You cannot apply this “single channel mixer” directly in the context of the TDM mixer. Samples arrive from different channels in an interleaved manner, yet they arrive consecutively in the single channel case. You have a data flow problem: you must convert your interleaved stream into a channel-by-channel stream at the mixer input and then restore its interleaved format at the mixer output. This operation is sometimes called a “corner-turn” or “2D transpose” operation based on the figure shown below. Samples arrive row-wise interleaved by channel, one sample at a time. The diagram shows four channels and eight samples for each channel. The “single channel mixer” should then be fed with samples chosen column-wise, first 8 samples from channel 0, then eight samples from channel 1, and so on. The minimum # of samples must be eight to match the vectorization. In practice, the column depth will be some multiple of eight.