Originally Posted by SimonBlackham:
“The BBC say that Freeview and Freesat are unconnected - but contrary to this they seem to be kept logistically the same - hence the change to 1920 will (should?) be on both and will have to return to 1440 because of the bandwidth limitations on Freeview.”
The only explanation is that either there is already enough headroom for one 3D channel on both Freeview and Freesat, or bitrate from another channel has to be robbed for the 3D/HD channel.
I suspect the first because in the case of Freeview the capacity has to come from a 40Mbps mux already running four streams with an unknown (to me) null packet rate. Freesat has a vacant fourth HD stream so has plenty of bitrate available.
If more bitrate is required, in the case of Freeview, the only source of more capacity is BBC One HD or any null packets available or perhaps cutting data or audio streams like ALBA in Scotland.
In the case of Freesat there is plenty of unused capacity. But why would the BBC implement a different solution for DTT and satellite when both platforms have 4 HD stream capability out of a 40mbps transport stream? The conversion to S2 would allow the BBC to run an HD interactive red button channel for Wimbledon as well as a 3D trial before using it for other purposes.