uhd: multi device, set timestamps without SOB on every burst in the work function

1 files changed, 23 insertions, 16 deletions

diff --git a/gr-uhd/lib/uhd_multi_usrp_sink.cc b/gr-uhd/lib/uhd_multi_usrp_sink.cc
index ee16e2928..a1d0a2584 100644
--- a/gr-uhd/lib/uhd_multi_usrp_sink.cc
+++ b/gr-uhd/lib/uhd_multi_usrp_sink.cc
@@ -56,6 +56,7 @@ public:
 
     void set_samp_rate(double rate){
         _dev->set_tx_rate(rate);
+        _sample_rate = this->get_samp_rate();
     }
 
     double get_samp_rate(void){
@@ -128,28 +129,31 @@ public:
         gr_vector_const_void_star &input_items,
         gr_vector_void_star &output_items
     ){
-        uhd::tx_metadata_t metadata;
-        metadata.start_of_burst = true;
+        //send a mid-burst packet with time spec
+        _metadata.start_of_burst = false;
+        _metadata.end_of_burst = false;
+        _metadata.has_time_spec = true;
 
-        return _dev->get_device()->send(
-            input_items, noutput_items, metadata,
+        size_t num_sent = _dev->get_device()->send(
+            input_items, noutput_items, _metadata,
             _type, uhd::device::SEND_MODE_FULL_BUFF, 1.0
         );
+
+        //increment the timespec by the number of samples sent
+        _metadata.time_spec += uhd::time_spec_t(0, num_sent, _sample_rate);
+        return num_sent;
     }
 
     //Send an empty start-of-burst packet to begin streaming.
-    //Set at a time in the near future so data will be sync'd.
+    //Set at a time in the near future to avoid late packets.
     bool start(void){
-        uhd::tx_metadata_t metadata;
-        metadata.start_of_burst = true;
-        metadata.has_time_spec = true;
-        //TODO: Time in the near future, must be less than source time in future
-        //because ethernet pause frames with throttle stream commands.
-        //It will be fixed with the invention of host-based flow control.
-        metadata.time_spec = get_time_now() + uhd::time_spec_t(0.05);
+        _metadata.start_of_burst = true;
+        _metadata.end_of_burst = false;
+        _metadata.has_time_spec = true;
+        _metadata.time_spec = get_time_now() + uhd::time_spec_t(0.01);
 
         _dev->get_device()->send(
-            gr_vector_const_void_star(_nchan), 0, metadata,
+            gr_vector_const_void_star(_nchan), 0, _metadata,
             _type, uhd::device::SEND_MODE_ONE_PACKET, 1.0
         );
         return true;
@@ -158,11 +162,12 @@ public:
     //Send an empty end-of-burst packet to end streaming.
     //Ending the burst avoids an underflow error on stop.
     bool stop(void){
-        uhd::tx_metadata_t metadata;
-        metadata.end_of_burst = true;
+        _metadata.start_of_burst = false;
+        _metadata.end_of_burst = true;
+        _metadata.has_time_spec = false;
 
         _dev->get_device()->send(
-            gr_vector_const_void_star(_nchan), 0, metadata,
+            gr_vector_const_void_star(_nchan), 0, _metadata,
             _type, uhd::device::SEND_MODE_ONE_PACKET, 1.0
         );
         return true;
@@ -172,6 +177,8 @@ protected:
     uhd::usrp::multi_usrp::sptr _dev;
     const uhd::io_type_t _type;
     size_t _nchan;
+    uhd::tx_metadata_t _metadata;
+    double _sample_rate;
 };
 
 /***********************************************************************