From 2bc59154bf1b2d47501a43cd36211c2509db2fe8 Mon Sep 17 00:00:00 2001
From: f4exb <f4exb06@gmail.com>
Date: Sun, 4 Nov 2018 18:56:57 +0100
Subject: [PATCH] SoapySDR support: output: fixed sample FIFO resizing

---
 devices/soapysdr/devicesoapysdrshared.cpp     |  4 +++
 devices/soapysdr/devicesoapysdrshared.h       |  4 +++
 .../soapysdroutput/soapysdroutput.cpp         | 32 +++++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/devices/soapysdr/devicesoapysdrshared.cpp b/devices/soapysdr/devicesoapysdrshared.cpp
index bbfabd460..e7ef10f70 100644
--- a/devices/soapysdr/devicesoapysdrshared.cpp
+++ b/devices/soapysdr/devicesoapysdrshared.cpp
@@ -18,6 +18,10 @@
 
 MESSAGE_CLASS_DEFINITION(DeviceSoapySDRShared::MsgReportBuddyChange, Message)
 
+const float  DeviceSoapySDRShared::m_sampleFifoLengthInSeconds = 0.25;
+const int    DeviceSoapySDRShared::m_sampleFifoMinSize = 75000; // 300 kS/s knee
+const int    DeviceSoapySDRShared::m_sampleFifoMinSize32 = 150000; // Fixed for interpolation by 32
+
 DeviceSoapySDRShared::DeviceSoapySDRShared() :
     m_device(0),
     m_channel(-1),
diff --git a/devices/soapysdr/devicesoapysdrshared.h b/devices/soapysdr/devicesoapysdrshared.h
index 36d54c2bc..85adc878a 100644
--- a/devices/soapysdr/devicesoapysdrshared.h
+++ b/devices/soapysdr/devicesoapysdrshared.h
@@ -87,6 +87,10 @@ public:
     int m_channel; //!< allocated channel (-1 if none)
     SoapySDRInput *m_source;
     SoapySDROutput *m_sink;
+
+    static const float m_sampleFifoLengthInSeconds;
+    static const int   m_sampleFifoMinSize;
+    static const int   m_sampleFifoMinSize32;
 };
 
 
diff --git a/plugins/samplesink/soapysdroutput/soapysdroutput.cpp b/plugins/samplesink/soapysdroutput/soapysdroutput.cpp
index 325cd09a3..447bb3c58 100644
--- a/plugins/samplesink/soapysdroutput/soapysdroutput.cpp
+++ b/plugins/samplesink/soapysdroutput/soapysdroutput.cpp
@@ -621,6 +621,38 @@ bool SoapySDROutput::applySettings(const SoapySDROutputSettings& settings, bool
     xlatedDeviceCenterFrequency -= settings.m_transverterMode ? settings.m_transverterDeltaFrequency : 0;
     xlatedDeviceCenterFrequency = xlatedDeviceCenterFrequency < 0 ? 0 : xlatedDeviceCenterFrequency;
 
+    // resize FIFO
+    if ((m_settings.m_devSampleRate != settings.m_devSampleRate) || (m_settings.m_log2Interp != settings.m_log2Interp) || force)
+    {
+        SoapySDROutputThread *soapySDROutputThread = findThread();
+        SampleSourceFifo *fifo = 0;
+
+        if (soapySDROutputThread)
+        {
+            fifo = soapySDROutputThread->getFifo(requestedChannel);
+            soapySDROutputThread->setFifo(requestedChannel, 0);
+        }
+
+        int fifoSize;
+
+        if (settings.m_log2Interp >= 5)
+        {
+            fifoSize = DeviceSoapySDRShared::m_sampleFifoMinSize32;
+        }
+        else
+        {
+            fifoSize = std::max(
+                (int) ((settings.m_devSampleRate/(1<<settings.m_log2Interp)) * DeviceSoapySDRShared::m_sampleFifoLengthInSeconds),
+                DeviceSoapySDRShared::m_sampleFifoMinSize);
+        }
+
+        m_sampleSourceFifo.resize(fifoSize);
+
+        if (fifo) {
+            soapySDROutputThread->setFifo(requestedChannel, &m_sampleSourceFifo);
+        }
+    }
+
     if ((m_settings.m_devSampleRate != settings.m_devSampleRate) || force)
     {
         forwardChangeOwnDSP = true;