A composite input signal having an audio component and a video component is routed from an input to an output by separating a stream of audio data words at an average frequency F1 from the video component and supplying the separated stream of audio data words sequentially to a FIFO input register. The output of the FIFO input register is polled at a frequency F2, greater than F1, and, in the event that an audio data word is available at the output of the FIFO input register, the audio data word is conveyed from the output of the FIFO input register to an input of a signal path. Otherwise a null data word is conveyed to the input of the signal path. The signal path thereby conveys a stream of data words that comprises both audio data words and null data words. The audio data words of the stream conveyed by the path are combined with the video component of the composite input signal.