Fix intermittent underruns after a restart

When using UHD without synchronous=1:
After a modulator restart, the input ZMQ buffer is nearly empty, and
the modulator actually gets blocked by the ThreadsafeQueue. This is
visible by looking at the time deltas printed in the debugging code.

This commit adds a minimal form of prebuffering (10 ETI frames) to the
ZeroMQ input, and removes the useless minimum required size for the
ThreadsafeQueue.

In synchronous=1, the issue is not visible because the TIST defines the
time to transmit, which will cause the ZMQ buffer to fill.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/Utils.h b/src/Utils.h
index 7c3129c..f023646 100644
--- a/src/Utils.h
+++ b/src/Utils.h
@@ -35,10 +35,28 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdio.h>
+#include <time.h>
 
 void printUsage(char* progName);
 
 void printVersion(void);
 
+inline long timespecdiff_us(struct timespec& oldTime, struct timespec& time)
+{
+    long tv_sec;
+    long tv_nsec;
+    if (time.tv_nsec < oldTime.tv_nsec) {
+        tv_sec = time.tv_sec - 1 - oldTime.tv_sec;
+        tv_nsec = 1000000000L + time.tv_nsec - oldTime.tv_nsec;
+    }
+    else {
+        tv_sec = time.tv_sec - oldTime.tv_sec;
+        tv_nsec = time.tv_nsec - oldTime.tv_nsec;
+    }
+
+    return tv_sec * 1000 + tv_nsec / 1000;
+}
+
+
 #endif