Switching Between HDTV and SDTV (Engineering Question)

[Markxxx]

The thought of having two networks affiliates on on subchannels got me thinking.

Let's say you have a station and it carries CBS on the main channel and FOX on the subchannel.

Now obviously sports are one thing that definitely looks better in HDTV.

How hard is it for a TV station to switch? So let's say CBS had a sitcom on while FOX was going to carry football.

Would it be hard for the TV station to switch over and carry the CBS sitcom in SDTV and change to HDTV for the football on FOX?

I am asking from a technical standpoint, not necessarily something networks would agree to

Thanks

 

[Bill_W]

The thought of having two networks affiliates on on subchannels got me thinking.

Let's say you have a station and it carries CBS on the main channel and FOX on the subchannel.

Now obviously sports are one thing that definitely looks better in HDTV.

How hard is it for a TV station to switch? So let's say CBS had a sitcom on while FOX was going to carry football.

Would it be hard for the TV station to switch over and carry the CBS sitcom in SDTV and change to HDTV for the football on FOX?

I am asking from a technical standpoint, not necessarily something networks would agree to

Thanks

You could run both in 720p couldn't you? WPVI in Philly is doing it.

 

[tripinva]

The bigger problem with it is that there are some TVs that just don't handle it well, either going to black when the format changes, or having a huge glitch of some kind.

For example, stations used to switch between stereo and 5.1 for their audio, until they realized that a number of receivers were creating very loud glitch sounds when they did it. Nowadays, most stations stay in 5.1 mode all the time while feeding just left and right or simulating a 5.1 mix.

- Trip

 

[anotherguyTN]

The thought of having two networks affiliates on on subchannels got me thinking.

Let's say you have a station and it carries CBS on the main channel and FOX on the subchannel.

Now obviously sports are one thing that definitely looks better in HDTV.

How hard is it for a TV station to switch? So let's say CBS had a sitcom on while FOX was going to carry football.

Would it be hard for the TV station to switch over and carry the CBS sitcom in SDTV and change to HDTV for the football on FOX?

I am asking from a technical standpoint, not necessarily something networks would agree to

Thanks

You could run both in 720p couldn't you? WPVI in Philly is doing it.

It makes more sense than what WBBJ in Jackson, TN is doing. They're running ABC in 720p and CBS in 480i.

 

[nomadcowatbk]

The bigger problem with it is that there are some TVs that just don't handle it well, either going to black when the format changes, or having a huge glitch of some kind.

For example, stations used to switch between stereo and 5.1 for their audio, until they realized that a number of receivers were creating very loud glitch sounds when they did it. Nowadays, most stations stay in 5.1 mode all the time while feeding just left and right or simulating a 5.1 mix.

- Trip

WDAF broadcasts Fox programming in 5.1, but local programming in just in stereo

 

[w9wi]

The bigger problem with it is that there are some TVs that just don't handle it well, either going to black when the format changes, or having a huge glitch of some kind.

For example, stations used to switch between stereo and 5.1 for their audio, until they realized that a number of receivers were creating very loud glitch sounds when they did it. Nowadays, most stations stay in 5.1 mode all the time while feeding just left and right or simulating a 5.1 mix.

- Trip

Yep, switching modes has proven not a very good idea. It's also somewhat difficult for the infrastructure.

A better shot is something called "statistical multiplexing". Instead of splitting the 19.39Mbps 50/50, giving each program ~9.7Mbps -- you give more bandwidth to the program that needs it. Maybe when someone's running down the field you give Fox 16M & CBS 3M -- when the guy on Fox scores the TD & they put up the still frame with his stats, you give Fox 6M and CBS 13M. Etc...

Trip, IIRC your site denotes (in the screengrabs) whether a station has a statmux?

 

[tripinva]

It notes whether or not a station has a variable bitrate. Some stations have variable bitrate without stat muxing, and it can be difficult to tell them apart in cases where I'm given just the TSReader HTML document which it is, so I settled on just listing constant or variable.

- Trip