DBSTalk Forum banner
Status
Not open for further replies.
1 - 17 of 17 Posts

·
Godfather
Joined
·
417 Posts
Discussion Starter · #1 ·
I've seen a lot of postings about lip sync. I wanted to write a letter to explain to those who are interested why there are so many lipsync problems with HD.

First off, I am the IT Supervisor at a PBS station in Ohio. We run 2 television stations. Each of those stations are running 4 standard definition channels during the daytime on their digital channels. So we are programming and managing 8 discrete programming streams. You can imagine the issues we've had to conquer. At night, we run one 1080i HD channel and one 480i SD channel on each station. Because of the number of computers involved in digital television, I do as much of the engineering work as the chief engineer does.

Lipsync problems in HD mostly result from the fact that the video and audio are processed discretely from one another and the stations are not making the effort to configure their equipment to make up for the delay. This is escpecially true if a station runs Dolby 5.1 audio. In order to process Dolby 5.1 audio at our stations, the audio runs through either 3 or 4 boxes. When we first set up our HD channel, we were seeing major lipsync issues. After some trial and error, we finally contacted Dolby, who told us that there is about a 200ms delay in the processing (Yes! Almost 1/4 of a second!). We configured our system to account for this delay which took care of the lip sync problem in our digital stations.

So that's some of the issues a content provider has to deal with. However, DirecTV should be able to sort these issues out with some troubleshooting steps. I'm going to use ESPN HD as an example, because it seems to be the worst lipsync offender I see on the satellite:
1) Is the video and audio in sync before it goes into whatever box sends it to DirecTV?
2) Is the video and audio in sync once DirevTV receives it from ESPN?

Okay, there they've taken care of that side. Now it gets more complex dealing with the end user's equipment.

Don't forget the video and audio signals are compressed on the satellite. What kind of delay is there for the chips in the receiver to decode the audio and video? They have to adjust the receiver for that delay.

Also, if you are using HDMI or optical cable, the decoding delays in your television set and home theater system come into play. This is still a compressed digital signal running on both of these mediums that has to be uncompressed and convertered to analog audio. For example, I use the HDMI output of the HR20 to get the signal to my TV. From there, I use the optical output of my television to run my home theater system. So here's what has to happen. My television has to uncompress and decode the HDMI signal and show it on the television. It then has to take the audio portion, reencode it for the optical cable, convert it from digital to optical output and send it accross the cable. Now, my home theater system has to convert the optical to digital, uncompress it and convert it to analog audio.

I think now you can start to see how lipsync problems can happen. Also, it can be fairly hard to detect where the issue lies. But I hope this also makes you understand why a lot of people tell you to check the analog outputs of the receiver. These are immediately converted to analog directly out of the satellite receiver and leave the least chance for additional delays to be introduced to the signal.

There are probably a thousand more little intricacies that I could explain which could also contribute to the problem and I'm sure other posters will fill in the details.
 

·
AllStar
Joined
·
63 Posts
This is why it is important to get a good audio receiver which can let you build in delays in the audio or video to correct these problems.
 

·
AllStar
Joined
·
50 Posts
jodavis said:
This is why it is important to get a good audio receiver which can let you build in delays in the audio or video to correct these problems.
The "good" ones only seem to let you delay the audio. That's fine for compensating for things like deinterlacers, line doublers, LCD or plasma built-in delays (see http://www.audioholics.com/techtips/specsformats/AV_lip_sync_delay.html for instance), but on many of the mis-synced HD programs I've seen over HR20 the audio is already delayed.

I've not seen a receiver that lets you delay the video. Besides, it varys so much from channel to channel, even show to show and day to day, that it'd be a pain to set for each thing I watch.
 

·
Godfather
Joined
·
417 Posts
Discussion Starter · #5 ·
ExUltimateTV said:
... but on many of the mis-synced HD programs I've seen over HR20 the audio is already delayed.

I've not seen a receiver that lets you delay the video. Besides, it varys so much from channel to channel, even show to show and day to day, that it'd be a pain to set for each thing I watch.
Agreed! All of the lip sync problems I see on my HR-20 involve the video being ahead of the audio, which you are correct that a home theater system will not compensate for this.
 

·
Icon
Joined
·
770 Posts
marty45714 said:
For example, I use the HDMI output of the HR20 to get the signal to my TV. From there, I use the optical output of my television to run my home theater system.
I was wondering why you run the optical audio from your HDTV back to your receiver after using HDMI to get it to your TV. Why wouldn't you just run the optical audio from the HR20 directly to your receiver?
 

·
Godfather
Joined
·
417 Posts
Discussion Starter · #7 ·
I have 2 HR-20's. Both are hooked up via HDMI to the television. I want to listen to whatever is playing through the TV at the time.

TomF said:
I was wondering why you run the optical audio from your HDTV back to your receiver after using HDMI to get it to your TV. Why wouldn't you just run the optical audio from the HR20 directly to your receiver?
 

·
Registered
Joined
·
32,456 Posts
marty45714 said:
I've seen a lot of postings about lip sync. I wanted to write a letter to explain to those who are interested why there are so many lipsync problems with HD.
..........
There are probably a thousand more little intricacies that I could explain which could also contribute to the problem and I'm sure other posters will fill in the details.
Thanks for taking the time to share this. As you have pointed out, there's only so much D*TV can do about lipsync, and there's only so much an end user can do about it as well (even those of us with receiver audio delay options).

