Not labelled, no, they are: (pin 1 is indicated by a sloped corner on the bounding box)

1 - I2S clock (1.4112MHz)
2 - I2S word select (44.1kHz)
3 - Ground
4 - I2S data 1 (front L/R channel)
5 - I2S data 2 (rear L/R channel)

Next to this is the 2 pin I2S power header. Both pins are connected to the empeg 3.3v supply line.

The DSP can be programmed so that the digital outputs give other things - eg, ISTR there's a subwoofer filter/centre channel, which would allow you ot have the normal 4ch empeg output, plus add an external DAC to give you sub/centre out.

Sub is just something like a 5th order programmable lowpass, centre is just a mix of front L/R.

Hugo