diff --git a/modules/AbsoluteFrameDifference.cpp b/modules/AbsoluteFrameDifference.cpp
index 46130b0..5dac1ac 100644
--- a/modules/AbsoluteFrameDifference.cpp
+++ b/modules/AbsoluteFrameDifference.cpp
@@ -43,6 +43,7 @@ AbsoluteFrameDifference::AbsoluteFrameDifference()
 
 Bool AbsoluteFrameDifference::create( std::vector<PlaYUVerFrame*> apcFrameList )
 {
+  _BASIC_MODULE_API_2_CHECK_
   m_pcFrameDifference = new PlaYUVerFrame( apcFrameList[0]->getWidth(), apcFrameList[0]->getHeight(), PlaYUVerFrame::GRAY );
   return true;
 }
diff --git a/modules/DisparityStereoVar.cpp b/modules/DisparityStereoVar.cpp
index 424cdf9..907787e 100644
--- a/modules/DisparityStereoVar.cpp
+++ b/modules/DisparityStereoVar.cpp
@@ -57,6 +57,7 @@ DisparityStereoVar::DisparityStereoVar()
 
 Bool DisparityStereoVar::create( std::vector<PlaYUVerFrame*> apcFrameList )
 {
+  _BASIC_MODULE_API_2_CHECK_
   m_pcDisparityFrame = new PlaYUVerFrame( apcFrameList[0]->getWidth(), apcFrameList[0]->getHeight(), PlaYUVerFrame::GRAY );
   m_cStereoVar.minDisp = -( ( ( apcFrameList[0]->getWidth() / 8 ) + 15 ) & -16 );
   return true;
diff --git a/modules/FrameDifference.cpp b/modules/FrameDifference.cpp
index f11ebe3..b524811 100644
--- a/modules/FrameDifference.cpp
+++ b/modules/FrameDifference.cpp
@@ -44,6 +44,7 @@ FrameDifference::FrameDifference()
 
 Bool FrameDifference::create( std::vector<PlaYUVerFrame*> apcFrameList )
 {
+  _BASIC_MODULE_API_2_CHECK_
   UInt bitsPixel = ( apcFrameList[0]->getBitsPel() + 1 ) & 0x0F;
   m_iMaxDiffValue = ( 1 << ( bitsPixel - 1 ) );
   m_pcFrameDifference = new PlaYUVerFrame( apcFrameList[0]->getWidth(), apcFrameList[0]->getHeight(), PlaYUVerFrame::GRAY, bitsPixel );
diff --git a/modules/PlaYUVerModuleIf.h b/modules/PlaYUVerModuleIf.h
index 81b4dcd..f6e85a6 100644
--- a/modules/PlaYUVerModuleIf.h
+++ b/modules/PlaYUVerModuleIf.h
@@ -39,6 +39,13 @@ public: \
   static PlaYUVerModuleIf* Create() { return new X(); } \
   void Delete() { delete this; }
 
+#define _BASIC_MODULE_API_2_CHECK_ \
+if( apcFrameList.size() != m_uiNumberOfFrames ) \
+  return false; \
+for( UInt i = 0; i < apcFrameList.size(); i++ ) \
+  if( !apcFrameList[i] ) \
+  return false;
+
 enum  // Module API
 {
   MODULE_API_1,
@@ -57,8 +64,11 @@ enum  // Module type
 enum Module_NumberOfFrames
 {
   MODULE_REQUIRES_ONE_FRAME = 1,
-  MODULE_REQUIRES_TWO_FRAMES = 2,
-  MODULE_REQUIRES_THREE_FRAMES = 3,
+  MODULE_REQUIRES_TWO_FRAMES,
+  MODULE_REQUIRES_THREE_FRAMES,
+  MODULE_REQUIRES_FOUR_FRAMES,
+  MODULE_REQUIRES_FIVE_FRAMES,
+  MODULE_REQUIRES_SIX_FRAMES,
 };
 
 enum Module_Requirements
@@ -86,6 +96,7 @@ public:
   PlaYUVerModuleIf()
   {
     m_iModuleAPI = MODULE_API_1;
+    m_uiModuleRequirements = MODULE_REQUIRES_NOTHING;
   }
   virtual ~PlaYUVerModuleIf()
   {