fix: RTL-SDR bug fixes and accuracy improvements

kernel/src/Drivers/Radio/Sdr.cpp

@@ -155,7 +155,12 @@ namespace Drivers::Radio::Sdr {
         uint32_t space = RING_BYTES - r.count;
         uint32_t n = len;
         uint32_t dropped = 0;
-        if (n > space) { dropped = n - space; n = space; }
+        if (n > space) {
+            // Truncate to a whole number of I/Q byte pairs: dropping an odd
+            // count would swap I and Q for the rest of the stream.
+            n = space & ~1u;
+            dropped = len - n;
+        }
 
         uint32_t first = RING_BYTES - r.head;
         if (first > n) first = n;
@@ -241,6 +246,9 @@ namespace Drivers::Radio::Sdr {
     int Start(int handle) {
         Receiver* r = Lookup(handle, true);
         if (!r) return -1;
+        // Already streaming: a second Start must not re-arm the driver's
+        // transfer pool (it would double-queue every buffer).
+        if (r->streaming) return 0;
 
         r->lock.Acquire();
         r->head = r->count = 0;   // discard stale samples before (re)starting