Shorten queue to decrease latency

src/main.c

@@ -37,7 +37,7 @@
 
 #define IQ_SAMPLES 32
 #define IQ_BLOCK_LEN (2 * IQ_SAMPLES)
-#define IQ_QUEUE_LEN 4
+#define IQ_QUEUE_LEN 2
 
 #define LO_BITS_DEPTH 15
 #define LO_WORDS (1 << (LO_BITS_DEPTH - 2))
@@ -598,6 +598,8 @@ static void do_rx()
 		if (queue_try_remove(&iq_queue, &block)) {
 			fwrite(block, IQ_BLOCK_LEN, 1, stdout);
 			fflush(stdout);
+		} else {
+			sleep_us(25);
 		}
 	}