Loose Lips Sync TVs - AVS Forum
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post #1 of 13 Old 06-20-2014, 03:38 PM - Thread Starter
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Loose Lips Sync TVs



Media-technology consultant Paul Briscoe returns to talk about more SMPTE standardization activities, including the vexing problem of lip sync and how it came about, human perceptual issues, current solutions, the impending standard that addresses the lip-sync problem neatly and elegantly, SMPTE's suite of flat-panel documents, UHDTV screen size and its relation to frame rate, electro-optical transfer functions (EOTFs), SMPTE's study group on the entire high dynamic-range ecosystem, coding of tactile essence, answers to chat-room questions, and more.


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post #2 of 13 Old 06-20-2014, 05:17 PM
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Scott I am glad you brought out the fact that HDR needs 10 bit panels and The coming 120 frames rate. The new panels coming out in 10 bit from Vizio(R Series) can they do a 120 frame rate? The R series panel, according to Vizio is able do a 120 refresh rate for gamers,is that the same as 120 frames rate?

Great Job Again!

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post #3 of 13 Old 06-20-2014, 07:31 PM
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I want to go on the record now for Smellavision

NO!

Great Episode.
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post #4 of 13 Old 06-20-2014, 08:39 PM
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Originally Posted by Woobieizer View Post
I want to go on the record now for Smellavision

NO!

Great Episode.
At America the Beautiful, shown in the Circle Vision 360 theater in Disneyland, there are a couple of scenes where in a large audience some people start sneezing when the aroma for that scene reaches them.

Before Smellavision comes to the home, I hope there is a way to block certain aromas to prevent allergic reactions, particularly life-threatening ones.

And, yes, great episode!

My very humble setup:
Man Cave:Vizio E500i-A1 "Smart TV" (50-in 1080p 120Hz LED/LCD, has Netflix app.), Blu-ray players (Sony BDP-S3100, old LG BD390), Roku (the original model: N1000), PC (Windows 7), Comcast Internet (25Mbps/5Mbps).
Bedroom:LG 32LV3400-UA TV (32-in 768p 60Hz LED/LCD), HD DVR (Motorola RNG200N), Xfinity Comcast cable (Digital Starter Package), DVD/VHS player.
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post #5 of 13 Old 06-20-2014, 10:14 PM
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post #6 of 13 Old 06-21-2014, 03:07 PM
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Another great thought provoking episode.

Interesting approach with signatures to maintain lip sync, but the implementations in the receive end will be interesting. If it's off, should it slowly slew to being correct or would it just pop in. Passing metadata through a transmission system is no small matter as existing equipment may need upgrading. Should this be included on a source basis, or just for a transmission path? What about frame synchronizers? While video is frame based and can either have a frame dropped or repeated, the audio can also be repeated in frame chunks or skewed to avoid discontinuities. How will that affect this system? How accurate is this system supposed to be in matching lip sync. All sounds good but the devil is in the details.

In professional circles the Valid test signal has become a de facto standard for checking lip sync on transmission paths which measures each audio channel separately to a resolution of 1ms. ABC TV uses this as a standard network test signal.


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Last edited by TVOD; 06-21-2014 at 07:27 PM.
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post #7 of 13 Old 06-21-2014, 07:55 PM
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Before Smellavision comes to the home, I hope there is a way to block certain aromas to prevent allergic reactions, particularly life-threatening ones.
Might come in handy for The Terrance and Phillip Show, and for Mr. Hankey.
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post #8 of 13 Old 06-22-2014, 02:12 AM
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Lots of good technical info in this episode. Thanks Scott

"Bring out yer dead!".."Wait I'm not dead yet!"..(Sound Austrian here) "WRONG !!" (You know what happens next..)
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post #9 of 13 Old 06-22-2014, 08:57 AM
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this was a nice information about lips sync issue in broadcast in the digital part. but what about lips sync issue with TVs input lag.
these "time stamps" can't fix sync issue with input lag and AVR.
it's nice that the AVR can match the audio to the video but the TV still got an input lag and it has to know his input lag which can change depending on settings. how are they going to fix this issue.
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post #10 of 13 Old 06-22-2014, 12:54 PM
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the TV still got an input lag and it has to know his input lag which can change depending on settings. how are they going to fix this issue.
I was thinking that too, but display delay stays consistent with a given setting. Rather than signatures, it would be nice with handshaking if the display conveyed its delay.


