You asked: “I wonder if there is a single device that accepts mic audio as input and outputs S/PDIF stream?” Besides, what will the SPDIF input be used for, you mention microphone as input but no analogue device for output.
I was unclear in the first post, sorry. The objectif is full duplex over some custom channel, i.e. something like this:
(1) MIC (digital or analog) ->MIC AFE (if analog) ->CODEC-> line driver -------- channel ---------> (2) line receiver->CODEC->DAC ->AMP->Speaker
(1) Speaker <- AMP <- DAC<- CODEC <- line reciever <----------- channel ------------ (2) line driver <- CODEC <- MIC AFE (if analog) <- MIC (digital or analog)
(1) device 1, (2): device 2.
As for the generic term CODEC, it can be either a device that outputs S/PDIF or a serializer/deserializer device that receives I2S as input and provides a serialized single line stream (for the serializer ) or a deserialized single line stream in a 3-signal I2S bus (for the deserializer) ... e.g. MAX9205/MAX9206.
In the case of S/PDIF, the candidats are PCM3052A, PCM2903CDB, PCM9211, LMV1012, pair (DIT4096, DIR9001), ADAU1452, D2-6 Family Audio SOC (from Renesas).
According to my research so far, the most cost-optimal solution seems to be using the pair (DIT4096, DIR9001).