This also illustrates that the content providers have an obligation to do their part.

In the end, this is yet another potential "garbage in, garbage out" scenario.
 

·
AllStar
Joined
·
58 Posts
marty45714 said:
I have 2 HR-20's. Both are hooked up via HDMI to the television. I want to listen to whatever is playing through the TV at the time.
A receiver should handle this. I have an HR20 as well as a Sony DVD Changer currently setup in my living room. I have both connected to my Sony 60A2000 TV via HDMI and have digital audio going into my Marantz receiver. I use a Harmony remote which changes both the TV input selected on the TV and audio source on the receiver when I select a different activity.

If my older receiver accepted HDMI inputs I would not nee the digital audio inputs and I could run just one HDMI cable to the TV but it's not a big deal until I want to add another video source.

My point is that most receivers should accept audio from multiple sources and switch between them. I am curious why you are going the route you are going with this setup. Maybe your receiver is different than what I would imagine?
 

·
Legend
Joined
·
148 Posts
marty,
Are you running with PBS ACE?
I work in Albany and we were the first to go full with ACE about 18 months ago.
We are just about to change out our encoders so we will have to see if there is any difference then but until now we haven't had any lip sync problems.
After your dolby adjustments do you now see any difference between OTA and D*?
I have been watching OTA before and after HR20.
Side note that now with ox11 my OTA signal strength was strongest with PBS in the market although close with other channels but now with the new software it is still around 80% but CBS and ABC are now hitting 100%.
What is more interesting is that we have a community tower so we are all transmitting from the same place.
Aaaahhh engineering:)
 

·
Godfather
Joined
·
417 Posts
Discussion Starter · #12 ·
I want to use optical. I only have one optical input on my home theater. I have no hdmi input on the home theather. Hence, this is the best setup. Trust me, I do this stuff for a living. This is the best for my setup.;)

bobsloop said:
A receiver should handle this. I have an HR20 as well as a Sony DVD Changer currently setup in my living room. I have both connected to my Sony 60A2000 TV via HDMI and have digital audio going into my Marantz receiver. I use a Harmony remote which changes both the TV input selected on the TV and audio source on the receiver when I select a different activity.

If my older receiver accepted HDMI inputs I would not nee the digital audio inputs and I could run just one HDMI cable to the TV but it's not a big deal until I want to add another video source.

My point is that most receivers should accept audio from multiple sources and switch between them. I am curious why you are going the route you are going with this setup. Maybe your receiver is different than what I would imagine?
 

·
Mentor
Joined
·
46 Posts
marty45714 said:
Agreed! All of the lip sync problems I see on my HR-20 involve the video being ahead of the audio, which you are correct that a home theater system will not compensate for this.
This is fantastic information and makes things much more understood from my standpoint. Here's my question. I receive my local HDs from DTV. I am in the Philadelphia market and I have no problems with lip sync issues except for Channel 10 NBC. Who should I be complaining to about this? DTV or NBC Philadelphia?
 

·
Godfather
Joined
·
417 Posts
Discussion Starter · #14 ·
This is real easy to determine! Find a place to view the OTA signal with an antenna. This will show you what is coming from the station. If the lip sync is messed up, call the station and talk to the chief engineer.

HateComCrap said:
This is fantastic information and makes things much more understood from my standpoint. Here's my question. I receive my local HDs from DTV. I am in the Philadelphia market and I have no problems with lip sync issues except for Channel 10 NBC. Who should I be complaining to about this? DTV or NBC Philadelphia?
 

·
Mentor
Joined
·
46 Posts
marty45714 said:
This is real easy to determine! Find a place to view the OTA signal with an antenna. This will show you what is coming from the station. If the lip sync is messed up, call the station and talk to the chief engineer.
So that brings up another question that I have. I currently do not have an OTA antenna cause my locals are all coming in via sat. Is there any advantage to hooking up an OTA antenna. Will this also give me additional HD channels that I may not be receiving from sat. My dish is currently mounted to the side of my house....would I be able to attach an OTA antenna to it or does it really need to be on the roof or in the attic. This is all new to me so bear with me. Thanks in advance.
 

·
Cutting Edge: ECHELON '08
Joined
·
4,107 Posts
HateComCrap said:
So that brings up another question that I have. I currently do not have an OTA antenna cause my locals are all coming in via sat.
I think that someone has not told you the truth.

Check this link to see how many local HD channels you really get:

HDTV Magazine HD Local Channel Listing and Map

Antennaweb.org is good too but they often miss up to half of your channels.

You may be amazed at everything you are missing.

- Craig
 

·
AllStar
Joined
·
92 Posts
Milominderbinder2 said:
I think that someone has not told you the truth.

Check this link to see how many local HD channels you really get:

HDTV Magazine HD Local Channel Listing and Map

Antennaweb.org is good too but they often miss up to half of your channels.

You may be amazed at everything you are missing.

- Craig
I looked at the chart but unless I'm missing something, it does not distinquish between standard digital and HD. For example, Portland, Oregon - I beleive we get only channel 8 OTA in HD - NBC - at least that's what my HR20 is set to - yet it lists 8.1, 8.2 etc. and, again, I can't tell SD vs. HD?

comments?
 
1 - 17 of 17 Posts
Status
Not open for further replies.
Top