Echo! Echo! Echo!

[vchimpanzee]

I was watching a program on the TV with converter box no. 1. While I've never done this, apparently I could hear the sound three different times if I could stand in the right place. All I know is I've stood where I could hear a slight delay between the sound from the TV with the converter box and the sound from the same channel on cable, and I've stood where I could hear a slight delay between the sound coming from a TV simply hooked up to cable and the TV hooked up to TiVo. I tried putting all three TVs on the same show but I couldn't hear all three at once. I just know standing between the first two I heard a delay, and between the second two I heard a delay.


People complain about the delay to prevent profanity, so this means it might not work to listen to a sports event on the radio if you're watching on cable. Especially if you have TiVo.

 

[Studio20]

Was there a little blond girl in the room who uttered the phrase "They're here."?

 

[vchimpanzee]

Come now. Someone ought to be able to say whether this is real. It's obvious that there is some delay on Tivo because both stations are hooked up to the same cable.

As for over-the-air TV, I did say I was watching the same station, but I wasn't. Just an affiliate of the same network.

 

[DToTheJ]

You call it echo; I just call it stereo.

 

[Darth_vader]

When the "Golden Hours" radio reading service was still being transmitted via KOPB's SAP, I would often listen to it on my pre-2000 Panasonic PV-9662 VCR. In later years I purchased a radio receiver with an SCA/SAP demodulator which allowed me to hear it when i wasn't within reach of my stereo. The VCR isn't exactly a "software-defined" tuner (not like my DMR-EZ27) but there was still some very slight processing delay.

It was enough, however, to make tuning the radio and VCR both to KOPB's SAP, provide a rather odd "concert hall" effect during the news readings. ;o)

[size=8pt](Epilogue: Oddly enough, the VCR never seemed to have that behaviour when in baseband or stereo modes. I would hear the audio on the radio the same time as I would on the VCR. Unfortunately there are no more SAP broadcasts here in the PDX area, no thanks to ATSC, and OPB decided to kick Golden Hours out of the studio in early 2008--they now exist, as far as I am aware, only as an audio stream.)[/b]

 

[nathannah]

It probably just depends on the processing chip in the converter box or cable box; there is that bit of conversion process that has to be done to either broadcast it or allow it to buffer on a hard drive in the case of a DVR, thus a delay (football/baseball viewers who prefer home radio calls over network blather and try to sync audio/video definitely would know this topic well). I know that I have two different cable box systems in my house and they delay, along with the difference between analog and clear QAM if you're not bothering with a box.

 

[fybush]

There's really no great mystery here. The important thing to know is that however you're getting your TV, even if it's over analog cable, what you're watching is a digital stream at some point along the way from the control room to you. Those digital streams have to be decoded, re-encoded and processed at numerous points along the way, and each of those steps adds at least a tiny bit of delay as signals are compressed and de-compressed and moved down the pipe through the transmitter plant or cable headend to you.

Normally, you don't notice the delay - after all, you have no way of knowing what "live" really is when you're watching TV at home. But as you observed while watching multiple TVs at once, those delays do add up in variable ways when you're watching different stations, or even the same station over a different transmission path.

This phenomenon explains why it's so devilishly difficult now for radio stations that broadcast, say, a football game to make it sync up with the same game being viewed on TV. The station might adjust its delay to match up perfectly with the cable box in the control room, but it could be entire seconds off from what the viewer watching OTA digital or over satellite might be seeing.

It's a whole new world, compared to the old days when everything was analog and "live" was really "live."

 

[oldiesfan6479]

Normally, you don't notice the delay - after all, you have no way of knowing what "live" really is when you're watching TV at home.

I have found that live feeds from a network viewed OTA through a DTV
converter on an non-HDTV seem to begin :06 late (per my atomic watch),
though I suppose this is probably the HD delay of the station itself. And
the same show/same TV via analog cable is delayed slightly more.

Case study: the 5:30 PM PT feed of NBC Nightly News aired on KPNX Mesa
coming up at 5:30:06.

Scott, since you can see the first Nightly show "live" at 6:30 ET, do you also
notice a :06 delay from real time on OTA?

 

[fybush]

I've never taken the trouble to look. I'll have to check tonight.

 

[landtuna]

I'd just be happy if the video and audio would sync up in the same broadcast. It seems that most network shows are always off by just a little bit to be noticeable. Never noticed this issue before the DTV conversion.

 

[fybush]

Scott, since you can see the first Nightly show "live" at 6:30 ET, do you also
notice a :06 delay from real time on OTA?

By my WWV-synched clock on the wall, "Nightly" came on my TV at 6:30:05 tonight. This via WHEC-DT Rochester, OTA.

(And this was a good night to try - they often step on the intro to Nightly when the local news runs long, but tonight we got to hear all of Brian's "On the broadcast tonight." Maybe they knew it's his birthday.)

 

[oldiesfan6479]

The NBC 'cast came up again--clean, from black--at 5:30:06* on
KPNX 12 Mesa (Phoenix market) OTA through the DTV converter.

There was no "Western Edition" banner after the open tonight,
so I don't know if it was the first left coast feed at 5:30 PT or
local playback of the east coast feed from 3:30 or 4:00.


*: Atomic watch on arm was in synch with atomic clock on wall. ;D

 

[Matt]

Digital delay creates some funny scenes, especially when the station is doing a telephone talk show with viewer call-ins.

One day, our host answered a call, only to be met with silence on the other end. He gruffly says, "Helloooooo" and the elderly lady on the phone said "...I want to wait until the other caller finished." The host explained to her that she had to turn down her TV sound and talk to him on the telephone. The irritated caller said, "That dumb lady you're talking to should turn it down. I'll wait until you get this dummy off the air. If she can't talk right, you shouldn't put her on. I've got something REAL to talk to you about." The show host thanked her politely, hung up on her and went on to the next caller...who had heard the whole thing and was in a laughing uproar when we put him on. At least, he wasn't getting confused by the delay.

Later . . . .

 

[anotherguyTN]

I have one TV with an HD tuner from Charter and the rest are on basic. There is a definite half second or so delay between the two and when we have the sets on the same channel in the living room and bedroom there is a definite echo when you're between them. Along with that the HD version of a channel has a delay of up to 5 seconds compared to the analog channel. That's really confusing when you hear the two.

 

[MCNDRWS]

I Have Identical Zenith Digital Receiver Boxes Connected To The Televisions In My Living Room And In My Bedroom. The One In The Bedroom Is Connected To A VCR. There Is A Distinct Delay In The Audio Between The Two Sets. I Have Also Noticed That When Talking With A Friend On The Telephone, My Over The Air Broadcast Of The Same Channel That She Is Watching On Digital Cable, Is A Few Seconds Ahead Of When She Receives It.

 

[kenrayc]

My HD dvr is a couple seconds behind the standard digital box in the other room, It annoying when someone in that room is watching the same NFL game, when a team scores a touch down pass they cheer before I actually see it.