The sig finder match I added last night says the video detect bit should be 0x00800000 in word 0 for this camera.
The bit could be in one of the varying digits, in that case the changing values should be different with/without the cable, e.g. it might cycle 1, 5 without the cable and 9, d with.
If the sig finder is correct then I should probably have just bought some toothpicks.
With no cable, the 3rd nibble (of word 0) includes 2 & a. However, it includes 2 with the cable connected.
I had (somehow) initially suspected a bit of the 5th nibble ... with no cable it included 1 & 5 while the first occurrence of that with cable connected was d. However, a second test with cable attached had that return 1.
Anyway, only if the sig finder is incorrect does there seem any purpose to analyze other changes but I wouldn't then be sure how to pin the bit down.
Screenshot and spreadsheet of results attached.