Audio out of sync

[JohnDH]

I'm new to this forum and I'm hoping someone can help out with my problem.

I use an EyeTV 500 in Mac OS X to view HD, and I've noticed that the the audio for NBC lags behind the video by about 200ms. I don't have an HDTV to compare with my computer setup, and due to not seeing other threads about this, I'm guessing the problem is not something that many other people are dealing with.

This may only be for certain shows like Conan O'Brien. (This is the only show on NBC I watch regularly.)

Other channels (CBS etc.) don't have this problem for me.

Is there something that can be done to solve this? A big thanks to anyone who can help out.

[DublinDoodah]

No, you are not alone. If you look through some of the threads here, you'll see that a WCMH engineer has been gracious enough to contribute to this forum. He reports that he's attempted to sync the sound, but I still see problems with it from time to time.

I find it ironic that for all the advantages that the new digital technology is supposed to provide, we have to tolerate many new annoyances like inconsistent volume and out-of-sync audio/video.

[Captain_Rob]

Audio and video sync issues are usually the result of the video be reprocessed multiple times between the source and the actual display. For example, the local broadcast station may add their logo ("bug") and/or information crawlers to the video. Video delays can also happen in the home if the STB or HDTV must up convert or down convert the signal. For example, if the HDTV has a 720p native resolution, but the program is being broadcast in 480i or 1080i, either the STB or HDTV must convert the video to 720p. If improperly setup, a 480i program may be up-converted to 1080i by the STB, and then down-converted to 720p by the HDTV. Each of these steps can delay the video by a frame or two due to the processing time it takes for each step. If the audio stream is not somehow delayed by the same amount of time, the audio will end up being ahead of the video. Because of this, some high-end equipment contains audio delay circuitry, which can also over compensate and cause the audio to lag the video. Due to the various programming sources and processing equipment, I understand how keeping the audio in sync can be a challenge. IMHO, this was an oversight in the DTV specifications, and they should have included some kind of timing marks in the audio and video streams to keep everything in sync.

[JohnDH]

Thanks for your input guys. Very informative. I must have missed the thread where this was brought up before, sorry about that.

I did see that a WCMH engineer posts in this forum, which is very nice of him. Perhaps he can weigh in on this thread at some point.

As I said, I really only watch Conan O'Brien on NBC so I can't say much about other shows, but it seems for Conan it is always (or at least the great majority of the time) out of sync. I checked yesterday and the local news appeared to be ok. So I guess it may depend on the show.

It's strange how just 200ms can change the viewing experience. Things such as mouths moving without voice for that split second, and bands playing - drums not matching the sounds etc. can really take the viewer out of the experience. Hopefully something can be done about this at some point. I sympathize with people who have to try and trouble shoot this kind of quirky technology.

[kevinbuckeye]

Has anyone else noticed NBC being way out of sync the last few days. I noticed it on Leno the other night and the West Wing tonight.

[nakedeye]

yes i have noticed

[JohnDH]

Hi all, I thought I'd revisit this thread (it's been about five months) to see if there would be any positive news. Sadly there doesn't seem to be.

I don't like to complain, but I really wish the Late Night with Conan O'Brien sync trouble could be solved. I've never seen the HD signal in sync, not once. :(

It really takes the impact out of seeing a good band play when what they're doing with their instruments doesn't seem to make any sense whatsoever. Again, the audio/video only seems to be 100 or 200 ms out of sync, but it can make a world of difference.

Could this be caused by my setup? Or is this the same for everyone?

If it's the same everywhere, I'd really like to know if we can expect this problem to go away any time soon.

Thanks for reading this.

[rossl]

Watching the NBC pre-season football on Sunday night August 6, I noticed that the pre-game show before 8:00 was badly out of sync. More than 200ms, maybe a third of a second. It seemed to be better during the game.

[festivus]

Any time that I tune in to ch 714 (TWC NBCHD) or use my OTA receiver, NBC4's audio is out of sync with the video. I tried my OTA just to make sure it wasn't TWC doing something odd. NBC4 broadcasts in 1080i which is the native resolution on my TV, so I don't think it's a conversion issue. It is very annoying. I don't have this issue with any other channels. Not even with ABC where my OTA receiver must convert 720P to 1080i.

[NBC4ENG]

Sorry I haven't been active for awhile. I've had a few health problems. That said, I need some info. Is the delay occuring all the time, even on our news, or is it only on the network HD feeds? This is very important to distinguish. There are two different paths these signals take. I can alter both. Some of you mention 200ms delay. Are you measuring this and how are you measuring this. Can this be an educated guess? Whatever, let me know, give me a phone number of a forum member you want me to call during any show and I'll screw with the timing for you. Let's get this resolved ASAP. Delegate someone from your group to represent you and give me a call on my cell at 205-4028. Thanks.

