WBZ time tone

[Ed101]

I'm curious... why is the WBZ time tone at the top of the hour always precisely 9 seconds late? ???

 

[jlehmann]

It's late because of the extra delay caused by having HD Radio.

 

[WLYNWAZNgm]

Possibly (more likely) they are running a digital delay,
so as to have that extra measure of protection, to guard against
bad language, etc., that could slip out. With some stations
being hit with big punitive fines, better to be extra careful...

 

[jlehmann]

The delay to prevent curses from making the air would probably cause it to be much later than just 9 seconds, if that was the cause. I believe the time tone has only been late since they started running HD.

 

[WLYNWAZNgm]

I beg to differ. A delay of 8-9 seconds is an industry standard for
obscenity prevention. If it is a digital delay, the system will build
up the cache of 8-9 seconds built up from pauses in the program, starting at
zero seconds delay, after a call has been dumped. I cannot see a situation that
an HD broadcast, transmitted in real time, would inherently require any delay at all.
Can any of you engineering types confirm or deny that?

 

[rockcaptain]

I beg to differ. A delay of 8-9 seconds is an industry standard for
obscenity prevention. If it is a digital delay, the system will build
up the cache of 8-9 seconds built up from pauses in the program, starting at
zero seconds delay, after a call has been dumped. I cannot see a situation that
an HD broadcast, transmitted in real time, would inherently require any delay at all.
Can any of you engineering types confirm or deny that?

In order for there to be a seemless transition once the HD signal locks in, the analog signal is delayed. The HD encoding results in a delay in the HD audio. The delay of the analog signal allows for seemless transition of HD and analog. At one time (not sure if there still is) there were some stations in Boston that did not implement a proper delay. So, once the HD locked in, you heard the same programming you already heard on the analog signal.

 

[jlehmann]

Right now, all stations seem to be properly delaying their audio. WBCN shuts off their during Patriots home games, probably so fans in the stadium can listen to the game live on portable radios.

WBZ must insert their time tone separately from the main audio chain, which would be delayed during talk shows. I'm sure someone else can back me up here and say that the tone has only been delayed since they installed HD.

 

[WLYNWAZNgm]

I remain unconvinced. If that were the case, why wouldn't they just start the
HD stream 8-9 seconds before it is intended to air?

 

[Ed101]

Of course I understand the profanity delay ;D ... but with or without HD, it has to be possible to insert a tone later in the air chain, and start it early, so it airs on time.

 

[oldiesfan6479]

Based on all the threads/postings about WBZ and KDKA's
first adjacent hash banging against each other's primary
freq., along with 'BZ hash stomping all over WYSL 1040
Avon NY (near Rochester), it's the I-CRAP.

"Save AM radio...kill I-CRAP"

 

[rockcaptain]

I remain unconvinced. If that were the case, why wouldn't they just start the
HD stream 8-9 seconds before it is intended to air?

HD encoding and broadcasting is not always simple to understand. But once you have an understanding of how it works, it is quite obvious. Let's use live/analog as the benchmark. You talk and it is sent through the broadcast chain. Without a digital obscenity delay, your voice is almost instantaneously sent over the air (in an analog scenario). Now, let's add HD into the mix. Digital encoding causes a delay. In order for the analog and HD audio to match up (because of the transitions that occur as the HD signal is acquired and lost on occasion), you need to delay the analog signal that is sent out. You can't start the "HD stream" before the analog has begun...that's like going back in time. If you did not delay the analog signal you would have a mis-match of audio between the analog and HD which really messes things up. Some stations out there operate like that but the analog is ahead of the HD (which how it has to be because the HD gets delayed because of the encoding). That is why they delay the analog so the HD will match up.

 

[jlehmann]

I remain unconvinced. If that were the case, why wouldn't they just start the
HD stream 8-9 seconds before it is intended to air?

That would be impossible. How are you going to be able to broadcast what someone said 8 seconds ago before the transmitter is turned on? HD Radio cannot be broadcast in real time, and it's because of buffering, similar to internet streams. I believe this is done so the signal would not cut out instantly when driving under every underpass, set of power lines, etc, as the listener drives around.

 

[rockcaptain]

Of course I understand the profanity delay ;D ... but with or without HD, it has to be possible to insert a tone later in the air chain, and start it early, so it airs on time.

They can even insert the tone as normal (not later in the chain). They just need to compensate for the fact that there is a delay over the air. Set the clocks back a few seconds in the studio (this is actually done at many stations). This would create a problem when picking up live satellite feeds though.

 

[rockcaptain]

I remain unconvinced. If that were the case, why wouldn't they just start the
HD stream 8-9 seconds before it is intended to air?

That would be impossible. How are you going to be able to broadcast what someone said 8 seconds ago before the transmitter is turned on? HD Radio cannot be broadcast in real time, and it's because of buffering, similar to internet streams. I believe this is done so the signal would not cut out instantly when driving under every underpass, set of power lines, etc, as the listener drives around.

You are absolutely correct. When you turn on an HD receiver the analog signal is picked up first. Then the receiver will attempt to acquire the HD signal. Once the HD is locked in, there is a smooth transition. If the HD is lost, the receiver will smoothly transition back to the analog.

 

[Erie_Lackawanna]

what if the station were to use a flux capacitor that operated properly at 1.21 gigawatts while broadcasting at 88 mph? just wonderin'

 

[fybush]

Of course I understand the profanity delay ;D ... but with or without HD, it has to be possible to insert a tone later in the air chain, and start it early, so it airs on time.

They can even insert the tone as normal (not later in the chain). They just need to compensate for the fact that there is a delay over the air. Set the clocks back a few seconds in the studio (this is actually done at many stations). This would create a problem when picking up live satellite feeds though.

Correct - and with all the network feeds WBZ has to meet at fixed times (CBS 31:00 updates at the bottom of the hour, TOH hourly news overnight, etc., resetting the studio clocks a few seconds would be a massive headache.

That said, it IS possible to insert the time tone separately to the analog and digital feeds. I believe WTIC in Hartford is doing that, but I forget the details.

There is no profanity delay operating during WBZ all-news programming; there is, of course, during the talk shows starting at 8 PM.

 

[DanStrassberg]

I remain unconvinced. If that were the case, why wouldn't they just start the
HD stream 8-9 seconds before it is intended to air?

It takes A LOT of computer manipulations, AKA DSP (digital signal processing), to convert the analog signal that comes out of microphones and network feeds into the multiple OFDM (orthogonal frequency-division multiplexed) carriers that create those annoying sidebands that sound like white noise on either side of the analog signal of an AM station that is broadcasting IBOC. Creating the OFDM stream is a much more complex operation than "mere" analog to digital conversion, which nowadays can be done in nanoseconds. Despite chips that perform billions of operations per second, the processing takes time (AKA pipeline delay) and the pipeline delay for the AM-band HD Radio system is ~8 sec. For the signal to gracefully blend back to analog in the event that the receiver loses the digital signal (easy for that to happen), the analog modulation must be delayed by an identical amount.

Now, you may ask why WBZ doesn't simply advance the content by 8 sec. They can't because of the network feeds. Could they advance just the hourly time tone? Yes, but if you think about the implications of doing that, I think you will agree that it's probably better to let the audio come out eight seconds late.