A lot of channels seems like their is a minor sound delay, just wondering if this is a freeview problem or humax problem.

Interesting. I thought I'd noticed this too. Not being experienced with FreeView I assumed either:
[list][*]I was imagining it, or[*]it was a general freeview issue, or[*]it was because my video and audio paths are different (Video->scart to TV, Audio->to surround amp)[/list]
I only seem to notice it on very close up shots of face and lips, where the speech is clearly visible as well as audible.

I think I can see a slight delay in the audio too. It's small, but quite irritating once you notice it.

I've tried two audio paths which both gave the same results: optical digital -> surround amp, and RCA plugs -> surround amp.

I also watch DVDs via a SCART signal which is passed through the Humax, with coaxial digital output to the surround amp, but this source does not suffer from a sound delay.

Looks like this is a problem with the Humax or Freeview itself.

I can see lip sync issues being reported by setpal boxes, PaceTwin, Sagem6240, Netgem i player, Humax F2-Fox T
Sagem PVR 7280T, Panasonic TUCT20.
Sky+ forums at first suggested it was just a SKY+ issue but alas it affects a wide range of devices. The Tivo community web site also discuses the problem.

I'm going to paraphrase an AV website, to avoid copyright issues, as it gives a samll insite to the problem.
It’s one of the most annoying and widespread problems in and it’s probably been experienced at least once by most people reading this; it’s caused by a depressingly wide range of different problems; there’s no knowing when it’s going to appear; but when it does it can completely ruin your enjoyment of a film or TV. What are we talking about? Lip-synch error - when the movement of actors’ mouths in the picture doesn’t tally with the words they’re saying on the soundtrack. Sometimes the problem can be so bad that even a Hollywood blockbuster can look like some poorly dubbed foreign language film.

Causes of lip synch errors include: failure by (especially digital) broadcasters to synch the audio and picture tracks correctly at source; digital TV receivers ‘glitching’ while decoding their pictures so that they’re decoded slightly slower than the sound; and big differences in the length of audio and video cables in a system (a common situation for people using projectors). Ultra common is also the picture processing employed by today’s digital displays - be they plasma, LCD or DLP in nature.

On other DS threads I remember reading about channel 4 and E4/E4+1 being persistantly bad for a time on freeview, but it looks like the broadcasters may have done something about it as it now can be found on other channels.

Yes I have also found some occasions when the sound and video tracks are out of synch (hesitate to call it 'lip-synching' since I always understood that to be the delicate art whereby an actor actually records words onto a sound track to synchronise with what he can see on screen after the film has been shot - either for foreign-language edition purposes or to overcome sound issues during the original shoot )

As far as I can tell it's only happened when viewing progs I've recorded - never noticed it on live transmissions. My solution is to stop the recording and immediately start again - this seems to have fixed it up until now.

Barry

Nope that is EXACTLY the term used "in the trade" for the delicate art of persuading an MPEG decoder to play the video and audio out at exactly the same moment according to the presentation time stamps (PTS packets) in the MPEG stream. It's just faintly possible that the errors seen are at the broadcasters end if almost every box on the planet is showing the same lip-sync errors

(can't say I've noticed it myself and I'm usually very sensitive to it (apparently some human brains can cope quite well!))

Cliff

Sorry mate, but that's what comes of being in different 'trades'!

Having in my past been involved in producing sales training videos etc for Henry we couldn't afford to re-shoot them for all the different Euro-tongues, so they were subsequently dubbed into Finnish or whatever by actors who were expert 'lip-synchers'. Having appeared myself in one such video I can tell you BTW that it's very disconcerting, when it's well done, to watch yourself on screen speaking with someone else's voice. It's as if you've done a Faust and sold your soul to another.

OK, I know, way OT!

Barry

Barry,

Ah but I'm in the "STB/PVR trade" so my use of "lip-sync" MUST be right!

Cliff

I agree - you are the home team!

Baz

I am very sensitive to lip synch problems. The F2-FOX T used to be very prone to this until the OTA update earlier this year, since when it's been considerably improved. I found that if the channel I was watching went out of synch, then changing to another channel and back again usually corrected it. In severe cases, a reset to factory defaults seems to cure the issue for many months.

Geoff

Geoff I am starting to read a lot more things saying this elsewhere on the net about a variety of freeview and sat boxes (i.e. changing channel and then back again to correct it) Wondered if people see the lip out of sync issue again could try doing this as well which may help. Not sure what you can do if its an unattended recording though!

