ITU-T Recommendations

Appendix IV defines a coding scheme for mid-side (MS) stereo using ITU-T G.711.1 Annex D (G.711.1-SWB). By introducing the mid-side stereo coding into stereo terminals, interoperability with the monaural devices could be obtained in very low complexity.The basic coding scheme is as follows;a) Two channels of the left-right (LR) stereo are converted to those of the MS stereo and then the signals of each channel are independently encoded using G.711.1-SWB,b) At the decoder side, the MS channels of the bitstream from the encoder are decoded respectively and then the decoded signals of the MS channels are reversed to those of the LR channels.The LR-MS conversion and its inverse are conducted in a conventional way. On the encoder side, additional two arithmetic operations per sample are required for the LR-MS conversion and one operator for the MS-LR conversion in the decoder. In an STL2009 [b-ITU-T G.191] basic operator implementation, the conversion complexity amounts to about 0.2 WMOPS in total. The coding algorithm for each channel is identical to the one in ITU-T G.711.1 Annex D