A double data rate serial encoder is provided. The serial encoder comprises a mux having a plurality of inputs, a plurality of latches coupled to the inputs of the mux, an enabler to enable the latches to update their data inputs, and a counter to select one of the plurality of inputs of the mux for output. In another aspect, the mux provides a glitch-less output during input transitions. The mux includes an output selection algorithm optimized based on a priori knowledge of an input selection sequence provided by the counter.