diff --git a/Core/src/ThreadGroup.cpp b/Core/src/ThreadGroup.cpp
index 12a2aec..83c4bd1 100644
--- a/Core/src/ThreadGroup.cpp
+++ b/Core/src/ThreadGroup.cpp
@@ -1,4 +1,5 @@
 #include "ThreadGroup.h"
+#include "BC7Compressor.h"
 
 #include <stdlib.h>
 #include <stdio.h>
@@ -22,18 +23,35 @@ void CmpThread::operator()() {
   }
 
   m_Barrier->wait();
+
+  (*m_CmpFunc)(m_InBuf, m_OutBuf, m_Width, m_Height);
 }
 
 
-ThreadGroup::ThreadGroup( int numThreads, const ImageFile &, CompressionFunc func, unsigned char *outBuf )
+ThreadGroup::ThreadGroup( int numThreads, const ImageFile &image, CompressionFunc func, unsigned char *outBuf )
   : m_Barrier(new boost::barrier(numThreads))
   , m_NumThreads(numThreads)
   , m_ActiveThreads(0)
-{ }
+  , m_Func(func)
+  , m_Image(image)
+  , m_OutBuf(outBuf)
+{ 
+  for(int i = 0; i < kMaxNumThreads; i++)
+    m_Threads[i].m_Barrier = m_Barrier;
+}
 
 ThreadGroup::~ThreadGroup() {
   delete m_Barrier;
 }
+unsigned int ThreadGroup::GetCompressedBlockSize() {
+  if(m_Func == BC7C::CompressImageBC7) return 16;
+  if(m_Func == BC7C::CompressImageBC7SIMD) return 16;
+}
+
+unsigned int ThreadGroup::GetUncompressedBlockSize() {
+  if(m_Func == BC7C::CompressImageBC7) return 64;
+  if(m_Func == BC7C::CompressImageBC7SIMD) return 64;
+}
 
 void ThreadGroup::Start() {
 
@@ -42,12 +60,36 @@ void ThreadGroup::Start() {
     return;
   }
 
+  // Make sure that the image dimensions are multiples of 4
+  assert((m_Image.GetWidth() & 3) == 0);
+  assert((m_Image.GetHeight() & 3) == 0);
+
+  // We can assume that the image data is in block stream order
+  // so, the size of the data given to each thread will be (nb*4)x4
+  int numBlocks = (m_Image.GetWidth() * m_Image.GetHeight()) / 16;
+
+  int blocksProcessed = 0;
+  int blocksPerThread = (numBlocks/m_NumThreads) + ((numBlocks % m_NumThreads)? 1 : 0);
+
   for(int i = 0; i < m_NumThreads; i++) {
 
     if(m_ActiveThreads >= kMaxNumThreads)
       break;
 
+    int numBlocksThisThread = blocksPerThread;
+    if(blocksProcessed + numBlocksThisThread > numBlocks) {
+      numBlocksThisThread = numBlocks - blocksProcessed;
+    }
+
     CmpThread &t = m_Threads[m_ActiveThreads];
+    t.m_Height = 4;
+    t.m_Width = numBlocksThisThread * 4;
+    t.m_CmpFunc = m_Func;
+    t.m_OutBuf = m_OutBuf + (blocksProcessed * GetCompressedBlockSize());
+    t.m_InBuf = m_Image.GetPixels() + (blocksProcessed * GetUncompressedBlockSize());
+
+    blocksProcessed += numBlocksThisThread;
+    
     m_ThreadHandles[m_ActiveThreads] = new boost::thread(t);
 
     m_ActiveThreads++;
diff --git a/Core/src/ThreadGroup.h b/Core/src/ThreadGroup.h
index a0605bc..bb2a5ce 100644
--- a/Core/src/ThreadGroup.h
+++ b/Core/src/ThreadGroup.h
@@ -42,7 +42,7 @@ class ThreadGroup {
   const StopWatch &GetStopWatch() const { return m_StopWatch; }
 
  private:
-  boost::barrier *m_Barrier;
+  boost::barrier *const m_Barrier;
 
   static const int kMaxNumThreads = 256;
   const int m_NumThreads;
@@ -52,6 +52,14 @@ class ThreadGroup {
   CmpThread m_Threads[kMaxNumThreads];
   boost::thread *m_ThreadHandles[kMaxNumThreads];
 
+  // State variables.
+  const ImageFile &m_Image;
+  const CompressionFunc m_Func;
+  unsigned char *m_OutBuf;
+
+  unsigned int GetCompressedBlockSize();
+  unsigned int GetUncompressedBlockSize();
+
   StopWatch m_StopWatch;
 };