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Discussion Starter · #1 ·
I have been seeing a lot of threads on this forum about lip sync problems with the latest release of STB's. I originally thought this was just a Sony/CBS thing, but now have seen most of the brands and CBS, ABC, and FOX mentioned.


Does everyone have some kind of lip sync issue, or is this still just a Sony/CBS thing?



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Dave B.

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Discussion Starter · #2 ·
I guess the best way to find out the information is to answer 4 questions.


1) Are you seeing a lip sync problem?


2) What type of STB do you own?


3) What city are you getting OTA from?


4) What network and channel?


My answers are;


1) Yes


2) Sony HD100


3) Washington, DC


4) CBS (9.1) and a little on FOX (5.1)



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Dave B.

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My understanding was that this was more of a local station problem than an STB one.


1) Yes, I have the problem here and there, but not always;

2) DTC100

3) DFW

4) Primarily seen on NBC:

- On Leno after the commercial break following the monologue. I don't notice it before that.

- On the commercial breaks during the recent HDTV broadcast of the Mavericks/Jazz game. The sound during the game (real HDTV) seemed in sync, or at least the "bump" of the basketball occured at the same time the ball made impact; commercials (which were from a separate upconverted NTSC feed) were definitely out of sync.


Haven't noticed this problem at all on CBS, FOX, or ABC (which runs a very nice demo loop during the day).
 

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Discussion Starter · #5 ·
Joe,


Normally I would agree with you, but we know that just about every CBS station in the country has a lip sync problem with the Sony HD100. The Sony doesn't have the problem with other stations and CBS doesn't have the problem with other STBs. The exception to this is NYC and LA, but even LA had the problem until they did an upgrade on their encoder. I just wanted to see if other STB's were experiencing this with any of the other local affiliates.


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Dave B.

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I've had lip sync problems with directv and my old SONY receiver on and off for four years I've subscribed. I see it periodically on the new HD-100. Not so much Directv as OTA now on ABC and PBS. As it drifts on PBS, I just flip to another channel and back and all is fine until it "drifts" again. I agree with [email protected] It is a system "sync" problem.


I think that if the encoder/PSIP is not configured properly, these things can happen.


I am now convinced my local KING 5.3 break ups are caused by this using the HD-100 . It is awfully coincidental that the KING break ups on 5.3 (emphasis on the .3) happen on my PBS channel but only on 9.2 and 9.3.


Is it not fun being a Beta tester?


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[This message has been edited by Babula (edited 05-10-2001).]
 

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Yes

Dish 6000

Portland, OR

ABC, CBS, FOX (ABC is the worst, others intermittent)


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1) yes, but only here and there

2) Panasonic TU-HDS20

3) Chicago

4) ABC, but, the Frampton concert segment on the DirectTV HD loop is horribly out of synch, but, the Springsteen show was not out of synch.

 

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Dave, you probably saw this on my other post. I have no more lip sync on any channel now that WUSA has fixed the problem. It must not have been the Sony (directly) but the "out of limits" feed from WUSA, which the Sony box could not adjust to.
 

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1. none

2. hd100

3. seattle

4. none
 

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1) Yes -- occasionally


2) Telemann HiPix card


3) Los Angeles


4) All that I watch -- CBS, ABC, PBS mostly.


Problems will come and go even within the same broadcast.
 

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Discussion Starter · #12 ·
Its starting to look like this is pretty much a universal problem with most STB's to some extent. The only exception seems to be the Samsung SIR-T150 which is, I believe, an OTA only unit.


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Dave B.

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In light of all the posted information, I would speculate that the majority of audio sync problems are based at either the network or local broadcaster.


I say this because if it was simply the stb, we would see a nationwide problem with consistent symptoms. I believe this could well be the case with the Sony, but based on past history, all the other instances have been resolved (over time, to be sure) by either the network itself, or local DTV stations changing how their audio encoder functions.


So to answer the original question, no, all stb's do not have problems with lip sync. This would imply a design or function problem with the stb's.


But there is a sporadic problem with compatibility between DTV broadcasts and most, if not all stb's. Remember that we are in the very early stages of DTV broadcasting and issues like this are bound to occur, or look at it this way: This is just another chapter in the plight of the early DTV adaptor.


