A “lip sync problem” is when your brain finds a discrepancy between your TV’s audio and video. Your brain expects the sound of someone speaking to match their lip movements and it’s uncomfortable when they don’t– which has become more apparent with today’s large TVs.
Also, people vary in their awareness of lip sync; just as athletic ability varies among people, so does their sensitivity to lip sync problems. Some don’t see 15 ms errors (milliseconds, 1/1000 second), but once aware of them they see smaller errors. Before the fix that led to this post we had a 2 ms problem, which bothered us enough when we were watching carefully – a good movie, for example – that we needed to find a way to fix it..
Movies in theaters seldom had a lip sync problem because their audio came from the edge of the film strip. Early TVs didn’t because the entire box was under the manufacturer’s control, the smaller screen made it less obvious, and they could make it right. But today’s more complex technology has created a new common problem: lip sync, specifically audio-to-video synchronization. Enough about what it is, let’s see what we can do about it – if we just can’t ignore it. But first, a digression:
Discussing lip sync problems is surprisingly difficult. I found it far too easy to write the opposite of what was correct. Trying to address this, I write only of the order in which the audio and video from the TV reach the viewer.
It’s also difficult to tell which is behind, video or audio. When I have trouble doing it with speech I look for a single identifiable sound – explosion, bat strike, etc. – to be sure which is behind. And even then I rewind and watch several times.
The video is behind the audio
You hear someone say “hi” before you see their lips move – this is the most common lip sync problem. The usual reason is that your TV takes longer to process the video than the audio because the video is more complex. For instance, our 12 year old TV takes 112 ms to process the video but delays the audio by 100 ms, leaving the video 12 ms behind the audio.
If you’re a sports fan you may enjoy watching TV while listening to a radio station. Frequently you find the TV signal from the game has a long delay – 30 seconds or more – allowing removing events from the broadcast, or maybe to discourage you from doing what you are doing. Most find this very frustrating: you hear the announcer get excited and 30 seconds later you see the bat swing.
Two ways to fix it: (1) delay the audio; and, (2) process the video faster.
You can do either or both. You can delay the audio with an audio delay box (see below). For faster video processing, Lifewire points out that video processing takes time and you may be doing it twice – in both your TV and an audio-visual receiver or preamp. If so, you only need to do it in one place – using the fastest processor, I’d add – and you may not need to do all the processing that you are doing. The less video processing you do, the faster it will be.
The audio is behind the video
You see someone’s lips move before you hear them say “hi”. Too much audio delay – from your equipment, TV station, filmmaker, or a combination – causes this problem.
Two ways to fix it: (1) delay the video; and, (2) reduce the audio delay.
Delaying the video seems like delaying the audio, but it’s not. Delaying video is much more expensive because there is so much more video information. While doing the opposite of what Lifewire suggested above might delay the video a bit, reducing the audio delay may be easier.
You may be delaying the audio without knowing it.
- Your TV may have an audio delay. (Nick Johnson of Felston finds that all TV manufacturers except Samsung and Vizio delay the audio. Of course, this isn’t a problem unless they delay the audio until it is behind the video, but it certainly reduces your ability to correct lip sync errors.)
- Some external speaker systems and soundbars have built-in audio delay (Here are 20 pages discussing LG/Sonus lip sync problems. My conclusion from this multi-year discussion is that a built-in audio delay increases the likelihood of too much overall lip sync correction because it’s too easy for a company to assume they are making the only lip sync correction – and then they add up, creating this type of lip sync problem.)
- Many audio-visual receivers and preamps can delay the audio.
So before you conclude that the audio is behind the video, look at the manuals and settings for all of your gear – you may be able to fix or identify the problem.
If the video is still ahead of the audio and your TV delays the audio then you can use the audio before it gets to your TV. To do this you would use an “HDMI audio extractor” (see below). This will certainly reduce your lip sync problem and may solve it. If you find that the audio is now ahead of the video, reread and follow the section above. If it’s still behind then you will either have to live with it or replace whatever equipment is still delaying the audio.
Finally, Don Moser of Motron Electronics, points out that if the radio broadcast from a sporting event is delayed enough to place the audio behind the video broadcast you can fix this using a DVR. Pause and resume your DVR for long enough that the video is behind the audio and use an audio delay box to sync them.
Fixing Lip Sync Problems
So, to fix lip sync problems you may need one or two boxes and the wires to connect them: an audio delay box and an HDMI audio extractor box. This is where the wish to fix the problem stops for many, it just seems too complex and scary. It won’t be either if you go step by step. Install one box at a time, making sure everything works before and after each box is installed (labeling the wires helps). When I do something like this I frequently knock a wire loose – generally a speaker wire as the path to the back of our gear lies through a speaker. While I know neatness helps, I struggle to maintain it because there’s not much room and no one can see our wires. But I’m improving; the latest change is neater than previous changes – mostly because I added a spread-out 8-socket power block so only one power wire leaves that piece of furniture.
Audio Delay Boxes – Available in two types, analog and digital. Choose analog if your only available audio out is analog, if you want to sync TV and radio sports broadcasts, or you need to delay computer audio for better on-line conferences. Choose digital if your only available audio out is digital, you use surround sound, or your equipment requires doing so. I recommend both of these audio delay boxes; they are well made, have remotes, display the set delay, pass through the signal when turned off, and are well-supported by their makers.
Analog Audio Delay Box – The Motron RTS-200C is my choice for analog input and output. It is unique in that it can delay the audio up to 86 seconds – more than enough to sync sports broadcasts. This is the appropriate unit for video conferencing too, as most computer audio out is analog.
Digital Audio Delay Box – The Felston DD740 is the unit I chose because I needed digital delay due to our other equipment. It provides only digital input and output and it can delay the audio up to 680 ms (0.68 seconds). I am completely happy with it.
