  This paper introduces a collection of scaling methods for generating
$2N$-point DCT-II approximations based on $N$-point low-complexity
transformations. Such scaling is based on the Hou recursive matrix
factorization of the exact $2N$-point DCT-II matrix. Encompassing the widely
employed Jridi-Alfalou-Meher scaling method, the proposed techniques are shown
to produce DCT-II approximations that outperform the transforms resulting from
the JAM scaling method according to total error energy and mean squared error.
Orthogonality conditions are derived and an extensive error analysis based on
statistical simulation demonstrates the good performance of the introduced
scaling methods. A hardware implementation is also provided demonstrating the
competitiveness of the proposed methods when compared to the JAM scaling
method.
