fix error in equation variables

042_ConcealmentAwareEncoding/ConcealmentAwareEncoding.tex

@@ -354,7 +354,7 @@ where $R(m_{l,i})$ represents the number of overhead bits required to encode the
 
 
 In equation~\ref{EQ6:OptimalDepth}, besides the parameter $\lambda$, used to  trade-off distortion and overhead rate in the minimisation process, there is also a weighting factor to control the cost of $R(m_{l,i})$, according to the duration of the error propagation.
-As in the method proposed in the Chapter~\ref{Chapter:ErrorResilienceTechniques}, this method uses the ratio between the temporal distance from the current frame ($t_C$) to the next refresh frame ($t_I$) and the period of refreshing frames ($T_{I}$).
+As in the method proposed in the Chapter~\ref{Chapter:ErrorResilienceTechniques}, this method uses the ratio between the temporal distance from the current frame ($t_C$) to the \HIGHLIGHT{previous refresh frame} ($t_I$) and the period of refreshing frames ($T_{I}$).
 %This weight varies between $\left[0;1 \right]$, achieving the lowest value for  intra-coded frames and the maximum  for the frame located immediately before an intra-coded one.
 This behaviour follows the fact that when a lost frame is closer to the next intra-coded frame, the error propagation is lower. 
 Thus, it is not worthwhile to spend too many overhead bits to reduce it. This is accomplished by increasing the cost of such bits according to the temporal distance between the missing frame and the next I frame.