[Timcredible]

Shaun,

Good to have you back. Hope you're feeling better. What I've seen is that the high-def shows audio is visibly behind the video. I don't watch non-hd content on nbc, so I can't say if the local news has the same issue. If I remember correctly, my wife watches Ellen and a judge show in the afternoon, and I don't remember seeing the problem then. Although I just checked last comic standing and the audio is just barely off, maybe .05 seconds? I would agree with the .2 seconds on the hd content (that being a very unscientific estimate). I don't think there's any hd content tonight on nbc, but I'll be home tomorrow night if you want to call during Earl or the Office - I'll send you a PM with my phone number.

[JohnDH]

Hi Shaun, thanks for replying so promptly. I'm sorry to hear of your health problems.

In response to your queries:

1. "Is the delay occurring all the time, even on our news, or is it only on the network HD feeds?"

It's hard for me to say, as the only show I really watch in HD (network or local) is Late Night, but that at least hasn't ever been synced correctly - the audio always coming after the video.

I just turned NBC on to check, and Last Comic Standing seemed to be ok. I can keep checking other shows. Sorry I can't be of more help on this right now.


2. "Some of you mention 200ms delay. Are you measuring this and how are you measuring this. Can this be an educated guess?"

I don't have an HDTV yet, so all my HD viewing is on a computer. I sometimes record shows or segments and therefor can play around with the sync time in software. But even with this it's hard for me to say exactly how much the sync time is off. My best guess is 100 - 200 ms.

I don't know if this would be proper or even helpful, but what I could do is upload a short (50MB) HD clip of Late Night I have, and send you the link. You may be more able than me to accurately tell how far the sync is off.

[NBC4ENG]

At this time I have pulled out all delays on the HD Network side. The only delay would be due to a video frame sync on the HD receiver. I will stay tonight and listen on the HD net shows. If you can pay close attention to the surround sound. I want to make sure you do not hear any echos in the left and right rear channels. If we are OK there, I'll proceed to tweak the video timing from the receiver to match the audio. I'll try not to add any delay in the audio chain. I'm able to slide video timing one way or the other to match up the audio. This isn't scientific what I'm doing. I can only monitor the surround while we are on the air. Each time I make an adjustment to the video, a hit will occur in the picture until relock occurs. Once you are happy, I'll store the delay and we'll see what happens on further shows. Thanks.

[Timcredible]

i'll keep editing this post during the evening to report on this:

5:40pm - vol of america commercial - looks perfect
6:56pm - national news - looks like audio behind video, maybe .1 or .2 seconds
7:03pm - extra - looks like audio behind video, same as news
8:00pm - earl - i've seen you changing things, there was one time in there that everything looked sync'd correctly, then the time when the video was messed up, and now a commercial (8:09pm).
8:18pm - earl - the last segment of earl had the audio behind the video
8:34pm - office - looks really close. for some reason, it doesn't look quite right, but maybe i'm overanalyzing.

[NBC4ENG]

TIMCREDIBLE call me at 205 4028 Let's line it up

[NBC4ENG]

I've set timing as best as I can. No one has called me with any comments. Unfortunately, I live 60 miles from here and I have to go. To me, it's dead on. Let me know. Regards

[Timcredible]

It looks good to me. If others notice anything, please post it.

[JohnDH]

I just spent the last 20 minutes in syncing software playing around with clips from Thursday's Late Night with Conan O'Brien.

After listening to four different clips over and over again I've decided on a audio video difference of 167ms. The program I use goes in 33ms increments, so my choices were 133 - 167 - 200 etc. All three of those were looking good to me, making it a hard choice. (It's tough to be exact in this with the video playing at normal speed.) But since 167 is in the middle I think this would be the best of the three.

So that means at least from my tests the audio is coming 167ms behind the video. Hope this helps. I can run the tests again with the Friday show.

Thanks for your time Shaun.

[NBC4ENG]

Don't mean to belabor this, but audio behind the video just can't be in our current setup. Audio ahead of the video I can see occuring. The audio path has no delay at all, at present. The video path is going thru a frame sync which will delay the picture by 1 frame. Transmission rate is 30 frames per second. 1 frame is 1/30 of a second or 33ms of delay. Switching between the upconverted feed and the network HD feed I can see no difference in timing. I can't speak for the network feed point timing, but locally we are extremely close. I continue to keep an eye on the issue. Regards.

[velvet396]

This is great that there's someone from WCMH listening!

From time to time I have noticed that Conan's HD broadcast is out of sync, namely that the audio is ahead of the video. However this hasn't occurred recently, so I hadn't searched out an answer to it.

If I notice a sync issue in the future, how should I go about notifying WCMH?

[Guy Smiley]

Conan last night looked perfect

[festivus]

For me, only on the network HD feeds. Local seems fine. I should have said that. I really notice it while watching the office and my name is earl. I've not measured the delay. I have no way of doing that.

[NBC4ENG]

How is the timing between video and audio? Are we OK? I haven't heard any complaints. Let me know. Thanks.

[festivus]

Haven't noticed any out of sync broadcasts lately. NFL game on Sunday night was great.