DTV question..

[KC]

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

 

[Deke]

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

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

D

 

[KC]

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

D

The same problem exists OTA or cable. Input is via the rf connector.

KC

 

[KC]

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...)

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

KC

 

[KC]

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...)

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