Attn: TV Broadcast Engineers

[Tom WA3KLR]

In the switchover from NTSC to digital, one thing I notice now is that the TV sound and picture are rarely in sync.  I watch solely by receiving over-the-air terrestrial broadcasts.

Watching programs on my new HDTV, it is common to see that the sound is ahead of the action by as much as 1/2 second, although I think have seen the delay the other way also.  This is very annoying to me.

Is this the way of the future?  Are the individual stations at fault?

Perhaps future TVs should have a thumbwheel on the remote to adjust the delay, if this keeps up.

73........(73).

[KB2WIG]

It 'sounds' like there is some processing going on in the video end of things in the receiver....  If so, thats a crappy design  -  on the receiver end, I hope. Are the HD TV standards, standards?


My cable TV promised me that my tv will still work next spring..... 

klc

[Ralph W3GL]

Hi Tom...

Yes, I notice the same thing here on my old 19 inch analog set with the "Insignia" converter box.

Also the audio levels are NOT uniform through the 39 or so channels I receive down here. 

It appears the CBS station out of Philly (analog ch-3) is the one with the highest AF signal level...  I have to knock back the ABC and NBC channels by 3 to 6 db for listening comfort.

The rest of the channels (PBS, Bible thumpers, Spanish especially) are also not setting levels per some standard modulation level and are overdoing compression/expansion settings!  Program sound levels sometimes go from barely audible  to blasting within seconds.

Just my two cents worth...

[Bill, KD0HG]

TeeVee engineers have *never* been able to figure out audio and how to process same. Their average score in my book is from bad to wretched. They need to have at least *one* FM radio engineer around to show them how to do it right.

[W2XR]

Perhaps it has to be with the inherent latency present in the MPEG-2 video compression standard commonly utilized nowadays within the TV broadcast facility. The latency or delay present within MPEG-2 compression is typically on the order of about 250 msec. I believe the audio within the TV plant is uncompressed and therefore exhibits no latency, so the audio may actually precede the video by about 1/4 of a second.

The cure may be to digitally delay the audio by the same duration as the latency within the video channel. Everything would then appear in synch at that point.

Just some speculation on my part.

I have an inquiring mind (or is it an Enquiring mind), so I'd like to hear the truth on this one!

73,

Bruce

[ab3al]

as far as directv no problems here Sometimes the boxes come out with the default audio setting screwed up.. I have noticed the same with the ota converters....   if you are not using surrounnd sound go into the setup and turn off the dolby digital 5.1 and the optical output.  for those on dtv try using the hdmi cable.. instead of component. and make sure the audio settings in your tv match those in the receiver.  common problems with lazy installers.

yeah i sell the crap for a livin.

[ka3zlr]

Meaning Absolutely No Disrespect,

When the Kids are Out...it's off...an stays off... and when they leave..it's outta here for good after i strip out what parts i want to keep...it goes to the curb...

That Box and all the Gizmos that they can contrive folks into "Needing'...is No.1  on my Downsizing List...LOL.....of things to do....

I can't wait for retirement...I need to listen to a BallGame Hopefully it'll be on the radio,, I like to copy a Good Fist...I turn on the Drake....An when i want to copy a Channel master...I turn on one of the 390's..LOL...

Say No to Telemptyyerpocketvision...LOL... and say yes to a Good Network Analyzer.....LOL...

Give a man an analyzer....well some of you know the rest..

[KC4KFC]

I have an HDMI cable from the DISH Satellite box to the flat screen Samsung. Some channels have the delayed audio (doesn't matter if they are HD or not) and the audio RCA outputs of the very same box (analog) are not delayed. So if I have my hi-fi playing the audio, its' out of sync with the TV built in speakers. So obviously the out of sync lies in the box.

 I have also gone through two boxes which get very hot and pixelate often even with good dish alignment. The screens will freeze before the box dies. Sometimes you can re-boot the box to fix it. HD looks great, though. Old movies like Casablanca look incredible in HD!

I was also disappointed with the quality of installation. First dish was lag screwed through the shingles and then siliconed. When we had to replace the roof from the February tornado, the roofer (very good) said he wouldn't warranty the roof if they put that mounting back. I was able to get the installer to mount to an eave.

