int32.positive trkIdx
int32.positive stepIdx
int32.positive valueIdx
frac32 stepValue
objref seq
uint32_t valueIdx = inlet_valueIdx < attr_seq.numValues_
? inlet_valueIdx
: attr_seq.numValues_ - 1;
outlet_stepValue = attr_seq.seqValue_[inlet_trkIdx][inlet_stepIdx][valueIdx];