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, 17 insertions, 0 deletions

diff --git a/src/OutputUHD.cpp b/src/OutputUHD.cpp
index ad31be7..acc4271 100644
--- a/src/OutputUHD.cpp
+++ b/src/OutputUHD.cpp
@@ -31,6 +31,7 @@
 #include "PcDebug.h"
 #include "Log.h"
 #include "RemoteControl.h"
+#include "Utils.h"
 
 #include <boost/thread/future.hpp>
 
@@ -349,8 +350,24 @@ int OutputUHD::process(Buffer* dataIn, Buffer* dataOut)
                 " to " << dataIn->getLength();
             throw std::runtime_error("Non-constant input length!");
         }
+
+        struct timespec time_before;
+        int time_before_ret = clock_gettime(CLOCK_MONOTONIC, &time_before);
+
         mySyncBarrier.get()->wait();
 
+        struct timespec time_after;
+        int time_after_ret = clock_gettime(CLOCK_MONOTONIC, &time_after);
+
+        if (time_before_ret == 0 and time_after_ret == 0) {
+            etiLog.level(debug) << "Time delta : " <<
+                timespecdiff_us(time_before, time_after) << " us";
+        }
+        else {
+            etiLog.level(error) << "Time delta failed " <<
+                time_before_ret << " " << time_after_ret;
+        }
+
         if (!uwd.running) {
             worker.stop();
             first_run = true;