DTV sound synch

Even on , supposed, live feeds , often lack of sync in the UK You mention classical music. I cannot listen to proper music on any of the UK freeview channels because of some sort of overload distortion. This is same on 2 makes of set-top box , is it just Rowridge, IoW, transmissions/ local multipath problem to me or do others find this issue in the UK? Is there a name for this distortion ? full orchestra with the brakes on is fine but go forte and clipping sort of compression distortion - if only they still had test-cards with pilot tone these days, so I could scope. And also related, no time signals these days, no seconds of time mentioned anywhere on digital.

There are some articles on

Sound on Vision

iPlayer rules OK?

I'm in the UK, but different receivers introduce their own differing delay. As you'd notice with two on at the same time. And this is just DTV tuners - not complete sets which may introduce a sound delay to compensate for that in the display technology.

What I'm not sure is if the picture is still in sync with the sound on these units.

There have been reports here of a re-boot sorting gross sound sync problems on some makes.

Must be a local to you thing. I only ever listen to TV sound through a decent external sound system, and although there are sometimes problems, it's not fundamental to the system. Indeed I use FreeView tuners for radio these days.

One thing you could check is your not overloading the input to whatever you're listening on - some STBs can supply much more output than analogue ones, if things are peaked to 0dBFS.

I use one most of the time and another to record another digital ch concurrently off-air or for a second recorder on a few occassions. The second one just feeds an earpiece so I can check the sound of that one without any picture hook-up is the same as the main one with on-screen ident, in case of r/c miskeyings. They never agree but they must each be in sync within themselves , but not checked with 2 TVs simultaneously.

On the music distortion , there is a an UHF aerial amp in line, suppling both set-top boxes. Sometime I will try a different one to see if it makes a difference. Without an amp some channels become "no signal" although ok for BBC4 , must try set-top box digital radio 3 sometime.

I don't think anything you could do to the incoming RF data stream could cause the problems you report. I'm in a very strong signal area as regards UHF - I can see the Crystal Palace mast which is about 5 miles away. The aerial fed direct to an analogue TV caused overload - but no such problems when fed to a DTV box on trials. But of course I've not tried them all.

Its consistently the same , 2 different converters, 2 different aerials and downleads. So unlikely multipath problems which ttend th change with weather and time of day etc. I think there is audio overload on general sound eg when there is an argument, elevated voices and speaking at the same time - its just its more obvious with an orchestra.

When I dig it out I will try another uhf amp, then it will be a full-on mystery, if still the same audio problem. Never any picture problems other than nearby motor use or very bad vehicle ignition

Ya know, once upon a time, "Broadcast quality" used to mean something.

Now it appears to mean, "How much advertising revenue can we cram into something?"

Nobody gives a s*it about "doing it right" all the way down the line from the CEO to the techs.

Jeff

Yeah, a good plot to get rid of over the air TV all together. Just think about all those extra cell phones they can add to the system and make big money! ALong with all those other services that can be added for a fee!

Jamie

I think to some extent, that depends on the 'quality' of the broadcaster involved. I watch a lot of HD transmissions on sat, and most are superb. I've never seen a sound / vision sync problem that I can remember. However, I also watch some of the cheapo channels, and the whole production quality can, as you say, be very variable. On these channels, I have often seen the sync problem, so I guess that somewhere along the line, it's caused by cheap production techniques, or maybe something to do with the bandwidth (cost) of the data link from the programme producer to the uplink station, or maybe the quality (cost) of the transponder that they are renting on the sat ?

Arfa

I'm surprised there aren't more complaints about this. Two HD television sets connected to the same antenna system can have an audio difference between the two. Weak signal conditions seem to be the worst, with very obvious delay just before the picture breaks up.

There are probably several reasons for the discrepancy, but there is no excuse. Audio-video sync shouldn't be a problem with a digital system, but the current HD system is obviously weak in this area. Perhaps there is a delay due to the need for error correction when signals are poor. If so, why isn't one delayed so both audio and video are presented at the same time? It might take some extra memory to hold delayed data, and maybe an algorithm to shed an occasional video frame. Or is it the other way around, with audio leading the video?