[Tom WA3KLR]

By the way, my TV here is a simple stand-alone Vizio 26" LCD, no system.

When I watch the 6:30 p.m. NBC network news on the local Philadelphia channel 10.1, the sound is in sync.  It is also in sync when I watch the local CBS channel 11 p.m. news on channel 3.1; they have the best video too.  So I suspect this situation is a matter of the station engineers.

I have been told in the past (not today) that the audio and video arrrive at the station by different paths.  There must be an adjustable audio delay at the station that is not being "riden" at most of the stations; all I can figger.

[flintstone mop]

It might be either a cable system or terrestrial, but no problems with synch from DirecTV. Sat HDTV and terrestrial are the better picture. Cable is compressing the HELL out of the picture to sqeeze more on the wire. Can't beat RF or fiber. I thought they fixed that a couple of years ago? I have been waiting for this moment for crystal clear TV since the middle 90's, when it was only CBS producing quasi-HDTV

Fred

[W1DAN]

Hi All:

This is a big problem with us broadcasters (I work in the industry) and you viewers. It is called "lip sync".

When we process digital video in a plant, the picture generally can take up to 250ms to process through an individual box (frame sync, production switcher, etc) in the TV station. Audio at worst is about 50ms. So far so bad.

There was not a standard for a time stamp in the combined (SDI) audio stream and video stream in the plant. There is one (called a PTS time stamp)  in the TV ATSC encoder (exciter) at the transmitter. So the ATSC encoder at the transmitter can accurately match the audio frames it gets at any time to the video frames before it gets transmitted and you receive and decode it at home. However if this encoder often receives poorly matched video and audio(due to satellite hops, poor editing, frame synching or running through a production switcher), hence you see lip sync errors that can be very bad.

Tektronix and other companies have created processes that match video to audio, but they have not been standardized. Someday a standard will be approved for in TV plant matching and things will get better. I along with you am waiting.

Some TV's have their own image display processing delay.

Also the BEST signal is from over the air ATSC. Sat and cable operators all reduce the bandwidth (and thus image quality). To me, cable is easiest to see the reduction in. Put up an antenna and switch between them to see the added pixelization and motion artifacts.

On the audio front, Dolby created a standard that the ATSC approved (called A53 or AC3). Dolby "assumed" that all the people who make TV content would "police" their level. This level is passed to the home not compressed or limited for a high dynamic range experience. In my opinion, advertizers like to have their audio about 10db hotter than average program level, so whe a commercial comes on, it knocks your socks off. Some stations do not know or are unwilling to match their average level to the reference "dialnorm" level that Dolby invented.

The answer...have broadcasters add compression and limiting in their air chain. This will create consistency, but you will lose the dynamic range.

Hope this helps,

73,
Dan
W1DAN
CBTE, CBNT
Boston

[AMroo]

Have installed and maintained digital TV systems.
There is a sync pulse in the system that’s prime purpose is to provide lipsync
It can take up to 40 secs for the thing to sync up when you first change channel, but it should drift back in ok in less time than that.
Also during this time the teletext may not be at "eye height" but will also come back in. It can some times be seen in the middle of the picture when first changing channel.
Also another problem is that they often don’t use translators. Instead the system uses on channel (same frequ or in band) remote transmitters to provide distant coverage. The main and remote are phased locked to a signal derived from a local GPS Rx at each site. Its synced by the deriving a 10mhz signal from the GPS system as a ref. Adjustments are done to sync pulses so that the propagation time from TX to Rx is taken into account.
Between a remote in band (on freq)transmitter and the main transmitter there is a theoretical  thin line where the two sync pulses over lap or can be too far delayed. Problems can be experienced in these areas .
All attempts are made to put these sync problem areas into places were not many people live or that are not considered important to coverage. So maybe you need to shift!!! Velcome to ze dijtal vorld mine heir friend.

[Tom WA3KLR]

Dan and 'roo,

Thanks for the information.  The delays I have seen lately stay there.  I have seen small delays at times, get walked in to sync.

So I guess we just have to bear with the new Always The Same Color system and wait for the lipsync thing to get squared away.

(Hey I just hit 1000 posts!)