Why does my TV sound keep going out of sync?

Audio sync issues, also known as lip sync errors, refer to a lack of synchronization between the audio and video portions of a TV signal. This causes the sound to be out of alignment with the visuals displayed on the screen. For example, you may notice a delay where the audio lags behind the video, so the mouths of people on screen do not match up with the words being spoken. Lip sync problems are a common technical frustration that can detract from the viewing experience. They can be caused by various faults in the transmission, processing, or output of the audio and video portions of the signal. Troubleshooting audio sync issues involves diagnosing the underlying cause and applying the appropriate solution to realign the timing of the audio feed with the video. With some detective work and the right fixes, it is often possible to resolve lip sync problems on a TV.

What Causes Audio Sync Issues

There are several technical reasons that can cause audio to go out of sync with video on a TV. The main causes include:

Audio Encoding Latency: Digital audio signals take time to encode and decode, which can introduce small delays. Audio codecs like Dolby Digital can have up to 100ms of latency (https://www.tcl.com/global/en/blog/tips/how-to-fix-your-tcl-tv-audio-and-video-out-of-sync-error).

Video Processing Delay: Complex video processing inside modern TVs, like upscaling and motion smoothing, can delay the video signal slightly. This delay between video and audio getting displayed can cause sync issues.

Mismatched Output Times: If the audio output has a different delay than the video output inside the TV, it can cause sync drift over time. Audio may lag behind progressively as the content plays.

Connection Bandwidth Issues: Insufficient HDMI bandwidth connecting source devices to the TV can also introduce audio delays or lipsync issues.

Audio Encoding Latency

Audio encoding latency is one of the most common causes of audio going out of sync with video. Encoding refers to the process of compressing the audio into a digital format to be stored or transmitted. This compression introduces a slight delay as the encoder samples, processes, and packets the audio data (Source). The more complex the encoding algorithm, the longer it takes to encode the audio and the higher the latency.

For example, advanced audio codecs like Dolby Digital can have over 100ms of latency due to the encoding process. Simpler codecs like PCM have much lower inherent latency. So using Dolby Digital audio with video can require compensation to avoid lag (Source). The encoding latency may be consistent, but over time can still cause sync issues if not properly aligned with the video.

Video Processing Delay

Video signals go through extensive processing within modern TVs before being displayed. This processing introduces delay as the TV analyzes and optimizes the video feed. According to the Sony support article, “The audio and video are out of sync or there is a delay” [1], video processing can add 100-500 ms of delay. More advanced processing like upscaling SD video to HD, motion smoothing, and noise reduction tend to cause more lag. Essentially, the more a TV has to process and modify the video before displaying it, the more delay that is introduced. This extra video delay then causes A/V sync issues since the audio does not undergo the same processing path and latency.

Newer TV models with more advanced video processing tend to have more delay. As explained on Reddit [2], “You’ve getting a delay because of the processing of the video signal. As a rule of thumb, for each device you add to the chain you’re adding delay.” So all the optimization happening within the TV takes time and slows down video output compared to the audio.

Mismatched Output Times

One common cause of audio sync issues is mismatched output times between the audio and video signals. This can occur when the audio and video are processed through different pathways before being output to the TV speakers or external audio system.

For example, many TVs process the video through onboard circuitry that can introduce a slight delay before sending it to the screen. Meanwhile, the audio may bypass this and get sent directly to the speakers or audio output. The result is the audio arrives slightly ahead of the video, causing lip sync problems.

Even small mismatches measured in milliseconds can be perceptible. According to Sony [1], audio delays greater than 90ms compared to video can lead to noticeable sync issues.

The problem may be worsened if connecting to an external speaker system using cables or wireless transmission. These connections can introduce variable delay as well.

To resolve mismatched outputs, TVs provide audio delay calibration settings, often accessible through the audio menu. Increasing the audio delay gradually until the sync issue disappears can align the timing.

Connection Bandwidth Issues

One common cause of audio sync problems is insufficient bandwidth on the connection between your TV and audio device. Most modern TVs and soundbars use a digital audio connection like HDMI ARC/eARC, optical, or Bluetooth. All of these require a certain minimum bandwidth to transmit the full quality audio without delay or skipping.

For example, a typical 5.1 surround sound audio track requires up to 6 Mbps of bandwidth. If your internet connection bandwidth drops below this, such as during periods of network congestion, the TV may temporarily reduce the audio quality or delay the audio to prevent skipping. This introduces a noticeable lag between video and audio.

