Two dimensional data compression of speech

Speech signal is considered as a two dimensional pseudo-image by segmenting it into blocks of N sample points. Successive segments are placed adjacently thereby forming a sequence of columns or a two dimensional image. Image data compression techniques can now be applied to exploit inter-segment redundancies. We present a hybrid coding scheme for speech. Each segment is first unitarily transformed. This is followed by a DPCM which operates on each of the N transformed samples from one segment to the next. Thus, we perform transform coding in one dimension and DPCM in the other. Results on a 30 second long conversation are presented.