NAME

       ms_genfactmult - Generate SEED sample rate factor and multiplier

SYNOPSIS

       #include <libmseed.h>

       int  ms_genfactmult ( double samprate, int16_t *factor,
                             int16_t *multiplier );

       int  ms_ratapprox ( double real, int *num, int *den,
                           int maxval, double precision );

DESCRIPTION

       ms_genfactmult  generates  an  appropriate  SEED  sample  rate  factor  and multiplier pair from a double
       precision sample rate.  If samprate is positive it is expected to represent a rate in samples/second,  if
       negative is is expected to represent a period in seconds/sample.

       Non-integer  sample  rates  and  periods  are  supported between 32767.0 and 1/32767.0.  An error will be
       returned for non-integer rates and periods outside this range.

       Integer sample rates and periods are supported between 1 and the maximum possible value (32767 *  32767).
       Values  from  1 to 32767 are represented directly.  Values larger than 32767 are factored and represented
       exactly when possible and approximated otherwise, with the discrepency  becoming  larger  as  the  values
       reach the maximum possible value.

       The  factor  and  multiplier are int16_t because that is the integer size needed for the fixed section of
       the SEED data header.

       ms_ratapprox finds an approximate rational number for a real through continued fraction expansion.  Given
       a  double  precision  real  the routine tries to find a rational in numerator (num) and denominator (den)
       form whose absolute values are not larger than maxval while trying to reach a specified precision.

RETURN VALUES

       ms_genfactmult returns 0 on success and -1 when value is outside of the supported range or error.

       ms_ratapprox returns the number of iterations performed.

AUTHOR

       Chad Trabant
       IRIS Data Management Center