diff --git a/src/streamchannel.cpp b/src/streamchannel.cpp
--- a/src/streamchannel.cpp
+++ b/src/streamchannel.cpp
@@ -20,7 +20,7 @@
 #include <limits>
 #include "streamchannel.h"
 
-StreamChannel::StreamChannel(unsigned i, const FrameBuffer* x,
+StreamChannel::StreamChannel(unsigned i, const XFrameBuffer* x,
               FrameBuffer* y, ChannelInfoModel* info)
 {
     _index = i;
@@ -38,15 +38,19 @@ unsigned StreamChannel::index() const {r
 QString StreamChannel::name() const {return _info->name(_index);};
 QColor StreamChannel::color() const {return _info->color(_index);};
 bool StreamChannel::visible() const {return _info->isVisible(_index);};
-const FrameBuffer* StreamChannel::xData() const {return _x;}
+const XFrameBuffer* StreamChannel::xData() const {return _x;}
 const FrameBuffer* StreamChannel::yData() const {return _y;}
 FrameBuffer* StreamChannel::yData() {return _y;}
 const ChannelInfoModel* StreamChannel::info() const {return _info;}
-void StreamChannel::setX(const FrameBuffer* x) {_x = x;};
+void StreamChannel::setX(const XFrameBuffer* x) {_x = x;};
+
+#include <QtDebug>
 
 double StreamChannel::findValue(double x) const
 {
-    int index = findIndex(x);
+    // int index = findIndex(x);
+    int index = _x->findIndex(x);
+    qDebug() << x << ":" << index;
     if (index >= 0)
         return _y->sample(index);
     else