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Lip Sync Problems with New Digital Displays? 311

Posted by simoniker from the kung-fu-movie-syndrome dept.
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."
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Lip Sync Problems with New Digital Displays? More

Lip Sync Problems with New Digital Displays?

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  • Ah, that explains it. (Score:5, Funny)

    by grub ( 11606 ) <slashdot@grub.net> on Friday April 23, 2004 @01:28PM (#8952532) Homepage Journal

    I was wondering why Ron Jeremy's tongue was trailing behind the licking sound.

  • Aaah... (Score:4, Funny)

    by Doomrat ( 615771 ) on Friday April 23, 2004 @01:30PM (#8952557) Homepage
    Really? Damn. I was beginning to wonder why everything on T.V. was a badly dubbed German show.

  • All right! (Score:5, Funny)

    by SCSi ( 17797 ) <corvus@v3.1415926adept.com minus pi> on Friday April 23, 2004 @01:30PM (#8952561) Homepage
    Now the lips in my old gozilla movies will be in sync! Deaf people everywhere are rejoycing!

    • Re:All right! (Score:5, Funny)

      by Anonymous Coward on Friday April 23, 2004 @01:36PM (#8952632)
      Yeah, those movies featuring rogue spyware programs smashing Tokyo buildings are pretty cool.

    • Stupid Oriental Movie Jokes Notwithstanding (Score:5, Interesting)

      by Moryath ( 553296 ) on Friday April 23, 2004 @02:43PM (#8953305)
      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.
      • There's a solution, though. Make all games work according to the infamous FinalFantasy fight-in-turns system!

        Can you imagine how GranTurismo would be in a move-in-turns scheme?

  • ah (Score:3, Funny)

    by pizza_milkshake ( 580452 ) on Friday April 23, 2004 @01:30PM (#8952562)
    so *that* explains the lip sync problems in those old kung fu flicks.
    • Any one seen the kung-fu spoof "kung pow".

      For anyone who likes cheezy kung-fu movies, will emencly enjoy it.

      The best scene, is when one guy asks other guy, what's happening ?

      And then you see the other guy, talking for about 10 secs, and finally hear the dubbing "I dunno".

      I almost fell out of my chair ,

  • why do companies do this? (Score:4, Insightful)

    by trmj ( 579410 ) on Friday April 23, 2004 @01:31PM (#8952565) Journal
    "As of right now only a few manufacturers are building audio lip-sync delay into their products to compensate."

    So once again, another company is working around the problem instead of fixing it. This seems to be a bad trend in technology these days.

    • Re:why do companies do this? (Score:4, Informative)

      by cexshun ( 770970 ) on Friday April 23, 2004 @01:34PM (#8952595) Homepage
      Actually, that's the only way to fix this is a work around. As not only the article states, but common sense states that to fix this, you have to make video processing faster. We cannot do this with our current technology. So we have to use a work around until the technology catches up.

    • 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? (Score:4, Funny)

        by lildogie ( 54998 ) on Friday April 23, 2004 @01:44PM (#8952716)
        It also explains why drummers keep creeping up the tempo.
      • 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.

        To me, that sounds like phase-shift correction, in a way. More accurately, phase-delay correction.

        Any time you low-pass a signal, there is going to be some sort of phase delay as a result -- whether that phase delay is a result of an active/passive crossover, or the physical attributes of the speaker, the problem is the same.

        Phase correction

    • Re:why do companies do this? (Score:5, Insightful)

      by brokenwndw ( 471112 ) on Friday April 23, 2004 @01:35PM (#8952617)
      How exactly is this a work-around? Will you really notice if the entire feed is delayed by a fraction of a second? It seems to me like the right thing to do-- impose an external constraint that the audio and video feeds should be synchronized rather than count on the processors to be fast enough to make the difference unnoticeable. It should help in the future if people want more sophisticated transformations to be applied to either component of the stream.

      • Try playing Nintendo on such a TV (Score:5, Insightful)

        by tepples ( 727027 ) * <tepplesNO@SPAMgmail.com> on Friday April 23, 2004 @01:38PM (#8952659) Homepage Journal

        Will you really notice if the entire feed is delayed by a fraction of a second?

        If the feed is coming from a video game console that's responding to live user input, I'll certainly notice llaagg. A delay of 60ms can spell the difference between a hit and a miss, adversely affecting game scores.

      • Re:why do companies do this? (Score:5, Insightful)

        by Tiroth ( 95112 ) on Friday April 23, 2004 @01:42PM (#8952695) Homepage
        What if the audio is coming through your stereo, not the TV? The the delay does nothing for you.
        • What if the audio is coming through your stereo, not the TV?

