Image coding with incomplete transforms competition for HEVC

Overcomplete transforms have received considerable attention over the past years. However, they often suffer from a complexity burden. In this paper, a low complexity approach is provided, where an orthonormal basis is complemented with a set of incomplete transforms: those incomplete transforms include a reduced number of basis vectors that allow a reduction on the coding complexity and ensure a certain level of sparsity. The solution has been implemented in the HEVC standard and compression gains of around 1% on average are reported while reducing the decoder complexity in about 5%.