Wavelet transcoding in the block discrete cosine transform space

Transcoding in the transform domain avoids inverse transform and re-transform computations. In this paper, discrete cosine transform, the authors propose a new technique for transcoding wavelet coefficients to block discrete cosine transform (DCT) coefficients in the transform domain. In the first step, wavelet coefficients are transformed into upsampled DCT blocks. Subsequently, these transformed blocks are synthesised by filtering in the block DCT space. To reduce the cost of transcoding, the authors perform upsampling and filtering operations in a single combined step. The proposed technique achieves the quality of reconstruction (except rounding errors in processing) as same as the spatial domain technique with reduced complexity for a given wavelet synthesis filter. The proposed technique is based on simple linear operations like matrix multiplication. This makes the algorithm more convenient for efficient hardware implementations. The technique can be used by the DCT-based services when the input data are available as wavelet coefficients.