          Then your stereo probably already has this feature. You just have to setup the delay per channel properly.

          The inverse problem is a much bigger problem (audio coming out after the video), and actually much more common. Most receivers do a good bit of sound processing nowadays, and some can do so much that they'll end up delaying the audio signal by some fraction of a second. Thing is, they don't delay the video signal noticeably and you wind up
        • The hi-fi community has been aware of this issue for quite some time. Those with "golden eyes and ears" probably claim that they notice a 10ms delay between video and audio, so the advent of digital displays provoked a "I can't stand that stuff" response.

          In answer to your question, most midrange (in hi-fi circles, "midrange" generally means between $500 and $1000) and all high-end receivers and preprocessors designed for home theater use will have an adjustable audio delay. I'm not sure how far this has p

    • 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.

      • Re:why do companies do this? (Score:5, Informative)

        by karnal ( 22275 ) on Friday April 23, 2004 @02:13PM (#8952977)
        You'll probably find that the "delay" on most receivers actually refers to the delay in putting audio through the rear channel, thus creating more of a "surround" effect if you have to sit in line with the rears.

        See, to get a sweet spot in a home theatre set up (wish I had room for a sweet spot in mine) is to set the rears equidistant from your ears as the fronts are. Unfortunately, many room environments don't allow for this, so you can use the receiver to "delay" the rear signals by so many milliseconds to make the surround more convincing at close range.

    • Re:why do companies do this? (Score:5, Insightful)

      by rsmith-mac ( 639075 ) on Friday April 23, 2004 @01:40PM (#8952677)
      I really wouldn't call this a work-around; at the very least, there's a physical limit you have to deal with when it comes to pixel response of LCD panels, and you can only minimize the time needed to digitially process an image, you can't remove it. The fact of the matter is that audio has to be delayed in order to compensate for the greater complexity of video, there's nothing else you can do.

    • Audio vs Video processing (Score:4, Informative)

      by xswl0931 ( 562013 ) on Friday April 23, 2004 @01:40PM (#8952684)
      Audio and Video processing happens asynchronously, so I don't know how you can avoid this. You can set a time limit, but then you will limit the amount of processing that can occur which sacrifices audio or video quality. I have a Panasonic 42" Plasma that does internal scaling. This is slower than doing Dolby Digital decoding. My Anthem AVM20 processor has an audio delay feature where now my audio and video are back in sync. Receivers are getting this feature so eventually it'll be commonplace.

    • Re:why do companies do this? (Score:5, Insightful)

      by nacturation ( 646836 ) <nacturation@gmai l . c om> on Friday April 23, 2004 @01:42PM (#8952697) Journal
      So once again, another company is working around the problem instead of fixing it.

      One man's workaround is another man's fix. Here, the problem is that video lags the audio by a fraction of a second. So there's two solutions to this problem: play the video with less delay or play the audio with more delay. Adding delay to the audio costs close to $0 because it just needs to be buffered for the 60ms it takes for the video to be shown. Speeding up the video might double the cost of the display as you might need parallel video processors which break up the incoming signal by physical region. Or you might need to find a faster display technology which hasn't been invented yet.
      • 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.
    • For de-interlacing you need to get the second field before you can figure out what to display. So there is 1/30 second there (assumming you wait until the end of the second field before displaying the result of the first one, if you really can sync it up carefully you could get the delay down to 1/60 second).

      It does seem compensation is the only solution. But there is a problem: lots of high-end equipment produces the sound and sends it to the speaker without any intervention from the tv (ie the speakers a
      • Arbitrary audio delay would make a nice feature for high-end digital audio decoders.

        I had not thought about speed of sound before; it looks like just standing at the back of a large room can put you 1 frame out of sync. So much for those sound design people that think they need to sync everything to the quarter-frame :)

    • MPEG-2 Video and Audio (Score:4, Informative)

      by bsd4me ( 759597 ) on Friday April 23, 2004 @02:17PM (#8953011)

      I used to develop code for digital set-top boxes, and I can tell you that this is not a trivial problem.

      Because of the way MPEG-2 video works, there is an inherent delay in decoding (frame order in the bitstream isn't necesarily the display order because of the way P-frames and B-frames work.

      Audio is slaved to the video through the use of timestamps, but the audio and video frame boundaries don't line up.

      I'm not sure if the problem is really lip-sync delay, but building in enough buffering to account for video delay while not glitching audio.

