Accordingly to the AD1939 datasheet the default mode for this device is I2S.
In this case, should we consider that only two channels of the device are used ? Only one Left and one Right ADC and only one Left and one Right DAC ?
There is a dedicated data pin for each stereo pair of DAC's.  So the LRCK and BCLK would be applied, and the data would be applied at the data pin corresponding to the desired pair of DAC's.
Thank you for your answer.
The I2S format support only two channels. The AD1939 has 8 channels. What happens with the rest of 6 channels in case of using I2S format ?