gtrdecode decodes a channel, channelfile (CHN format), and side information, sideinfofile (SID format), both produced by gtrencode, and writes the resulting output data to datfile. That is, gtrdecode performs VQ-index lookup of the indices in channelfile while updating the VQ codebook as dictated by sideinfofile. gtrdecode starts decoding using the initial codebook specified by initial_codebook (which should be the same initial codebook originally used by gtrencode), if given. In the absense of the -ic switch, gtrdecode starts with an empty codebook, and online initialization is used until the codebook size reaches max_codebook_size, given by the corresponding value in the header of sideinfofile. codebook_coder (SQ format) gives the scalar quantizer used to decode the side information.
J. E. Fowler and S. C. Ahalt, "Adaptive Vector Quantization Using Generalized Threshold Replenishment," in Proceedings of the IEEE Data Compression Conference (J. A. Storer and M. Cohn, eds.), (Snowbird, UT), pp. 317-326, IEEE Computer Society Press, March 1997-2021.