American Broadcast Networks and Affiliates

Thanks to forums like this one I’ve learnt a lot about past and present networking and playout arrangements in the UK. Media Spy is an Australian forum and from there I have gained equally fascinating information about how things work, and worked, in Australia. However, I know very little about the over-the-air networks in the USA - NBC, CBS, ABC et al.

The American networks differ from the UK and Australia in many ways, not least that there is no fully-scheduled network feed - the networks generally only provide national news, a breakfast show, a few daytime soaps or talk shows, three hours of prime-time entertainment, perhaps a late night talk show and weekend morning shows for kids. Much of the schedule is provided by the affiliate in each market - local news and locally produced content and syndicated shows they buy in - putting things simply.

With there being various time zones in the USA, there used to be an East Coast and West Coast feed - the West feed being delayed into those markets - and the Central time zone receiving the East Coast feed live (but appearing to be scheduled an hour earlier eg. 8pm East, 7pm Central). I think the Mountain time zone received the West Coast feed in a similar way. Nowadays I don’t know if the feed is still delayed or if everything is played out more than once (as it’s much easier to do so now that tapes are not involved).

Some ads are networked and others are local - and some stations choose to move daytime shows around, showing them at a different time to the “network”. In cases like these, I don’t know if it’s up to the station to record the show down the line and play it back, or if the network feeds those shows to that market(s) at the appropriate time. As for playout in general, is it still mainly done in-house at each affiliate?

I assume each network has its own playout centre - but I’m not sure if this is independent of any station, or if they have an O&O home/flagship station in say NYC or LA that is responsible for originating the sustaining/clean feed for all other markets? Or is playout actually outsourced, as it often is in the UK and Australia?

Any information would be welcome!

I know in the case of FOX, they use (or maybe used to use) some clever satellite kit at the affiliates for the network feed.

The network feed with programmes and adverts came over satellite pre-encoded (as MPEG2 720p60 at around 13Mbps, ready for transmission via the ATSC DTT system). The satellite kit at the affiliate would receive this stream and use flags within it to know when to apply the local DOG or cut from network to local input.

The most interesting bit is that the graphics/DOG got loaded into the kit as an image, and then got applied to the pre-encoded satellite MPEG2 stream by just re-encoding that small part of the picture to add it, leaving the rest as-is!

Presumably this equipment also dealt/deals with encoding the local input to the same specification as the incoming satellite feed.

Insertion etc is to SCTE 35
https://scte-cms-resource-storage.s3.amazonaws.com/ANSI_SCTE-35-2019a-1582645390859.pdf

The logo inserter is a little bit difficult to explain but was done as a product about 25 years ago by Snell &Willcox ... in simple terms you define the macroblocks you are going to alter and recode those blocks with a logo,added and insert these new packets in the stream .
This was done by a decode add logo encode on these macro blocks ( delaying the rest of the stream to allow the GOP or two that this took )
but these days a partial decode / inspection of the macro block data and then a alteration to it added to the stream .... this has a lot less delay but a lot of processing power....