      Most people don't notice minor video problems, like repeating or dropping a frame, but they will hear lots of little audio glitches. Also, when a hardware audio decoder runs dry, you usually get a really bad artifact (it sound like stepping on a squealing mouse), and it takes 2 to 4 frames of audio to resync.

  • "What is that you say?" (Score:5, Funny)

    by Neil Blender ( 555885 ) <neilblender@gmail.com> on Friday April 23, 2004 @01:31PM (#8952569)
    "Let's Fight!"

    <mouth keeps moving for several seconds>

    Oh, wait. Those kung foo movies were always like that.

  • Big deal... (Score:4, Funny)

    by tinrobot ( 314936 ) on Friday April 23, 2004 @01:31PM (#8952573)
    I only watch 1960's Italian westerns and old Godzilla movies. Who knows, it might actually help.

  • Audio Delay (Score:4, Insightful)

    by 455 ( 718431 ) on Friday April 23, 2004 @01:34PM (#8952603)
    What good is building an audio delay if your sound goes through other components (ie. Big amp)? Wouldn't the sound then still be off? These people should be working to increase the processing technology, not slowing down the audio tech.

    booo I say

  • This could be fun. (Score:3, Funny)

    by dawg ball ( 773621 ) on Friday April 23, 2004 @01:34PM (#8952611) Homepage
    The audio delay should be user configurable. We could turn boring stuff into something that's really funny. Almost as good as playing the old VHS backwards!

  • This will hurt video games (Score:5, Insightful)

    by tepples ( 727027 ) * <tepplesNO@SPAMgmail.com> on Friday April 23, 2004 @01:36PM (#8952629) Homepage Journal

    Video games depend on low latency between input (at the gamepad) and output (at the CRT and speakers). Video game systems manufactured for sale in the United States after 2006 will include some sort of digital TV output. These digital TV sets introduce a significant latency into the chain. So what will happen?

    • What will happen? No one will be able to beat Square's "Legend of Dragoon" .... oh wait
      • ARGH! Legend of Dragoon wasn't made by Square! Now that I've gotten that out of the way, well, I don't think it would effect videogames much. I mean, the audio delay wouldn't - that would be slowing down the audio to match the video. If anything hurt videogames, it would be the laggy video.

    • Re:This will hurt video games (Score:5, Funny)

      by zulux ( 112259 ) on Friday April 23, 2004 @01:54PM (#8952815) Homepage Journal
      So what will happen?

      It's not a problem! It'll just make Halo play like Myst.

    • 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.
    • Comment removed based on user account deletion
    • Video games depend on low latency between input (at the gamepad) and output (at the CRT and speakers). Video game systems manufactured for sale in the United States after 2006 will include some sort of digital TV output. These digital TV sets introduce a significant latency into the chain. So what will happen?

      Some of the fancy processing, such as 3:2 pulldown and deinterlacing, is only applicable to 480i signals. HDTVs generally disable a lot of that stuff with ED/HD signals. All of the current videogame
      • "Some of the fancy processing, such as 3:2 pulldown and deinterlacing, is only applicable to 480i signals."

        480i? What game system are you playing? I don't know about the PS2, but the Xbox outputs at 480p, and some (very few) games do support 1080i.

  • HDTV formats (Score:2, Interesting)

    by Genjurosan ( 601032 )
    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.

  • So much for live tv (Score:3, Funny)

    by BMonger ( 68213 ) on Friday April 23, 2004 @01:37PM (#8952639)
    So that means that a plasma TV is going to be 60 ms behind my neighbors old CRT TV? No thanks. I need my reality TV as it comes, not later than my friends...
  • sorry for not being up on my TV technologies but i was planning on gettitng a DLP TV soon and was wondering if they were effected?

    is there a way i can test in the store?

  • just put your speakers 60 feet away (Score:5, Funny)

    by coult ( 200316 ) on Friday April 23, 2004 @01:39PM (#8952663)
    But, there is the delay from the sound traveling from the speaker to your ear (roughly 1 millisecond per foot of distance traveled). So one solution is simply to put the speakers about 60 feet away.

  • Analog Signal Buffering (Score:2, Interesting)

    by 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.

  • Workaround exists! (Score:5, Funny)

    by 3Suns ( 250606 ) on Friday April 23, 2004 @01:43PM (#8952699) Homepage
    There's no reason to build expensive circuitry to correct the problem. You can use the laws of nature to resynch your video!

    For a video lag of 60 milliseconds, you only need to step back 20.4174 meters from your TV before the speed of sound will correct the synchronization problem.

