Digging through the various edid info I've collected from 4 TVs.
Attempting to send CEA format 4 (720p). Chip reports detected VIC of 4 and sent to rx of 4. I double checked the CEA spec to ensure my vsync/hsync pulses and offsets were being generated correctly.
Working;
ViewSonic Monitor: Year 2014. Has 720p listed in dtds with Exact CEA format 4 specs.
Westinghouse TV: Year 2013. Has 1080i/1080p But doesn't list VIC4.. Instead it lists VIC 19 (720p at 50Hz). Regardless it still worked with I sent it format 4.
Not working:
Vizio TV: Year 2006. Has VIC 4 in edid. Also supports 1080i
Sylvania TV: Year 2010: Has VIC 4 in edid. Supports lots of other resolutions ]
In all cases the registers on the ADV7511W report vic 4 detected and vic 4 sent to Rx. I've also tried with 1080i and 720x480p. The result is always the same. The TVs that work work and the two that don't work don't show anything at all on the screen. On the ones that don't work it's like they simply don't even detect a signal. At least on the TVs that work if I change refresh rate or something to not supported I'll get an out of scan range message or other appropriate info. The non-working TVs act like the cable isn't even plugged in.