I haven't seen this mentioned in Consumer Reports television reviews, so few of us are complaining about it!

Fred

On 1/29/2011 11:03 AM Fred McKenzie spake thus:

Judging by the behavior of my system (set-top DTV box, Zenith DTT901), I'd say that the audio is simply sacrificed for the sake of displaying video. When there's a marginal signal coming in, the video will continue to be displayed, albeit with some break-up and possible freezing, while the audio simply drops out.

On Jan 29, 3:36=A0am, Jeffrey Angus wrote: > Ya know, once upon a time, "Broadcast quality" used to mean > something. >

It still does mean something and if you ever thought revenue WASN'T a part of it, you're just wrong. I get to see 'broadcast quality' video from the 60's and 70's at work and while it was good in its day, it doesn't hold a candle to what you have now. I'm one of those 'techs' and I can tell you we DO give a hoot about how it looks and sounds.

G=B2

Back in the days when there were engineers , they designed a colour TV system In slightly degraded signal conditions you lost colour - could still follow a film say Worse propogation and picture became snowy - still followable Worse and sound became noisey and syncs being lost - just about followable Finally the sound would go

These days its all arse about face, sound is the first to go and colour is the last to go

Newest Sci-Atlanta DTVHD-DVR, TWC here. Don't notice a lot of sync problems. Being a musician I would notice even a few milliseconds.

More problems with picture fizzle-out accompanied by audio drops and buzz on HD channels. Signal tested recently. Found to be high-normal in the HD range. Nothing to bitch about except when Discovery-HD fizzed and buzzed every 10 seconds. A new DVR fixed that.

It's very unlikely you are seeing broadcast electronic video from the 60s and 70s as good as it was then. It'll have been transferred a few times as tape formats go out of use - and the transfer equipment likely towards the end of its life. Plus the fact that even a single generation of quad VTR caused noticeable degradation, and most of the stuff which has been kept will be two or more generations.

On 1/29/2011 12:51 PM Meat Plow spake thus:

OK, but how about other channels? The out-of-synch problem seems to be the worst on a local public station that runs a mish-mosh of programming with *extremely* low standards for any kind of production values, but I've noticed it even on network stations (NBC, ABC, etc.) where even speech doesn't match the speaker's lips.

Oddly enough, I've never experienced *any* of those problems with DTV. Just audio drop-out, but no buzz, hum, distortion, etc.

It IS unlikely but I work in Hollywood and am one of the few who still get (got?) to work on quads so it happens to be true. I was watching the original 2" quad tape played back on an Ampex AVR-1 just a few weeks ago. It was an NBC Danny Thomas special (low band color so there was some moire) from 1965 with Johnny Carson, Bill Cosby, Tim Conway and others You're also mistaken about how many generations you can go down before you have noticeable problems. Network on air tapes were a minimum of 3 generations down. Mind you, it's necessary to adjust things properly unlike the newest digital machines that are close to idiot proof but will tie you in knots with the myriad settings.

You probably never saw a Super High Band Pilot quad tape where the time base reference was recorded analog along with the analog FM video. Zero velocity errors as the pilot was the sample clock and any timing errors on the video were also in the pilot so the error was nada. That came out in the '70s along with the first 1 inch decks which had the 'trick' video of slo-mo and still frames which were previously unavailable to local stations. Quad died fast after that but not until having a 20+ year run.

I was just repairing Ampex AVR-3s this afternoon. G=B2

I started work for the BBC at their main production centre in the early '60s in the days when some drama and LE was still live. And therefore saw the introduction of colour in the UK from the sharp end.

And you never noticed the degradation compared to live progs? With only even one generation?

C-format degraded things too.

DigiBeta was the first tape based system I saw which in general didn't degrade things noticeably.