On 10/10/2007, Martin Deutsch <[EMAIL PROTECTED]> wrote: > Switching between SDI signals is easy; what Duncan's suggesting is a bit > trickier. > At present: the BBC and ITV, and Channel 4 have satellite multiplexes which > carry several channels which are the same for most of the day; they can > differ when it comes to news, regional programmes and advertising. Ideally, > each mux could carry a high bitrate version of (eg) ITV1 during network > programming, but during regional opts (local news, ad breaks, etc), would > carry each of the local streams, though probably at a lower bitrate, and the > viewer wouldn't notice a thing. > I *think* that DVB can do this, but changing the SI tables (which tell the > receiver where to find the video and audio associated with a network) on the > fly isn't an exact enough science to be able to do it with the frame > accuracy desired by the broadcasters > > I suspect someone - BBC R&D? - has already done research into this. > > - martin >
Yes that is what I was getting onto, wasn't sure about going into broadcast acronyms too much was half my issue before. If it were possible then it would free up an awful lot of bandwidth for a higher quality ITV1 (for example) during non-regional times, I'd love it to be possible, on Sky there are three multiplexes dedicated to ITV feeds so there is quite a lot to be potentially saved. The switching your talking about is half the issue, its also the fact that you can only really cut from one stream to another roughly once every 12 frames due to the nature of MPEG, hence why set-top boxes stop for a sec when you change channel. This gives you a very tight window if you want to do a seamless switch and would also be dependent on the set-top boxes ability to traverse the SI table in that time. Perhaps it is possible, I haven't seen anything from BBC R&D about it (but then again the BBC management is reportedly flushing that away like everything else of worth from the old corporation) and it would be interesting to try it, assuming I can't find any reason not to, I will try to scavenge enough equipment/rack space to run a little test at some stage. - Sent via the backstage.bbc.co.uk discussion group. To unsubscribe, please visit http://backstage.bbc.co.uk/archives/2005/01/mailing_list.html. Unofficial list archive: http://www.mail-archive.com/[email protected]/
