rtl_test: add ppm measurement

Use with caution, the result highly depends on the
accuracy of the clocksource your machine uses.
On some machines it may be quite accurate, on
others completely off.

Signed-off-by: Steve Markgraf <steve@steve-m.de>

configure.ac

@@ -39,6 +39,9 @@ AC_CHECK_LIB(pthread, pthread_create, [LIBS="$LIBS -lpthread"])
 dnl libmath (for rtl_fm)
 AC_CHECK_LIB(m, atan2, [LIBS="$LIBS -lm"])
 
+dnl librealtime (for rtl_test)
+AC_CHECK_LIB(rt, clock_gettime, [LIBS="$LIBS"])
+
 # The following test is taken from WebKit's webkit.m4
 saved_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -fvisibility=hidden "

src/CMakeLists.txt

@@ -94,6 +94,11 @@ target_link_libraries(rtl_fm rtlsdr_shared
     ${CMAKE_THREAD_LIBS_INIT}
     m
 )
+if(APPLE)
+    target_link_libraries(rtl_test m)
+else()
+    target_link_libraries(rtl_test m rt)
+endif()
 endif()
 
 if(WIN32)

src/Makefile.am

@@ -19,7 +19,7 @@ rtl_tcp_SOURCES      = rtl_tcp.c
 rtl_tcp_LDADD        = librtlsdr.la
 
 rtl_test_SOURCES      = rtl_test.c
-rtl_test_LDADD        = librtlsdr.la
+rtl_test_LDADD        = librtlsdr.la $(LIBM)
 
 rtl_fm_SOURCES      = rtl_fm.c
 rtl_fm_LDADD        = librtlsdr.la $(LIBM)

src/rtl_test.c

@@ -21,6 +21,13 @@
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <math.h>
+
+#ifdef __APPLE__
+#include <sys/time.h>
+#else
+#include <time.h>
+#endif
 
 #ifndef _WIN32
 #include <unistd.h>
@@ -39,9 +46,25 @@
 
 #define MHZ(x)	((x)*1000*1000)
 
+#define PPM_DURATION			10
+
 static int do_exit = 0;
 static rtlsdr_dev_t *dev = NULL;
 
+static int ppm_benchmark = 0;
+static int64_t ppm_count = 0L;
+static int64_t ppm_total = 0L;
+
+#ifndef _WIN32
+static struct timespec ppm_start;
+static struct timespec ppm_recent;
+static struct timespec ppm_now;
+#endif
+
+#ifdef __APPLE__
+static struct timeval tv;
+#endif
+
 void usage(void)
 {
 	fprintf(stderr,
@@ -50,6 +73,9 @@ void usage(void)
 		"\t[-s samplerate (default: 2048000 Hz)]\n"
 		"\t[-d device_index (default: 0)]\n"
 		"\t[-t enable Elonics E4000 tuner benchmark]\n"
+		#ifndef _WIN32
+		"\t[-p enable PPM error measurement]\n"
+		#endif
 		"\t[-b output_block_size (default: 16 * 16384)]\n"
 		"\t[-S force sync output (default: async)]\n");
 	exit(1);
@@ -81,6 +107,8 @@ uint8_t bcnt, uninit = 1;
 static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
 {
 	uint32_t i, lost = 0;
+	int64_t ns;
+	double perf_sec;
 
 	if (uninit) {
 		bcnt = buf[0];
@@ -98,6 +126,35 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
 
 	if (lost)
 		printf("lost at least %d bytes\n", lost);
+
+	if (!ppm_benchmark) {
+		return;
+	}
+	ppm_count += (int64_t)len;
+#ifndef _WIN32
+	#ifndef __APPLE__
+	clock_gettime(CLOCK_REALTIME, &ppm_now);
+	#else
+	gettimeofday(&tv, NULL);
+	ppm_now.tv_sec = tv.tv_sec;
+	ppm_now.tv_nsec = tv.tv_usec*1000;
+	#endif
+	if (ppm_now.tv_sec - ppm_recent.tv_sec > PPM_DURATION) {
+		ns = 1000000000L * (int64_t)(ppm_now.tv_sec - ppm_recent.tv_sec);
+		ns += (int64_t)(ppm_now.tv_nsec - ppm_recent.tv_nsec);
+		printf("real sample rate: %i\n",
+		(int)((1000000000L * ppm_count / 2L) / ns));
+		#ifndef __APPLE__
+		clock_gettime(CLOCK_REALTIME, &ppm_recent);
+		#else
+		gettimeofday(&tv, NULL);
+		ppm_recent.tv_sec = tv.tv_sec;
+		ppm_recent.tv_nsec = tv.tv_usec*1000;
+		#endif
+		ppm_total += ppm_count / 2L;
+		ppm_count = 0L;
+	}
+#endif
 }
 
 void e4k_benchmark(void)
@@ -162,8 +219,11 @@ int main(int argc, char **argv)
 	int device_count;
 	int count;
 	int gains[100];
+	int real_rate;
+	int64_t ns;
+	double perf_sec;
 
-	while ((opt = getopt(argc, argv, "d:s:b:tS::")) != -1) {
+	while ((opt = getopt(argc, argv, "d:s:b:tpS::")) != -1) {
 		switch (opt) {
 		case 'd':
 			dev_index = atoi(optarg);
@@ -177,6 +237,9 @@ int main(int argc, char **argv)
 		case 't':
 			tuner_benchmark = 1;
 			break;
+		case 'p':
+			ppm_benchmark = PPM_DURATION;
+			break;
 		case 'S':
 			sync_mode = 1;
 			break;
@@ -260,6 +323,21 @@ int main(int argc, char **argv)
 	if (r < 0)
 		fprintf(stderr, "WARNING: Failed to reset buffers.\n");
 
+	if (ppm_benchmark && !sync_mode) {
+		fprintf(stderr, "Reporting PPM error measurement every %i seconds...\n", ppm_benchmark);
+		fprintf(stderr, "Press ^C after a few minutes.\n");
+#ifdef __APPLE__
+		gettimeofday(&tv, NULL);
+		ppm_recent.tv_sec = tv.tv_sec;
+		ppm_recent.tv_nsec = tv.tv_usec*1000;
+		ppm_start.tv_sec = tv.tv_sec;
+		ppm_start.tv_nsec = tv.tv_usec*1000;
+#elif __unix__
+		clock_gettime(CLOCK_REALTIME, &ppm_recent);
+		clock_gettime(CLOCK_REALTIME, &ppm_start);
+#endif
+	}
+
 	if (sync_mode) {
 		fprintf(stderr, "Reading samples in sync mode...\n");
 		while (!do_exit) {
@@ -280,8 +358,18 @@ int main(int argc, char **argv)
 				      DEFAULT_ASYNC_BUF_NUMBER, out_block_size);
 	}
 
-	if (do_exit)
+	if (do_exit) {
 		fprintf(stderr, "\nUser cancel, exiting...\n");
+		if (ppm_benchmark) {
+#ifndef _WIN32
+			ns = 1000000000L * (int64_t)(ppm_recent.tv_sec - ppm_start.tv_sec);
+			ns += (int64_t)(ppm_recent.tv_nsec - ppm_start.tv_nsec);
+			real_rate = (int)(ppm_total * 1000000000L / ns);
+			printf("Cumulative PPM error: %i\n",
+			(int)round((double)(1000000 * (real_rate - (int)samp_rate)) / (double)samp_rate));
+#endif
+		}
+	}
 	else
 		fprintf(stderr, "\nLibrary error %d, exiting...\n", r);