Marc,

My guess is that if the remedy of switching out of and back into a channel works with a live broadcast, then any perceived sync concerns arise from some lag in the decoding within the box of the audio compared with the video streams at the time of decoding ie the fault isn't with the broadcaster. In which case your digital record will also be OK ex source, so unattended recordings are not an issue.

This is also confirmed by my own experience (see post above) of sync irregularities when watching a recording. Stopping and restarting the recording does the trick.

Barry

Mine is a special case not included above. I have my headphones connected to the humax. Sometimes I find that I am listening to the Humax while watching the channel in analog on the TV. Then the audio delay is really uncomfortable and I quickly switch the TV to the Humax.
Edit. I meant this to be a seperate post. Sorry Barry.

No apologies needed!

Yes I can imagine that would be disconcerting. I've noticed there is at least a second difference between the analogue and the digital signal, but I can't think why. (Enter Cliff?) I can understand a time lag between a terrestrial and a satellite signal (long way for the data to go and come back and all that), but Freeview is also terrestrial. Maybe it takes a receiver longer to 'translate' digital data into sthg viewable than it does digital data?

Like yourself I often use the audio output to enhance the sound, but only to my audio hi-fi. Still can't understand half of what New Yorkers are saying in US films. Another age issue I guess!

Barry

I think the main source of the delay is the fact that the digital signal is created by the broadcaster encoding the analog video source to MPEG2 on the fly. This process is not instantaeous, hence the delay.

I do not no if this is still the case, but if you unplug the aerial on a freeview box, the sound and vision will keep working as if nothings happened for 2 seconds then it will go blank and no signal. So we are all watching live tv 2 seconds behind live.

Some boxes suffer more than others, for example, the PACE DTVA was good until it received the first TOP UP TV software upgrade to allow it to read a smartcard, this software update caused lots of problems, particularly with ITV, channel4 and top up tv channels! This was soon rectified with another software update and all lip sync issues went away.

Other boxes seem to trip up when there is a glitch or interference, causing the picture to lag the sound or vice versa, if there is no system in place to correct this problem then the only fix is to change channel and back again.

Yup, that's exactly why digital telly lags analogue by a second or more - it's MPEG encoding on the fly and MPEG is a non-symmetric encode/decode process - it takes FAR more horsepower to encode than decode and to be able to do it with only a second lag shows that the broadcasters must have some majorly powerful kit that does the encoding (in silicon rather than software obviously!)

Another effect you may find is if you watch the digital video out of a PVR on a telly but route the audio out of the diital-optical-out and theough your own A/V decoder to your speakers/headphones.

Unless the A/V decodes audio at exactly the same rate as the decoder inside the PVR decodes the video then you can get a minor sync'ing problems there too.

Cliff

Originally, this was my #1 suspect for this oddity.

But the more I thought about it, the less it made sense:

- my video and audio leads (and paths) do differ, but that difference is constant.

- surely, therefore, any audio lead/lag caused by my surround Amp processing at different speed to the Hummy would be fairly constant.

This is not what I see at all though. 90% of the time, there is no visible lip synch lead/lag. When I do get lead/lag it varies from just barely noticeable, to being in the "badly-dubbed KungFu film" category. Such a big variation in the amount of lag wouldn't seem to be logical if it were introduced by path/lead length differences - it should be mostly constant. This smacks to me of some variable "processing overload" introduced error in the audio/video streams either at the broadcaster end or in the Hummy, or some form of signal corruption (possibly even in whatever time-sync marks the MPEG-2 stream uses)

-- Rob

Rob,

I'm not sure but maybe the audio is VBR so at times of increaed complexity a decoder might take more time over decoding it and slip further out of sync?

Cliff

E4+1 Sounds seems to be always out of synch, has anyone else experienced this.

Hence the '+1'?

Barry

It seems to be sometimes up to a second out and sky news as well.

I have noticed this on some analogue broadcasts. I would not mind if the sound arrived a few milliseconds before the video portion because I could put it through my mixer and stereo digital delay (set to mute the direct sound and only return the effected signal).

Unfortunately, it's usually the other way round and I am helpless to do anything about it... aaargh!

Hmm - just about every other issue I have read about here is survivable. But A/V out of sync by up to a second - that's a biggy.

Is this an occassional or a typical problem?