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DTV question..

Just upgraded from an old analog tv to a Samsung DTV. The first problem I noticed is the lip sync audio-to-video time delay on NBC's national digital programs. While analog broadcast has some small time delay, digital has 2x-3x more delay, making it almost impossible to watch. Local station in-house digital programming does not have any more delay than analog, but as soon as they switch to national programming, the delay goes to hell. ABC & CBS does not have nearly the delay that NBC has. I brought the problem to the attention of the local NBC station, but they said & did nothing. Does anyone else notice the problem, or is it generated by my local station?

KC

Reply to
KC
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I might suspect some of each...

I work for a NBC local station, hopefully not yours(grin). We had some issues locally that kicked in when we installed a character generator to do severe weather. It put some delay in the video but the audio went via a different route - ended up being sent before the video. That doesn't happen in nature and is VERY noticeable! We ended up buying a audio delay and dialing in 150ms in the other path. Since local material bypassed the HD character generator, local stuff was fine.

I'm not entirely convinced there isn't a problem in New York too though. I've seen the lip sync *change* dramatically during a program.

We're in the process of replacing our main control board for HD, which should keep all the audio and video in the same path & get this side gear like character generators out of the way. I might expect your local NBC station (again, hopefully that's not us!) will be taking similar steps. A lot of stations have had to cut corners to get HD on the air at all and it's going to take awhile to put together the budget to do HD the way it should be done. (that new transmitter & antenna weren't cheap, and a lot of stations have to buy it all twice! - luckily we only had to buy once...)

Reply to
Doug Smith W9WI

You didnt mention what your A/V setup is, but what source are you using for your video/audio?

D
Reply to
Deke

g

=A0A

Thanks Doug. A very informative reply. Sounds very similar to what I'm seeing. I forwarded it to the local station engineer.

KC

Reply to
KC

Analogue should have no noticeable delay in its basic form. If it has it's down to some extra processing, usually in the video. And the broadcaster

*should* compensate for this.

However, most modern TVs add in some video processing or have an inherent video delay by their nature. Better ones delay the audio to retain sync. Can be a problem where a CRT set used mainly as a monitor with an AV system is replaced with a newer type - as I discovered with my DLP setup. Ie the sound came direct from the AV setup which also switched the picture source.

However, you appear to have a problem with only one channel which rules out this. I'd suggest you ask neighbours if they have the same problem as it could be a funny with the tuner in your set. The reason I say this is I have several DTV tuners here and they all produce slightly different delays to the sound (ignoring that produced by the TV itself) so it is just possible for this sort of fault on just the one channel - or rather group of channels.

--
*24 hours in a day ... 24 beers in a case ... coincidence? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Reply to
Dave Plowman (News)

g

=A0A

I began a dialog with the local NBC station engineer. Here's his opinion of the problem:

"Part of the problem (foundational) is that SMPTE (creates standards for television) chose not to include a method to synchronize video and audio packets in the new digital standards in order to leave more bandwidth available to improve quality. As a result, there is no way to exactly re-match video/audio once they are separated from one another. Networks and stations throughout the country struggle with this problem and vendors are working hard to develop equipment to help meet and "hopefully" correct this issue. My (his) personal position is that SMPTE failed to ensure a standard that enables video and audio to remain synchronous throughout the encoding and decoding process. This failure to create a solid standard now requires each network and station to have to go out and purchase additional equipment to correct for a flawed standard. We are building on a cracked foundation."

All that being said, I see a huge national backlash against digital TV come Feb. '09. A large portion of folks will buy new DTV's, only to find out they have a nice picture they can't stand to watch because of lip sync problems. I see congress & the FCC being swamped with complaints. The whole mess is easily comparable to government "aid" from the FEMA!!!

KC

Reply to
KC

I'm not in the US but I'll bet that's bollocks. Such constraints will be to pack the maximum number of channels into a given bandwidth thinking the punters won't notice or care.

--
*"I am " is reportedly the shortest sentence in the English language. * 

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Reply to
Dave Plowman (News)

Exactly. Those despicable and disingenuous DTV transition PSAs (or are they paid spots?) drive me nuts and ought to be challenged since they represent government propaganda, declaring that 'digital is better' and 'better picture' and all sorts of other unctuous claims, instead of making a factual declaration that the spectrum space is being reclaimed for Homeland Security and private auctions and alerting the populace dependent on OTA reception to the deadline without the dog and pony show.

Michael

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msg

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