Lip Sync Problems with New Digital Displays?

An anonymous reader writes "With all of the new digital TV displays flying out the door, its easy to to think that life is good on the road to high definition. But, as Audioholics reports today, cheaper displays are using inexpensive processors that result in video delays of up to 60 milliseconds (that's about 2 frames of video). This means that the video processing (deinterlacing, video scaling, etc) delays the picture so that the audio is out of sync. Add to this inherent delays in some LCD and plasma units and the problem can be more than a little noticeable. As of right now only a few manufacturers are building audio lip-sync delay into their products to compensate."

Comments

Re:why do companies do this?

[grub]

Back ~1990 I bought a device from Barkus Berry Electronics which delayed higher frequencies a few ms to let the "slower" bass and low-mid frequencies play catch-up. The idea was that the woofer and midrange had a longer stroke than the tweeter which was required to make the sound. This let the bass and mid leave the speaker at the same time as the high end stuff.

I still have that unit, it really seems to "open up" the music more.

Re:why do companies do this?

[... James ...]

The Onkyo TX-DS989 I bought in umm... 99 has an audio delay feature. Digital displays (and digital content) were hardly as common then as they are now. Doesn't sound to me like they were working around this problem.

HDTV formats

[Genjurosan]

So what happens when the input format changes? i.e. Will the equipment freak out when 1080p is sent to it, and then the unit is forced to convert to 720p? Basically, I hope they compensate for the variety of signals out there if they can't fix the problem at the source.

Analog Signal Buffering

[Anonymous Coward]

Is it even possible to do analog signal buffering, or will the signal be converted to digital to buffer it for a few milliseconds and then back to analog?

I suppose it is possible to do analog signal buffering now that I think about it. Some guitar AMPs have a delay feture, which I'm sure is all analog.

Sucks for PCs, and on input too

[dbrower]

None of the packages I've seen for capture have anything to calibrate and shift the input chain for variable delay between sound and video encoding. It's a problem things like MythTV might profitably spend some time thinking about. Think about why there are clapboards when shooting film.

-dB

I ran into that...

[JediTrainer]

...or at least my future father-in-law did. My fiancee's parents recently bought a very nice Samsung HDTV system which had this problem. The audio was way out of synch with the video, and it was quite noticeable at times.

Samsung ended up sending someone to the house, and replacing a board in the TV with a newer model, and that seemed to fix the problem.

I don't understand why they couldn't have anticipated this problem before they shipped the TVs, though. Isn't that what QA is for?

Re:why do companies do this?

[haystor]

We frequently watch hockey with the radio on going. The video comes in a second or so behind. This makes the radio play by play seem psychic at times.

"He shoots he scores!"
Then we see the shot and the goal.

Sure it's the display device?

[... James ...]

I frequently see audio delays on HDTV feeds being displayed on my DLP projector. Change the channel (to another station broadcasting at the same resolution), and the problem goes away.

It's either my crappy Scientific Atlanta HDTV receiver or the feed itself.

I really have doubts about this article.

Re:This will hurt video games

[Jotaigna]

first you introduce audio delay with buffering technology and then you intruduce user input delay using psychotropic technology.

Seriously, the post makes reference to the use of cheap proccessors hence the video delay. By 2006 the expensive processors of today will be cheaper, and eventually cheap enough.

Real Problem...

[braddock]

I was working on a video conference system a few years ago, where latency is everything. We got a huge $15k plasma display (at the time), only to discover it had something like 90 ms of latency! Since we were already pushing our latency budget by sending signals across the country and loosing frames here and there through video processing equipment and codecs, that 90 ms was more than enough to push us over the edge and make the system very difficult to use for natural conversation, and throw the audio/vidio sync visibly out of whack. The plasma had to be replaced. Three frames may not seem like a lot, but it is quite noticable.

I've delt with a lot of high-priced high-quality plasma systems over the years, and the lesson is definitely "Buyer Beware". The high quality 56" plasma systems can be stunning, but remember that you're also investing thousands in a device with a fairly limited lifetime, and no real industry-wide quality standards and more marketing buzzwords and cheap tricks than you can shake a stick at.

If you using plasmas as a computer display you will see even more artifacts. I've seen widescreen plasmas that could not accept any resolution modes of a correct aspect ratio. Many displays use a great deal of image processing to apply tricks to make the display look good, but sometimes the processing can seriously disturb things like computer text. I've seen apparent color segmentation problems on a lot of displays, and just a lot of artifacts in general.

-braddock

"cheap processor" is a myth.

[Bender_]

Both original article and slashdot posting are quite inaccurate..

The delay is not caused by cheap processors, that is a myth. Just think about it, even delaying the video by 1 second will not reduce the required processing power...

In fact the delay is a technical neccessity for some of the algorithms employed in modern television. For example motion interpolation for 100Hz TV requires the knowledge of at least one frame in advance.

Also the "delay" in TFTs, as mentioned, has nothing in common with the delay due to video preprocessing....

The only remedy for this problem is to have an option to turn all the preprocessing off for video games and have an artificial audio delay, so it matches the video. Nothing that is out of bounds for an average TV...

Re:"cheap processor" is a myth.

[ivan256]

The delay is not caused by cheap processors, that is a myth. Just think about it, even delaying the video by 1 second will not reduce the required processing power...

We're talking latency here, not throughput. They're two seperate things.

