1 files changed, 14 insertions, 5 deletions
diff --git a/host/lib/include/uhdlib/transport/rx_streamer_impl.hpp b/host/lib/include/uhdlib/transport/rx_streamer_impl.hpp
index 79c196f3f..f776d9373 100644
--- a/host/lib/include/uhdlib/transport/rx_streamer_impl.hpp
+++ b/host/lib/include/uhdlib/transport/rx_streamer_impl.hpp
@@ -88,7 +88,6 @@ public:
 
         if (stream_args.args.has_key("spp")) {
             _spp = stream_args.args.cast<size_t>("spp", _spp);
-            _mtu = _spp * _convert_info.bytes_per_otw_item;
         }
     }
 
@@ -97,7 +96,8 @@ public:
     // them
     virtual void connect_channel(const size_t channel, typename transport_t::uptr xport)
     {
-        const size_t mtu = xport->get_max_payload_size();
+        const size_t mtu = xport->get_mtu();
+        _hdr_len = std::max(_hdr_len, xport->get_chdr_hdr_len());
         _zero_copy_streamer.connect_channel(channel, std::move(xport));
 
         if (mtu < _mtu) {
@@ -201,11 +201,15 @@ protected:
         return _mtu;
     }
 
-    //! Sets the MTU and calculates spp
+    //! Sets the MTU and checks spp. If spp would exceed the new MTU, it is
+    // reduced accordingly.
     void set_mtu(const size_t mtu)
     {
         _mtu = mtu;
-        _spp = _mtu / _convert_info.bytes_per_otw_item;
+        const size_t spp_from_mtu = (_mtu - _hdr_len) / _convert_info.bytes_per_otw_item;
+        if (spp_from_mtu < _spp) {
+            _spp = spp_from_mtu;
+        }
     }
 
     //! Configures sample rate for conversion of timestamp
@@ -401,7 +405,12 @@ private:
     // MTU, determined when xport is connected and modifiable by subclass
     size_t _mtu = std::numeric_limits<std::size_t>::max();
 
-    // Maximum number of samples per packet
+    // Size of CHDR header in bytes
+    size_t _hdr_len = 0;
+
+    // Maximum number of samples per packet. Note that this is not necessarily
+    // related to the MTU, it is a user-chosen value. However, it is always
+    // bounded by the MTU.
     size_t _spp = std::numeric_limits<std::size_t>::max();
 
     // Num samps remaining in buffer currently held by zero copy streamer