I2S or Sony format signal separator and repeater?

Mono application of the AD1853 requires to repeat and invert the left resp. right channel signals. Anybody got an idea how to do this without using 4 pieces 8 bit shift registers and a lot of support logic? Preferably, it should be possible to adjust this to various formats, i.e. I2S and Sony right justified, 16-24 bits, 16 - 64 bit clocks per word.

Thanks

Eric