This is an open letter to the ADV7842 design team.
I was not able to get any output on AP1 in the I2S format with a compressed audio signal (Dolby Digital) coming in over HDMI. Every status indicator showed that it should be working and that audio was unmuted. I tried playing with I2SOUTMODE and finally found some activity on the pin when I set it to RAW SPDIF. But the SPDIF signal didn't look right so I set it back to I2S mode and just for the heck of it I tried setting bit 7 of the register (HDMI Map 0x03). Lo and behold I got the correct I2S output!
Bit 7 in this register is not documented in the HW reference manual or the register map. This register is not written to in any of the HDMI scripts. Needless to say I am really pissed off about the lack of documentation, having wasted several days trying to get it to work. This is such a basic operation for this part, most cable channels use Dolby Digital for their audio, that I can't believe this wouldn't have been tested and documented properly.