NRSC5_SAMPLE_RATE_CU8 / st->fft;
     hz /= (st->mode == NRSC5_MODE_FM ? DECIMATION_FACTOR_FM : DECIMATION_FACTOR_AM);
 
     log_info("CFO: %f Hz", hz);

src/defines.h

@@ -8,8 +8,6 @@
 #include <complex.h>
 #include <math.h>
 
-// Sample rate before decimation
-#define SAMPLE_RATE 1488375
 // FFT length in samples
 #define FFT_FM 2048
 #define FFT_AM 256

src/main.c

@@ -78,7 +78,7 @@ typedef struct {
 
 static ao_sample_format sample_format = {
     16,
-    44100,
+    NRSC5_SAMPLE_RATE_AUDIO,
     2,
     AO_FMT_NATIVE,
     "L,R"
@@ -308,7 +308,7 @@ static void callback(const nrsc5_event_t *evt, void *opaque)
             st->audio_packets++;
             st->audio_bytes += evt->hdc.count * sizeof(evt->hdc.data[0]);
             if (st->audio_packets >= 32) {
-                log_info("Audio bit rate: %.1f kbps", (float)st->audio_bytes * 8 * 44100 / 2048 / st->audio_packets / 1000);
+                log_info("Audio bit rate: %.1f kbps", (float)st->audio_bytes * 8 * NRSC5_SAMPLE_RATE_AUDIO / 2048 / st->audio_packets / 1000);
                 st->audio_packets = 0;
                 st->audio_bytes = 0;
             }

src/nrsc5.c

@@ -64,7 +64,7 @@ static int do_auto_gain(nrsc5_t *st)
         {
             // there is no good way to wait for samples after the new gain was applied
             // dump 250ms of samples and hope for the best
-            rtltcp_reset_buffer(st->rtltcp, (SAMPLE_RATE / 4) * 2);
+            rtltcp_reset_buffer(st->rtltcp, (NRSC5_SAMPLE_RATE_CU8 / 4) * 2);
         }
 
         st->auto_gain_snr_ready = 0;
@@ -309,7 +309,7 @@ NRSC5_API int nrsc5_open(nrsc5_t **result, int device_index)
     if (rtlsdr_open(&st->dev, device_index) != 0)
         goto error_init;
 
-    err = rtlsdr_set_sample_rate(st->dev, SAMPLE_RATE);
+    err = rtlsdr_set_sample_rate(st->dev, NRSC5_SAMPLE_RATE_CU8);
     if (err) goto error;
     err = rtlsdr_set_tuner_gain_mode(st->dev, 1);
     if (err) goto error;
@@ -358,7 +358,7 @@ NRSC5_API int nrsc5_open_rtltcp(nrsc5_t **result, int socket)
     if (st->rtltcp == NULL)
         goto error;
 
-    err = rtltcp_set_sample_rate(st->rtltcp, SAMPLE_RATE);
+    err = rtltcp_set_sample_rate(st->rtltcp, NRSC5_SAMPLE_RATE_CU8);
     if (err) goto error;
     err = rtltcp_set_tuner_gain_mode(st->rtltcp, 1);
     if (err) goto error;

support/cli.py

@@ -92,7 +92,7 @@ def run(self):
             self.wav_output = wave.open(self.args.o, "wb")
             self.wav_output.setnchannels(2)
             self.wav_output.setsampwidth(2)
-            self.wav_output.setframerate(44100)
+            self.wav_output.setframerate(nrsc5.SAMPLE_RATE_AUDIO)
         else:
             audio_thread = threading.Thread(target=self.audio_worker)
             audio_thread.start()
@@ -145,7 +145,7 @@ def audio_worker(self):
             index = audio.get_default_output_device_info()["index"]
             stream = audio.open(format=pyaudio.paInt16,
                                 channels=2,
-                                rate=44100,
+                                rate=nrsc5.SAMPLE_RATE_AUDIO,
                                 output_device_index=index,
                                 output=True)
         except OSError:

support/nrsc5.py

@@ -29,6 +29,11 @@ class EventType(enum.Enum):
     PACKET = 13
 
 
+SAMPLE_RATE_CU8 = 1488375
+SAMPLE_RATE_CS16 = 744187.5
+SAMPLE_RATE_AUDIO = 44100
+
+
 class ServiceType(enum.Enum):
     AUDIO = 0
     DATA = 1