sptbl["butlp"] = {     files = {        module = "butlp.c",        header = "butlp.h",        example = "ex_butlp.c",    },     func = {        create = "sp_butlp_create",        destroy = "sp_butlp_destroy",        init = "sp_butlp_init",        compute = "sp_butlp_compute",    },     params = {        optional = {            {                name = "freq",                type = "SPFLOAT",                description = "Cutoff Frequency.",                default = 1000            },        }    },     modtype = "module",     description = [[Lowpass Butterworth filter]],     ninputs = 1,    noutputs = 1,     inputs = {        {            name = "input",            description = "Signal input."        },    },     outputs = {        {            name = "output",            description = "Signal output."        },    } }