Setting gains

src/algorithms/signal_source/libs/rtl_tcp_dongle_info.cc

@@ -32,6 +32,7 @@
  */
 #include "rtl_tcp_dongle_info.h"
 #include <string.h>
+#include <boost/foreach.hpp>
 
 using boost::asio::ip::tcp;
 
@@ -85,6 +86,59 @@ const char *rtl_tcp_dongle_info::get_type_name () const {
     }
 }
 
+double rtl_tcp_dongle_info::clip_gain (int gain) const {
+    // the following gain values have been copied from librtlsdr
+    // all gain values are expressed in tenths of a dB
+
+    std::vector<double> gains;
+    switch (get_tuner_type()) {
+    case TUNER_E4000:
+        gains = { -10, 15, 40, 65, 90, 115, 140, 165, 190, 215,
+                  240, 290, 340, 420 };
+        break;
+    case TUNER_FC0012:
+        gains = { -99, -40, 71, 179, 192 };
+        break;
+    case TUNER_FC0013:
+        gains = { -99, -73, -65, -63, -60, -58, -54, 58, 61,
+                  63, 65, 67, 68, 70, 71, 179, 181, 182,
+                  184, 186, 188, 191, 197 };
+        break;
+    case TUNER_R820T:
+        gains = { 0, 9, 14, 27, 37, 77, 87, 125, 144, 157,
+                  166, 197, 207, 229, 254, 280, 297, 328,
+                  338, 364, 372, 386, 402, 421, 434, 439,
+                  445, 480, 496 };
+        break;
+    default:
+        // no gains
+        break;
+    }
+
+    // clip
+    if (gains.size() == 0) {
+        // no defined gains to clip to
+        return gain;
+    }
+    else {
+        double last_stop = gains.front ();
+        BOOST_FOREACH (double g, gains) {
+            g /= 10.0;
+
+            if (gain < g) {
+                if (std::abs (gain - g) < std::abs (gain - last_stop)) {
+                    return g;
+                }
+                else {
+                    return last_stop;
+                }
+            }
+            last_stop = g;
+        }
+        return last_stop;
+    }
+}
+
 bool rtl_tcp_dongle_info::is_valid () const {
     return ::memcmp (magic_, "RTL0", 4) == 0;
 }

src/algorithms/signal_source/libs/rtl_tcp_dongle_info.h

@@ -65,6 +65,8 @@ class rtl_tcp_dongle_info {
 
     const char *get_type_name () const;
 
+    double clip_gain (int gain) const;
+
     inline uint32_t get_tuner_type () const {
         return tuner_type_;
     }