USRP driver improvements.

Set bit size to be 16 for interpolators and decimators.
Match buffer size to UHD.
Don't destroy TX stream, as there appears to be a bug when recreating it.
Catch exception when checking for TX underflow.
Increase RX FIFO size, to reduce overflows at high sample rates.
Allow RX to continue streaming after receiving timeout.

plugins/samplesource/usrpinput/usrpinput.cpp

@@ -51,6 +51,7 @@ USRPInput::USRPInput(DeviceAPI *deviceAPI) :
     m_deviceAPI(deviceAPI),
     m_settings(),
     m_usrpInputThread(nullptr),
+    m_bufSamples(0),
     m_deviceDescription("USRPInput"),
     m_running(false),
     m_channelAcquired(false)
@@ -91,7 +92,9 @@ void USRPInput::destroy()
 
 bool USRPInput::openDevice()
 {
-    if (!m_sampleFifo.setSize(96000 * 4))
+    // B210 supports up to 50MSa/s, so a fairly large FIFO is probably a good idea
+    // Should it be bigger still?
+    if (!m_sampleFifo.setSize(2000000))
     {
         qCritical("USRPInput::openDevice: could not allocate SampleFifo");
         return false;
@@ -325,6 +328,9 @@ bool USRPInput::acquireChannel()
         stream_args.channels = channel_nums;
 
         m_streamId = m_deviceShared.m_deviceParams->getDevice()->get_rx_stream(stream_args);
+
+        // Match our receive buffer size to what UHD uses
+        m_bufSamples = m_streamId->get_max_num_samps();
     }
     catch (std::exception& e)
     {
@@ -375,7 +381,7 @@ bool USRPInput::start()
 
     // start / stop streaming is done in the thread.
 
-    m_usrpInputThread = new USRPInputThread(m_streamId, &m_sampleFifo);
+    m_usrpInputThread = new USRPInputThread(m_streamId, m_bufSamples, &m_sampleFifo);
     qDebug("USRPInput::start: thread created");
 
     applySettings(m_settings, true);