Added ZMQ Tx sample offset

lib/src/phy/rf/rf_zmq_imp.c

@@ -307,6 +307,9 @@ int rf_zmq_open_multi(char* args, void** h, uint32_t nof_channels)
       parse_double(args, "tx_freq", i, &tx_freq);
       tx_opts.frequency_mhz = (uint32_t)(tx_freq / 1e6);
 
+      // tx_offset
+      parse_int32(args, "tx_offset", i, &tx_opts.sample_offset);
+
       // fail_on_disconnect
       char tmp[RF_PARAM_LEN] = {};
       parse_string(args, "fail_on_disconnect", i, tmp);

lib/src/phy/rf/rf_zmq_imp_trx.h

@@ -42,6 +42,7 @@ typedef struct {
   cf_t*           zeros;
   void*           temp_buffer_convert;
   uint32_t        frequency_mhz;
+  int32_t         sample_offset;
 } rf_zmq_tx_t;
 
 typedef struct {

lib/src/phy/rf/rf_zmq_imp_tx.c

@@ -39,6 +39,7 @@ int rf_zmq_tx_open(rf_zmq_tx_t* q, rf_zmq_opts_t opts, void* zmq_ctx, char* sock
     q->socket_type   = opts.socket_type;
     q->sample_format = opts.sample_format;
     q->frequency_mhz = opts.frequency_mhz;
+    q->sample_offset = opts.sample_offset;
 
     rf_zmq_info(q->id, "Binding transmitter: %s\n", sock_args);
 
@@ -179,6 +180,19 @@ int rf_zmq_tx_baseband(rf_zmq_tx_t* q, cf_t* buffer, uint32_t nsamples)
 
   pthread_mutex_lock(&q->mutex);
 
+  if (q->sample_offset > 0) {
+    _rf_zmq_tx_baseband(q, q->zeros, (uint32_t)q->sample_offset);
+    q->sample_offset = 0;
+  } else if (q->sample_offset < 0) {
+    n = SRSLTE_MIN(-q->sample_offset, nsamples);
+    buffer += n;
+    nsamples -= n;
+    q->sample_offset += n;
+    if (nsamples == 0) {
+      return n;
+    }
+  }
+
   n = _rf_zmq_tx_baseband(q, buffer, nsamples);
 
   pthread_mutex_unlock(&q->mutex);