  • The Neurochemical Fix (Score:5, Funny)

    by Scott Baio ( 549373 ) on Friday April 23, 2004 @01:43PM (#8952702) Homepage Journal
    I find that if I get ever so slightly drunk, the delay in my mental processing of the auditory information compensates nicely.
  • Thanks for the news! I was about to return all those old Toho Studio "Godzilla" movies I bought for my new TV because none of the words matched the lip-movements. Now I know why!
  • I'll have to take that Milli Vanili DVD back to the store.
  • Of course, to talk about lip sync -- which is about matching audio to the movement of human lips, or matching the movement of lips to audio -- is misleading. This article is about video that is already lip-synced, but which suffers from a delay inherent in the viewing mechanism.

    The problem applies equally well to any other kind of video/audio synchronization that when out of whack will appear unnerving to the viewer; for example, gunshots; car explosions; doors slamming; the little high-tech bleeps made

  • Sucks for PCs, and on input too (Score:3, Interesting)

    by dbrower ( 114953 ) on Friday April 23, 2004 @01:45PM (#8952730) Journal
    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

    • 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 mu

  • I ran into that... (Score:5, Interesting)

    by JediTrainer ( 314273 ) on Friday April 23, 2004 @01:47PM (#8952751)
    ...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?

    • Not originally from this planet, eh? (Score:4, Funny)

      by Kozar_The_Malignant ( 738483 ) on Friday April 23, 2004 @03:32PM (#8953952)

      >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?

      Dilbert: We have a serious flaw in our product that can be corrected with a cheap, quick swap-out of the Model 9 Frammish Board with the Model 9A. You want me to recall all 495,000 units that have shipped to our value-added resellers and make the change, right? Remember, I told you about this six months before any of these units shipped.

      Pointy-Haired Boss: Noooo. Let's wait and see how many retail customers call and complain. We'll send some minimum wage guy out to swap out the card for the one's that somehow manage to call us.
  • A cheap ATI TV Wonder VE (Value Edition) - mono sound, and the tv gets out of sync.

    I only use it for watching hockey [www.cbc.ca], so it doesn't really matter.

    The weird thing is that the tv card just passes the audio through to the sound card (a built-in on the MB).
  • Some receivers like the Denon 3802 and upwards, are aware of these issues. They allow you to dial in delay so that you can sync with TV.

    Just my 2 cents ...

  • Well, you see, these displays are SO BIG... (Score:5, Funny)

    by dpbsmith ( 263124 ) on Friday April 23, 2004 @01:52PM (#8952792) Homepage
    ...you can just view them from sixty feet away and the video delay will exactly compensate for the speed-of-sound delay. No problem.

    And if you can afford one, you probably have a living room that big.

  • Sure it's the display device? (Score:4, Interesting)

    by ... James ... ( 33917 ) on Friday April 23, 2004 @01:52PM (#8952799)
    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.

  • Excuses, excuses (Score:4, Funny)

    by JediTrainer ( 314273 ) on Friday April 23, 2004 @01:53PM (#8952802)
    Any bets that they're just trying to build in delays to prevent more 'wardrobe malfunction' fiascos?

    My hunch is that they delayed the video on purpose, but forgot to touch the audio.

    :)
  • Beyond the great video resolution of HDTV, it also supports Dolby Digital 5.1 surround sound. So, most people use their stereo receiver for the audio from HDTV broadcasts.

    I have a macro set up on my remote, so when I turn the TV on, it automatically turns my receiver on & switches to the right input. I haven't used the speakers in my TV in 3 years, so I'm not sure if it has a lip sync problem or not (probably not, because it supports all the ATSC formats natively.. it doesn't need to do the extra p

  • rewrote their software (Score:3, Informative)

    by phsdv ( 596873 ) on Friday April 23, 2004 @01:57PM (#8952842) Journal
    The digital video group I used to work for had to rewrite their 'kernel' of video software when they found out about this problem. This is already more than two years ago.

    The old way was to read in a frame into memory. An other HW block or processor would perform the next operation, by reading that frame, process it and store it into memory again. The whole chain could be quite long.

    This was not really a problem, they thought, because the audio was processed at the same time, and the delay was under full control of the soft and hardware.

    until someone tried to use an external audio path...

    As far as I know, they solved the problem, and the delay is minimal. And non existant if you route the audio over the same processor.

  • I've noticed it on regular TV lately.. its hard to catch, but its there..

