There were a few cable cam rigs, the most impressive was strung between two 300ft towers, 2.5km apart for the rowing.
The cable broke but was replaced without too much hassle.
Over 30 stabilised cameras in use in London.
The 3d TV broadcast transmission had an open mic of the arena, the sound of a helicopter was quite prominant, sounded like a AS355. Pity the organisers were not moved to have an EC 135 in the fleet.
Something to consider for Rio?
Here is a DIY cablecam system which wasn't in use during the olympics, love the use of mark I stabilised system
Mickjoebill