X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/canny.git/blobdiff_plain/3cb99fa4936f62fef8a0f24880e7d9bca9c31a9e..3d3a92a59f998403d73c474b6565a18b3c248dec:/stc.tex diff --git a/stc.tex b/stc.tex index f87104b..26ac732 100644 --- a/stc.tex +++ b/stc.tex @@ -1,5 +1,5 @@ To make this article self-contained, this section recalls -basis of the Syndrome Treillis Codes (STC). +the basis of the Syndrome Treillis Codes (STC). Let $x=(x_1,\ldots,x_n)$ be the $n$-bits cover vector of the image $X$, $m$ be the message to embed, and @@ -19,7 +19,7 @@ Furthermore this code provides a vector $y$ s.t. $Hy$ is equal to $m$ for a given binary matrix $H$. Let us explain this embedding on a small illustrative example where -$\rho_X(i,x,y)$ is identically equal to 1, +$\rho_X(i,x,y)$ is equal to 1, whereas $m$ and $x$ are respectively a 3 bits column vector and a 7 bits column vector. Let then $H$ be the binary Hamming matrix @@ -68,12 +68,12 @@ is a practical solution to this complexity. Thanks to this contribution, the solving algorithm has a linear complexity with respect to $n$. First of all, Filler \emph{et al.} compute the matrix $H$ -by placing a small sub-matrix $\hat{H}$ of size $h × w$ next -to each other and shifted down by one row. +by placing a small sub-matrix $\hat{H}$ next +to each other and by shifting down by one row. Thanks to this special form of $H$, one can represent -every solution of $m=Hy$ as a path through a trellis. +any solution of $m=Hy$ as a path through a trellis. -Next, the process of finding $y$ consists of two stages: a forward and a backward part. +Next, the process of finding $y$ consists in two stages: a forward and a backward part. \begin{enumerate} \item Forward construction of the trellis that depends on $\hat{H}$, on $x$, on $m$, and on $\rho$. \item Backward determination of $y$ that minimizes $D$, starting with