According to Samsung Support, enabling the “Low Bandwidth Audio Sync” setting in your TV’s menu can help minimize audio delays during periods of low network bandwidth by changing the audio codec [1]. However, reducing audio quality is not an ideal solution. The best fix is increasing your network bandwidth to meet the minimum requirements.

Upgrading your internet plan, resetting your modem/router, reducing interference, or using a wired Ethernet connection instead of WiFi are some ways to boost your available bandwidth. If sync issues only occur during peak usage times, limiting other network activity can also help.

Detecting Sync Problems

There are a few telltale signs that can help you identify if audio and video are out of sync on your TV:

https://www.wikihow.com/Fix-Sound-Delay-on-TV

– Mouth movement won’t match the words you hear. You may notice a character finishing their sentence but their lips keep moving. Or you may hear words before a character’s mouth starts moving.

– There’s an echo effect. The audio may be slightly behind the video, so you hear a word just after the character’s lips say it.

– Actions and sound effects don’t line up. For example, you may see a door slam but hear the sound fractionally later.

– Music and vocals fall out of sync. Songs may sound off, with singers’ mouths moving out of time with the lyrics.

Pay close attention if video seems fine but the audio is delayed. The delay may only be fractional but you’ll likely notice it, especially with speech. Test different shows and movies to see if the sync issues persist.

Troubleshooting Steps

There are several steps you can take to diagnose the root cause of audio sync issues on your TV:

• First, check all of your connections and cables to ensure they are securely plugged in. Loose HDMI or audio cables can cause sync problems. Refer to your TV manual if needed. [1]
• Try connecting your devices using different ports or cables. For example, connect your Blu-ray player directly to the TV instead of through a receiver. This can identify if the issue is with a faulty cable.
• Reset or power cycle your audio system and TV. Unplug them from power for 2-3 minutes before plugging back in. [2]
• Check for firmware updates from your TV and audio system manufacturers. Install any available updates which may resolve AV sync bugs.
• Adjust audio delay/sync settings on your TV, AV receiver, or streaming device. There may be a specific setting to resync audio.
• Try different media sources and content. If the sync issue only occurs with certain apps or devices, it points to a source problem.

Following these steps methodically can help narrow down where the sync issue is stemming from. If the problem persists, contact the device manufacturer for further troubleshooting.

Resolving the Issue

There are various solutions for resolving audio sync issues depending on the underlying cause.

Audio Encoding Latency

If the cause is audio encoding latency, try changing the audio settings on your TV or streaming device to a different format like PCM or Dolby Digital that has less processing lag. You can also look for an “audio sync” or “AV sync” setting to add a slight delay to the video to match the audio (Sony).

Video Processing Delay

For video processing delay, turn off any video post-processing effects or modes on your TV like motion smoothing, noise reduction, or sharpening which can slow down the video. Disable anysoap opera effect settings. Check for a ‘game mode’ which optimizes for faster response time (WikiHow).

Mismatched Output Times

If audio and video are being output at different times, try connecting audio directly to the TV rather than passing it through an external receiver or soundbar first. If using cables, upgrade to higher quality HDMI or optical cables which can improve sync issues.

Connection Bandwidth Issues

For bandwidth-related problems, reduce the resolution being output by the source to ease the bandwidth burden. Or try swapping cables and connections to isolate any defective cables unable to properly handle the full signal.

Adjusting these settings can often resolve sync problems and realign audio and video output.

Preventing Future Problems

There are some steps you can take to help prevent audio sync issues from happening again in the future:

Upgrade to high-speed HDMI cables – Using the latest HDMI cables that support 18Gbps bandwidth or higher can help prevent sync delays caused by insufficient bandwidth (source: https://www.wikihow.com/Fix-Sound-Delay-on-TV).

Keep your devices updated – Install the latest firmware updates for your TV, audio system, streaming devices, etc. Updates often include improvements to timing and sync (source: https://softwarekeep.com/help-center/how-to-fix-audio-and-video-out-of-sync-in-windows-10).

Avoid using too many devices – Connecting multiple devices like soundbars, streamers, receivers, etc. can introduce delay. Try to minimize the devices between your source and TV (source: https://www.wikihow.com/Fix-Sound-Delay-on-TV).

Adjust TV settings – Enable options like Auto Lipsync or A/V Sync to allow your TV to automatically adjust timing. Turn off extra video processing like motion smoothing which can delay video (source: https://softwarekeep.com/help-center/how-to-fix-audio-and-video-out-of-sync-in-windows-10).

Change audio output – If using external speakers, try the TV’s internal speakers to isolate the issue. Switch digital outputs to PCM to remove encoding delay (source: https://www.wikihow.com/Fix-Sound-Delay-on-TV).