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Discussion Starter · #14 ·
You have convinced me that it is a broadcasting problem and not an issue with the STB. The Sony might be an exception to that, however as Jimmy states above, WUSA is now working fine. This happened just a few days after Bob Ross said he would call them to see if he could get the problem resolved. I still wonder why, if it was a WUSA problem, the Sony was the only STB that it effected.


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Dave B.

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Hi All


I cut this from over in the programming forum. It is a good explanation of what is going on.


Why does it happen more with the CBS O&O's? We bought all the same encoders and the default settings is NO "B" frames. This encoder has more than 50% market share. This only effects the one STB and we do not know why.


-=-=-=-=-=-


During the MPEG 2 video compression process different types of "frames" are used.

Every Group Of Pictures (G.O.P.s) begin with an "anchor" frame. Refereed to as an I frame. The I frame has all of the data necessary to create a picture. After an I frame is transmitted. It is not necessary to transmit all of that information over again to create the next frame, most of the information would be reundant.

The next frame can be the data that is different from frame 1 to frame 2. The "difference information" or "predicted" information is called a P frame. Typically it has 20% of the data as an I frame. One more frame type can be used. It is called a "B" frame. B frames are Bi-directional. They can contain information about the previous frame or the next frame. (frames are not always sent in chronological order)

A "B" frame is usually information that instructs the encoder where to move blocks of pixels within a frame.

A car moving past a stationary wall could be 1 "I" frame and a bunch of "B" frames telling the encoder where to move the same color pixels. "B" frames can contain only 5% of the data of an "I" frame. That is how we can squeeze 1.5 gigabit/second of data into a 19.4 megabit/second channel.


OK confused yet??? How does this effect certain STBs???


Some encoder manufacturers, avoid "B" frames. It is a video quality issue. With out the B frames, the data rate through the set top box is a little higher. 1080i is the most data intense HDTV format. When the subject matter ORIGINATES as 1080i the data rate is at a maximum. (there is less redundant information)


Some boxes can not keep up with the higher data rate, their data buffers get overloaded.


WFOR-DT has enabled at least 1 "B" frame per GOP. This we are told is supposed to take care of the Lipsync problems and some other issues with a select few boxes.


=-=-=-=-=-=--=-=-=-=-


Bob


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One other problem so far not mentioned is the problem ABC sometimes has with the 5.1 channel audio. The network plays back the stereo audio from the D5 machine that is playing the pictures. The 5.1 channel audio is played from a separate digital audio tape that is supposed to held in sync with the video/stereo playback. This time lock has sometimes been off. We have seen audio lip sync problems with 5.1 channel sound a number of times incoming to the station from ABC.


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Discussion Starter · #17 ·
Engine-Ear,


I'm sure Bob is refering to the Sony HD100. That's the STB that has a sync problem with CBS stations across the country.


Just another question about your statement -

"However it seems, from the analysis he posted, that at least one major lip-sync issue is caused by the inability of the MPEG2 decoder in that STB to "keep up" with the transmitted frame structure in the data stream."


If that were the case, wouldn't it have trouble keeping up with all 1080i content? I don't know if the same technology is used on HBO HD, but it never has a problem. Niether does NBC, PBS or the WHD channel that broadcasts here in the DC area. Ofr course, we can't compare it to FOX or ABC since thay don't do 1080i.


Also, Bob says he didn't do anything but have someone make a phone call, but after he did, the problem on WUSA in DC went away. Hmmmmm....



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Dave B.

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My answers are;


1) For a few days, but was fixed yesterday 05/14. The station went off the air in the afternoon and then came back on with the lip sync problem fixed.


2) Mits HD500/400


3) Washington, DC


4) NBC (4.1) only, all other stations never had a problem


 

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Discussion Starter · #19 ·
If that is the case, at least it can be fixed with a OS download via DTV. I just don't want to have to send the box back to Sony to have these things resolved. I can imagine everyone sending theirs in at the same time and what a logistical nightmare that would be.


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Hi All,

Yes I have a lip-sync problem.

STB - Mitsubishi SR-HD500(HDR)

Station WRAL Raliegh

Condition. When receiver to switch to digital input there is a lip sync problem. Problem goes away with analog switch on.

1) This does not happen with network feeds of HDTV.

2) This does not happen with HDTV feeds from WRAL.

3) It only happens when WRAL upconverts reqular NTSC programming to 1080i(i.e. CBS evening Newes, ETC).


I have not contracted WRAL as of yet. I am currently collecting data. After I am able to repeat the problem I will give WRAL a call.


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