From 88fae6224b54ecf92ac6e3ae5083c3f352adc798 Mon Sep 17 00:00:00 2001

From: Anuradha Suraparaju <anuradha@hoyle.rd.bbc.co.uk>

Date: Fri, 17 Apr 2009 17:47:27 +1000

Subject: [PATCH] Fix uninitialised memory read that causes the encoder to crash when using

 non-overlapping blocks.

---

 libdirac_common/mot_comp.cpp |   21 +++++++++++++++------

 1 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/libdirac_common/mot_comp.cpp b/libdirac_common/mot_comp.cpp

index aa8d37c..e0ec2ff 100644

--- a/libdirac_common/mot_comp.cpp

+++ b/libdirac_common/mot_comp.cpp

@@ -306,6 +306,8 @@ void MotionCompensator::CompensateComponent( Picture* pic ,

     int save_from_row = m_bparams.Ybsep()-m_bparams.Yoffset();

+    bool row_overlap = ((m_bparams.Yblen() - m_bparams.Ybsep()) > 0);

+

     // unpadded picture dimensions

     const int x_end_data = pic_data_out.FirstX() + std::min(pic_data_out.LengthX(), pic_size.x );

     const int y_end_data = pic_data_out.FirstY() + std::min(pic_data_out.LengthY(), pic_size.y );

@@ -489,12 +491,19 @@ void MotionCompensator::CompensateComponent( Picture* pic ,

         //Increment the block vertical position

         pos.y += m_bparams.Ybsep();

-        // Copy the rows required to motion compensate the next row of block.

-        // This is usually Yblen-Ybsep rows.

-        memmove (pic_data[0], pic_data[save_from_row], (m_bparams.Yblen() - save_from_row)*pic_data.LengthX()*sizeof(ValueType));

-        memset( pic_data[m_bparams.Yblen() - save_from_row], 0, save_from_row*pic_data.LengthX()*sizeof(ValueType) );

-        save_from_row = m_bparams.Ybsep();

-

+        if (row_overlap)

+        {

+            // Copy the rows required to motion compensate the next row of 

+            // blocks. This is usually Yblen-Ybsep rows.

+            memmove (pic_data[0], pic_data[save_from_row], (m_bparams.Yblen() - save_from_row)*pic_data.LengthX()*sizeof(ValueType));

+            memset( pic_data[m_bparams.Yblen() - save_from_row], 0, save_from_row*pic_data.LengthX()*sizeof(ValueType) );

+            save_from_row = m_bparams.Ybsep();

+        }

+        else

+        {

+            // no row overlap. So reset pic_data to 0.

+            memset( pic_data[0], 0,  m_bparams.Yblen()*pic_data.LengthX()*sizeof(ValueType) );

+        }

     }//yblock

     if ( m_add_or_sub == SUBTRACT)

-- 

1.7.0.3