From: Brian Butterworth > On DVB-T it is everything. BBC One used to have reserved bandwidth, but is > now statmuxed with everything else. My assumption is the BBC delivers > motion-JPEG to the regional encoders and the services are statmuxed from > there.
Don't know the gory technical details, however in areas which have undergone digital switchover, the opt outs are now sent from the National and Regional centres down the pipes to the Central Coding and Mux in London, then encoded with the rest of the mux and sent back up the relevant transmitters. I presume areas which are awaiting digital switchover are still using the previous method whereby opt outs are inserted at the national and regional centres as you say (have absolutely no idea about formats used)