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post #11 of 13 Old 06-24-2014, 02:06 PM
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I was thinking that too, but display delay stays consistent with a given setting. Rather than signatures, it would be nice with handshaking if the display conveyed its delay.
It seems to me that display lag is dependent both on the settings of the display and the format of the content. I could be mistaken, but I seem to need different amounts of audio delay depending on whether the source is 480p, 720p, 1080i, or 1080p. I think I have also noticed it more with higher native framerates (e.g. 60 fps) than with lower ones (e.g. 24 fps) or possibly the other way around. This could just be issues with the lip sync in the source but, judging from the way my screen goes black for about a half second every time I switch from a 720p channel to a 1080i channel, I suspect that my TV has a noticeable amount of display lag in it and that the lag might just vary a good bit depending on how much upscaling and/or de-interlacing the TV has to do for a given format, even with the same TV settings.

The issue is that, again, we are separating the audio from the video when we use a surround sound system. And, as things are now, the audio isn't even being sent to the TV, so it is not possible to do another analysis after the video processing is complete but before the image is displayed. It seems there are three possible solutions for this...

1) Start passing the audio to the display before it is sent to the speakers and do one final analysis of lip sync in the TV after the video processing is done, but before the image is displayed. Adjust the lip sync one last time and use the audio return channel to tell the AVR when to play the audio. For this to work TV's would have to be compatible with all of the same audio formats used by your AVR in order to prevent your audio from being gimped. This would add to the cost of TV's since they would have to pay the licensing for all of those formats in order to ensure compatibility.

2) Do a better job of establishing and holding to a specific amount of display lag in a particular TV, regardless of the TV settings and the format of the content. Once you know what the highest amount of display lag will be for a given display for the worst possible combination of TV settings and content format, set that as the universal display lag and buffer everything else to match that. Once you have a constant display lag, all you would need to do is have the display report that to the AVR so it can automatically delay the audio by the correct amount, as TVOD suggested. This would ensure that whatever comes in, goes out as far as lip sync is involved. So, if the Blu-Ray player/AVR can do the finger print analysis and autocorrect the lip sync before the video signal leaves the AVR on the way to the display then everything should be in sync. The only place where you might need to disable this feature would be for gaming, since reduced lag is more important than proper AV-sync.

3) Stop using a TV to process video. Use an external video processor that handles all of the video processing and the lip syncing in coordination with the AVR. At this point your TV is nothing more than a monitor. The problem with this solution is the cost of the additional video processor.

Solution #2 would be the cheapest for the consumer. Solution #1 is probably unlikely any time soon, but may come about as a result of streaming and the fact that they want the TV's to be able to use their own built-in streaming apps, which means the TV's have to support all of those audio formats for an optimal experience anyways. Solution #3 is the most expensive, but it's main advantage is that you can pretty much do that with today's equipment if you are willing to pay for it.

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post #12 of 13 Old 06-24-2014, 02:47 PM
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The display shouldn't need to measure its delay as they should be consistent and known for each given mode. If the AV Receiver is passing the video to the display, I think a method for the display to pass back to the receiver what its current delay is would allow the receiver to compensate. A one byte payload would suffice.


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post #13 of 13 Old 06-24-2014, 03:35 PM
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The display shouldn't need to measure its delay as they should be consistent and known for each given mode. If the AV Receiver is passing the video to the display, I think a method for the display to pass back to the receiver what its current delay is would allow the receiver to compensate. A one byte payload would suffice.
That's basically what I was trying to describe in solution #2 . The key is that the display has to actually maintain a constant display lag regardless of what type of content it is receiving. If it takes 40 ms for it to de-interlace and process 1080i vs. 60 ms to upscale and process 720p vs. 20 ms to process 1080p when the TV is in the same display mode then the TV should buffer whatever it is receiving to produce a 60 ms display lag and report that to the AVR. This would eliminate the variation caused by different content formats and the differing amount of processing required for it. If they want to have variable amounts of display lag based only upon TV settings and report the proper display lag for that setting to the AVR then that is fine too. At the very least, they would need a Game Mode that uses the least amount of processing possible and disregards lip-sync errors in order to reduce display lag as much as possible for that particular mode.
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