server: comments + measure spectrum in dB

server/bits.c

@@ -8,17 +8,20 @@
 
 #if OUR_ENDIAN != TARGET_ENDIAN
 
+// Convert 4 bytes to target endian
 void LE32(void *x) {
   uint32_t i;
   memcpy(&i, x, sizeof(i));
-  i = htobe32(i);
+  i = htole32(i);
   memcpy(x, &i, sizeof(i));
 }
 
+// Convert 2 bytes to target endian
+// ofc a more efficient implementation can be imagined
 void LE16(void *x) {
   uint16_t i;
   memcpy(&i, x, sizeof(i));
-  i = htobe16(i);
+  i = htole16(i);
   memcpy(x, &i, sizeof(i));
 }
 

server/client_parser.c

@@ -32,6 +32,9 @@ extern char* recpath;
 
 extern FILE * sdr_cmd;
 
+/* Send RUNNING_XLATER to the originating client (respecting remoteID) and then
+ *  to all other clients (with ID -1)
+ */
 void msg_running_xlater(tcp_cli_t * me, worker * w) {
 
   C2s__SRVRUNNINGXLATER s = C2S__SRV__RUNNING__XLATER__INIT;
@@ -76,6 +79,7 @@ void msg_running_xlater(tcp_cli_t * me, worker * w) {
   free(buf);
 }
 
+/* Send SRV_INFO to client *me */
 void msg_server_info(tcp_cli_t * me, bool toall) {
   C2s__SRVINFO s = C2S__SRV__INFO__INIT;
 
@@ -120,6 +124,7 @@ void msg_server_info(tcp_cli_t * me, bool toall) {
   free(buf);
 }
 
+/* Send DESTROYED_XLATER to all clients */
 void msg_destroyed_xlater(int32_t xid) {
   C2s__SRVDESTROYEDXLATER s = C2S__SRV__DESTROYED__XLATER__INIT;
 
@@ -146,9 +151,15 @@ void msg_destroyed_xlater(int32_t xid) {
   free(buf);
 }
 
+/* Main loop parsing messages from clients
+ * *me - originating client
+ * *buf2 - the message (incl. type header, but excl. length)
+ * len - length of the message
+ */
 int parse_client_req(tcp_cli_t * me, const uint8_t * buf2, int32_t len) {
   int type = ((int*)buf2)[0]; LE32(&type);
 
+  // make protobufs happy with unsigned
   const uint8_t * buf = buf2 + sizeof(int32_t);
   len -= sizeof(int32_t); // strip message type
 

server/init.sh

-#!/bin/bash -e
+#!/bin/bash
 
 if [ $# -ne 3 ]; then
   echo "Usage: $0 device rate ppm"
@@ -22,5 +22,4 @@ echo "Server PID $spid, use 'gdb ./server $spid -ex c' to debug"
 trap "kill $spid" SIGINT SIGTERM
 
 ./osmosdr-input.py -d "$1" -r "$2" -i "$tune" -o "$sdr" -f "$freq" -g "$gain" -p "$ppm"
-
 kill $spid

server/metadata.c

@@ -19,6 +19,7 @@ float* fftw_avg;
 fftwf_complex *fftw_in, *fftw_out;
 fftwf_plan p;
 
+/* Return i-th coefficient of Hamming window of a given length */
 float hamming(int i, int length) {
   double a, b, w, N1;
   a = 25.0/46.0;
@@ -28,6 +29,7 @@ float hamming(int i, int length) {
   return w;
 }
 
+/* allocate FFTW buffers and window and init plan */
 void fftw_init(int N) {
 
   if(fftw_in != NULL) {
@@ -51,6 +53,11 @@ void fftw_init(int N) {
   fftsize = N;
 }
 
+/* Calculate spectrum of packet *pkt and write it to pkt->spectrum
+ * spp - how many waterfall lines to compute
+ * fftskip - distance between beginning of transforms (we don't usually compute
+ *  side-by-side or even overlapping FFT, but rather sample the signal once a while)
+ */
 void calc_spectrum(sdr_packet * pkt, int spp, int fftskip) {
   if(fftw_window == NULL) {
     err(EXIT_FAILURE, "Internal consistency, calling calc_spectrum before fftw_init");
@@ -100,7 +107,8 @@ void calc_spectrum(sdr_packet * pkt, int spp, int fftskip) {
         } else {
           fftw_avg[k] *= hypotf(v1, v2);
         }*/
-        fftw_avg[k] += logf(hypotf(v1, v2) * dftscale);
+        fftw_avg[k] += log10f((v1*v1 + v2*v2)/fftsize);
+        //fftw_avg[k] += logf(hypotf(v1, v2) * dftscale);
 
       }
 
@@ -109,7 +117,7 @@ void calc_spectrum(sdr_packet * pkt, int spp, int fftskip) {
     }
 
     for(int k = 0; k<fftsize; k++) {
-      fftw_avg[k] = fftw_avg[k] / iters;
+      fftw_avg[k] = fftw_avg[k] / (iters/10);
     }
 
     /* Per FFTW documentation:
@@ -123,6 +131,10 @@ void calc_spectrum(sdr_packet * pkt, int spp, int fftskip) {
 
 }
 
+/* Calculate histogram of first npoints samples
+ * write it to pkt->histo
+ * npoints <= UINT16_MAX as histo is currently array of 16-bits
+ */
 void calc_histogram(sdr_packet * pkt, int npoints) {
   memset(pkt->histo, 0, HISTOGRAM_RES * sizeof(uint16_t));
   for(int i = 0; i<npoints; i++) {

server/xlate_worker.c

@@ -31,6 +31,7 @@ extern SLIST_HEAD(worker_head_t, worker) worker_head;
 
 int widx;
 
+/* Calculate the maximum amplitude a filter can produce. */
 float calc_max_amplitude(float * taps, int tapslen) {
 
   float acc = 0;
@@ -42,6 +43,7 @@ float calc_max_amplitude(float * taps, int tapslen) {
 
 }
 
+/* Rotate the low-pass filter, so it becomes band-pass. */
 float * get_complex_taps(float * taps, int tapslen, float rotate) {
   size_t align = volk_get_alignment();
   float * ctaps = volk_safe_malloc(tapslen * COMPLEX * sizeof(float), align);