    Seems to have started once my cable company went to digital...
  • Occasionally when I un-pause my Tivo, the audio and video don't line up exactly. It's one of those things you don't notice immediately, but it lends an air of sinister uneasiness to atmosphere of the show.

    Kind of like taking too much cough medicine before a job interview.

  • Very noticable example (Score:5, Funny)

    by entrager ( 567758 ) on Friday April 23, 2004 @02:01PM (#8952888)
    If anyone wants to see the real thing in action, just tune in to the Britney Spears concert that has been airing on ShowtimeHD. Her lips are definately out-of-sync with the music.
  • I was recently going through a list of I2C chips to mess around with on my BASIC Stamp. (One of the areas where the I2C protocol had some measure of success was in television.) I came across a chip, I want to say from Philips themselves, that could be used to introduce a sound delay to allow the video to be better sync'd to the video.

  • Real Problem... (Score:5, Interesting)

    by braddock ( 78796 ) on Friday April 23, 2004 @02:04PM (#8952907)
    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

    • It doesn't matter anymore if a customer is pissed off about the quality of your product, there are 99 other ones in line behind him.

      If you buy model X and it sucks, that won't stop me from purchasing X because nobody researches this stuff beforehand. I just go to the guy in the TV department and he points me to model X and I buy it.

      The market does nothing to punish poor quality.
  • What is the deal here? This is like a car maker shipping vehicles all over the country with brakes that don't work.

    This is an easily spotted problem and a simple fix.

    Sometimes I worry about all these "product engineers" working with what amounts to computer technology more and more. They often don't seem to understand what they are doing or how to work with the technology and end up doing a really bad job.

    Think someone who did a whiz-bang job on a satellite receiver in the early 90s being put on a projec
  • Just pick up one of these [jandr.com]. It's a Yamaha receiver, about $300, that allows you to adjust the audio to match the video and eliminate the problem! Adjustable from 0 to 100 ms.

    Whips out credit card......

  • Just sit back from the screen about 70 feet and the sound and lips will sync up just fine!

  • Britney (Score:4, Funny)

    by raider_red ( 156642 ) on Friday April 23, 2004 @02:21PM (#8953053) Journal
    I've seen this problem. I noticed it during the Britney Spears pay-per-view concert. Sometimes it seemed like her lips weren't even moving at all, but she was still singing.

  • "cheap processor" is a myth. (Score:5, Interesting)

    by Bender_ ( 179208 ) on Friday April 23, 2004 @02:22PM (#8953069) Journal
    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...

    • 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

  • Adding a fixed delay will not resolve the problem (Score:3, Interesting)

    by cyclocommuter ( 762131 ) on Friday April 23, 2004 @02:22PM (#8953074)
    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!

  • So much for "live" television (Score:3, Funny)

    by pmbuko ( 162438 ) <pmbuko@g m a il.com> on Friday April 23, 2004 @03:07PM (#8953606) Homepage
    I personally couldn't stand it if my neighbor (with a standard CRT television) found out who the big winner of American Idol was 60 milliseconds before I did!

  • Not specifically a plasma display problem. (Score:3, Informative)

    by PhilipPeake ( 711883 ) on Friday April 23, 2004 @03:10PM (#8953645)
    This problem really isn't specific to plasma displays, its inherent in the crappy digital TV standards. MPEG has two streams, audio and video. There are no sync indicators to lock the streams together, they just flow independently.

    Slow processors can significantly delay the generation of the output video. Not only that, but the amount of work the processor has to do, which depends on how many changes from frame to frame take place, will cause varying delays.

    The way the problem usually manifests itself is that the delta between video and audio gets biggere and bigger, the two slowly drift apart. The video is, of course, being backed up in memory. At some point it will run out of buffer capacity. The olde way of dealing with this was to just flush the buffer, which brings thing back into sync (for a while), but usually causes a nasty glitch in the video (blank screen for a few frames) in most cases.

    Newer techniques involve dropping frames, more of them as the buffer fills up.

    A good indicator that you are getting buffer overflow is when you change channel, then change back again and all is back in sync (for a while). This will have flushed the video stream buffer, and life will be good, untill it backs up again.

    Faster processors can deal with the overall data rate without having to resort to these extremes, but the inherent delay caused by having to buffer a frame (or more) to be able to decode the next (because we are dealing with frame deltas in MPEG) will still cause varying delays in the video.

    The real answer is to use adquate processing power, and to modify MPEG to insert timing marks into the video and audio streams, and allow the system to automatically and incrementally adjust the audio delay to keep it in sync with the video.

    Expect to see a squadron of flying pigs before this happens ...

    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?

    • 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 c

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