HDMI Audio Extractor Boxes – Even if you need one, perhaps you can still avoid using one. If you have a cable box, satellite box, or digital video recorder (DVR), it may have an audio out connection (many DVRs have one). Using an audio out connection before your TV does the same thing as using an extractor box – and saves you money. So, please look at your equipment first.
HDMI is the kind of cable (or wire) that caries the TV signal from your cable or satellite box to your TV. (The ends look like the picture below.) An HDMI audio extractor box goes between your cable or satellite box and your TV – where your old cable is – so you will need a second HDMI cable. To install it, remove the old HDMI cable from the TV and plug your new cable in the same socket. Plug the other end of the new cable in the “Out” socket of the audio extractor box. Plug the old cable (that used to be plugged into the TV) in the “In” socket of the audio extractor box. Now the audio extractor box is between the cable or satellite box and your TV. The TV signal passes through the box without any changes.
The “extractor” part is one or more audio out connectors, which can be digital and/or analog. The HDMI portion must be at least as good as your TV signal (HD, 4K, or 8K), but I haven’t seen one rated 8K yet. Some of these units are combined with an HDMI switch and remote. These are useful if you have more than one TV input with audio to extract and the switch adds little to the cost.
HDMI Analog Audio Extractor Box – There are more than a dozen different boxes available on Amazon, all of them cheaper than my preferred digital audio extractor. Most of them are also available elsewhere. You should choose one that has the type of analog audio connector that fits your needs. For example, 3.5 mm stereo for computers and RCA Right/Left for most TV speaker systems.
HDMI Digital Audio Extractor Box – While I haven’t tried it, I like the Tripp-Lite 4K HDMI Audio Extractor. I’ve used other Tripp-Lite gear and was happy with it. I particularly like that this unit has both optical and RCA digital outputs; while it also has 3.5mm stereo analog output, there are cheaper alternatives if analog is all you need.
Conclusion
We have found that our audio delay box adds to our TV enjoyment. Once we found the proper delay for our normal TV stations we’ve rarely had to adjust. We hear no difference in the audio itself from the delay box. For us, it is worth the hassle and expense to remove the source of such frequent irritation.
Residual Questions
It’s not my equipment causing it, how did I get a lip sync problem?
Equipment exists to put lip sync markers in both the video and audio streams – ensuring perfect lip sync – but it must be done by the video maker and no one is doing it! TV stations would have to purchase corresponding equipment to maintain the lip sync, but they don’t do so because there are no shows that contain the lip sync signals. This is an example of the classic chicken-or-egg problem; neither will purchase and use the new equipment until the other does.
Since equipment to solve the problem isn’t being used, we have to rely on people doing things properly – and, of course, they don’t always do so. If everything from a TV station has this problem, perhaps telling the station about it will lead to a fix. But there are so many firms creating video that there’s nothing an individual can do about them.
Why is it so expensive to delay a video signal?
Audio bandwidth is measured in megabits (millions of bits per second) while video signals are measured in gigabits (billions of bits per second). To delay a signal – audio or video – the information is placed in memory and recovered later. Video needs more than 1000 times the memory, increasing the cost of a delay box. Also, the TV signal needs faster hardware, further increasing the cost of video delay. In a brief search for a video delay unit, I found 20 second video delays for $3K (HD) and $8.7K (4K). A home TV needs about 200 ms video delay.
How did you determine your computer’s audio delay?
I already knew that the video was behind the audio, so I bought a DD740 audio delay box and placed it between our TiVo box and the preamp that controls the separate speakers. Using the TiVo’s audio out, I played the same program audio through the TV speakers and the separate speakers – the audio was garbled because of the two different delays. I changed the audio delay until they were perfectly in sync and it sounded like one speaker system.
Why did you drive your separate speakers with the TV’s audio out?
The objectives for the equipment change that generated this post were (1) fix the lip sync problem; and, (2) simplify. As we have a Roku attached to the TV, using the TV’s audio out was the simplest means of switching the Roku’s audio – as no other settings needed to be changed. I ran connections from both the TV’s digital audio out and the TiVo’s optical audio out to the DD740; the TV’s audio out needs a 12 ms delay and the TiVo needs a 112 ms delay. So only a program that needs < 100 ms delay would be a problem – which I don’t expect to find. While I suspect our TV provides an amplified digital audio out because it’s louder than the TiVo (theoretically reducing the audio quality), simplicity caused me to use the TV’s audio out.
How do I tell if my TV’s audio out is analog or digital?
Your TV’s manual probably says; but if not (or you can’t find the manual), look at both the number and color of the TV’s audio out connectors. They will generally be what are known as RCA connectors, physically the same as most other wires used for non-speaker connections. If they are RCA connectors, there will be two analog audio out sockets – but just one digital audio out socket. Analog audio is usually labeled and color-coded red for right and white for left; digital audio is usually black. More rarely: if the connector is a 1/4” or 1/8” hole, the connection is analog; and if it is a coaxial socket – usually screw-on – it’s digital. Finally, if there’s a rectangular hole with a plastic flap over it the connection is optical and is digital.
Why do you use the DD740 instead of the RTS-200?
I learned in the past that we need balanced connections from the preamp in our room to the amplifiers. As the RTS-200 connections are analog while everything is digital before our preamp, I couldn’t use an analog delay without giving up the balanced connections. These are commonly used in professional audio – concerts and recording studios. They operate at a higher voltage (so noise is smaller when compared to the signal) and use a connection that allows noise to be electronically removed from the signal – allowing their lengths to be much longer. They’re not necessarily more expensive, but not all equipment has the connectors.
What about the rest of your equipment?
The rest of our equipment is covered in another blog post, TV and Stereo Interests.
June 27, 2020