Let's say you have a pipeline of frames you're processing. There may be multiple frames in flight at different stages of processing. The longer it takes for for a frame to enter in one state and leave in it's final state doesn't nescicarily have any impact on the number of frames you can process per unit time if you increase the number of frames in flight. A processor with fewer steps of the same length along the processing path, or a processor that can complete each step more quickly will reduce the latency. Such pipelining is a common technique for increasing the latency of an operation in exchange for throughput.

Re:"cheap processor" is a myth.

[Bender_]

As I wrote - framebuffers are expensive, you do not want to increase the number over the bare minimum.

P.s.: We are talking about signal processing in a cost efficient architecture here, this is different from render-to-texture algorithms in overpowered 3D accelerators.

Adding a fixed delay will not resolve the problem

[cyclocommuter]

If you have a Samsung DLP and you are experiencing this problem, adding a fixed amount of delay does NOT guarantee a fix. The reason is that in Samsung DLP sets, the delay is intermittent. Often times it's barely noticeable (60 ms or less), but sometimes it spikes to as much as half a second. I used to have the Samsung HLN567W but I returned it before my 30 days guarantee was up. Picture Quality was great but the intermittent audio/video sync issue was driving me nuts. I first read about this problem (on Samsung DLPs) last August, I bought my TV last January, and apparently the problem still exists in new sets being sold currently. That makes this problem at least 9 months old... looks like the resolution is not easy otherwise Samsung could have fixed this a long time ago. With all the high tech circuitry being added to consumer electronics nowadays, regular consumers are now becoming beta testers for these consumer products too. Welcome aboard!

Re:Sucks for PCs, and on input too

[takev]

It is actually much worse. The clapboard only syncs the film/video to audio at a single point, but as time processes during a take the audio and video will slowly get out of sync.

Thus today's syncing technology consists of:

• blackburst (which makes sure the video/film camera ticks at a consistent rate)
• word clock (which does the same for digital audio equipment)
• SMPTE/EBU LTC time-code (uses an audio channel to set the frame number)

The SMPTE LTC code is both recorded on an audio stripe (channel) of a multitrack audio recorder, and on an audio stripe of the film-camera. It is also possible to sync MIDI and DV-timecode to SMPTE time-code.

Now, there is equipment that creates all these signals, or you can build a chain of syncs. Blackburst is often the master, on which the word clock and SMPTE time-code is synced with a PPL (phase locked loop).

I just started in the video and film business and I was stunned by all of this.

Stupid Oriental Movie Jokes Notwithstanding

[Moryath]

There is a more sinister side to this - monitors that can't keep up, get into BIG problems when dealing with another venue that is pushing towards them more and more: VIDEO GAMES.

I'm actually serious. While the normal populace may scoff and deride those who play games like Soul Calibur or Street Fighter until they can actually count how many frames a particular move takes to execute - and how many frames from when the button is pushed to when the move reaches its damage point - everyone likes nice, crisp controls.

They want to know that when they push that button, it went into the system immediately.

Now you're talking about adding a possible 4-5 frame delay to the entire system - but you CAN'T make the video game system have the same delay, it'd have to recalculate everything backwards in time to compensate.

So what do you do there, huh? It's a pretty crappy workaround solution.

Overclock it... err faster processor! DVDO/doubler

[telemonster]

If AMD can sell 2ghz chips for $100....

I use a program called dscaler (sourceforge) to upscale my laserdisk player for CRT projection, so far it hasn't been that noticable, and I'm using an 800mhz Athlon.

I find it hard to believe that it would be that difficult to incorporate a faster/better engineered processor or DSP to handle the video scaling functions, especially in plasma displays that start at $3000 and higher.

Does the DVDo units (the outboard device that pretty much killed the line-doubler market) suffer this delay? That unit was at the forefront of cheap line doubling, if it can upconvert without causing too much of a delay in audio there is _NO EXCUSE_ why the embedded chipsets in modern sets aren't able to cope.

Re:Not specifically a plasma display problem.

[Rasvar]

An even better answer, of course, is to scrap this digital TV crap. The best digital TV signal doesn't hold a candle to the best analog TV signal. All that digital buys is the ability to squeeze another 150 shopping channels onto every satellite at the expense of video quality - but that doesn't matter, its marginally better than VHS, so what will the consumers ever know?

Have you ever watched a "properly installed and configured DTV running in full HD"? You obviously have not. If you have seen it on a crap setup, it won't look any better. So far, 90% of the HD systems I have seen have been incorrectly installed. Almost none of the stores have their systems set up properly. Best Buy usually has only one or two floor systems set up almost correctly. If it has a coax, it is not going to look any better then Analog. OTA Digital TV broadcasts are far superior to the analog broadcasts. I have a Samsung 31" HDTV [CRT, I don't trust plasma or LCD and don't have room for a projector]. Have a Samsung DirecTV HD receiver. The SD broadcasts look like crap when compared to the the 1080i HD broadcasts. Digital 480P is slightly better than Analog. Fox is still only broadcaster their widescreen at that. CBS and HDNET seem to do the best job on HD broadcasts.

However, I would say that most of the HD systems installed today are not used correctly becuase they are either set up wrong or the installer never clearly explained how things work. Usually a combination. I spent three hours over Christmas showing a family friend how to use his 72" HDTV in true HD mode. He was amazed. He thought he had been ripped off becuase everything was streched and fuzzy. Installer never explained to himthe proper input and settings to use to get the HD broadcasts. He was mezmerised when I finally showed him HBO HD. Technology does not good at all if no one knows how to use it or install it correctly.