diff --git a/openbr/plugins/algorithms.cpp b/openbr/plugins/algorithms.cpp
index 1d1e2fb..5526c33 100644
--- a/openbr/plugins/algorithms.cpp
+++ b/openbr/plugins/algorithms.cpp
@@ -52,7 +52,7 @@ class AlgorithmsInitializer : public Initializer
 
         Globals->abbreviations.insert("HOG", "Stream(DropFrames(5)+Cvt(Gray)+KeyPointDetector(SIFT)+ROI+Expand+Resize(32,32)+Gradient+RectRegions+Bin(0,360,8)+Hist(8)+Cat)+Contract+CatRows+KMeans(500)+Hist(500)+SVM");
         Globals->abbreviations.insert("HOF", "Stream(DropFrames(5)+KeyPointDetector(SIFT)+AggregateFrames(2)+OpticalFlow+ROI+Expand+Resize(32,32)+Gradient+RectRegions+Bin(0,360,8)+Hist(8)+Cat)+Contract+CatRows+KMeans(500)+Hist(500)");
-        Globals->abbreviations.insert("HOGHOF", "Stream(DropFrames(5)+Cvt(Gray),KeyPointDetector(SIFT)+AggregateFrames(2)+(OpticalFlow+Gradient+Bin(0,360,8)+ROI+Hist(8))/(First+Gradient+Bin(0,360,8)+ROI+Hist(8))+CatCols)+Contract+CatRows+KMeans(500)+Hist(500)");
+        Globals->abbreviations.insert("HOGHOF", "Stream(DropFrames(5)+KeyPointDetector(SIFT)+AggregateFrames(2)+(OpticalFlow++ROI+Expand+Resize(32,32)+Gradient+RectRegions+Bin(0,360,8)+Hist(8)+Cat+Contract)/(First+Cvt(Gray)+ROI+Expand+Resize(32,32)+Gradient+RectRegions+Bin(0,360,8)+Hist(8)+Cat+Contract)+CatCols)+Contract+CatRows+KMeans(500)+Hist(500)+SVM");
 
         // Generic Image Processing
         Globals->abbreviations.insert("SIFT", "Open+KeyPointDetector(SIFT)+KeyPointDescriptor(SIFT):KeyPointMatcher(BruteForce)");
diff --git a/openbr/plugins/frames.cpp b/openbr/plugins/frames.cpp
index f5f8609..fb7f507 100644
--- a/openbr/plugins/frames.cpp
+++ b/openbr/plugins/frames.cpp
@@ -27,12 +27,14 @@ private:
         (void) data;
     }
 
-    void projectUpdate(const Template &src, Template &dst)
+    void projectUpdate(const TemplateList &src, TemplateList &dst)
     {
         buffer.append(src);
         if (buffer.size() < n) return;
-        foreach (const Template &t, buffer) dst.append(t);
-        dst.file = buffer.takeFirst().file;
+        Template out;
+        foreach (const Template &t, buffer) out.append(t);
+        out.file = buffer.takeFirst().file;
+        dst.append(out);
     }
 
     void finalize(TemplateList & output)
diff --git a/openbr/plugins/meta.cpp b/openbr/plugins/meta.cpp
index 5905c31..1cfd271 100644
--- a/openbr/plugins/meta.cpp
+++ b/openbr/plugins/meta.cpp
@@ -265,6 +265,7 @@ class ContractTransform : public UntrainableMetaTransform
     virtual void project(const TemplateList &src, TemplateList &dst) const
     {
         //dst = Expanded(src);
+        if (src.empty()) return;
         Template out;
 
         foreach (const Template & t, src) {
diff --git a/openbr/plugins/opticalflow.cpp b/openbr/plugins/opticalflow.cpp
index 5246ad5..89c2044 100644
--- a/openbr/plugins/opticalflow.cpp
+++ b/openbr/plugins/opticalflow.cpp
@@ -34,7 +34,7 @@ class OpticalFlowTransform : public UntrainableMetaTransform
     void project(const Template &src, Template &dst) const
     {
         // get the two images put there by AggregateFrames
-        if (src.size() < 2) return;
+        if (src.size() != 2) qFatal("Optical Flow requires two images.");
         Mat prevImg = src[0], nextImg = src[1], flow, flowOneCh;
         if (src[0].channels() != 1) OpenCVUtils::cvtGray(src[0], prevImg);
         if (src[1].channels() != 1) OpenCVUtils::cvtGray(src[1], nextImg);
diff --git a/openbr/plugins/regions.cpp b/openbr/plugins/regions.cpp
index e6c30fa..d4363b5 100644
--- a/openbr/plugins/regions.cpp
+++ b/openbr/plugins/regions.cpp
@@ -141,7 +141,6 @@ class CatColsTransform : public UntrainableMetaTransform
 
     void project(const Template &src, Template &dst) const
     {
-        if (src.empty()) return;
         dst.file = src.file;
         Mat m = OpenCVUtils::toMatByRow(src);
         // right now this just splits src in half and joins them horizontally