LG OLED C1/C2 eARC Lip Sync: Fix Audio Delay Without Guessing

Quick Answer

Fix eARC lip sync by first determining whether sound arrives before or after the picture. Test the same clip through TV speakers, then through the eARC soundbar/receiver using PCM, and finally with the desired Dolby format. Disable unnecessary video processing, use only one device's delay control, and compare internal apps with an HDMI source.

Most delay controls can postpone audio; they cannot make already-late audio arrive earlier. If sound is late, reduce processing or change the signal route—for example, connect the player directly to the receiver—rather than adding more delay. Keep a written baseline because TV, source and audio device may each expose separate sync controls.

Lip-Sync Symptoms

Choose a scene with a clear consonant, hand clap or hard visual impact:

Lips move and the voice follows later: audio is late.

Sound occurs first and lips move afterward: audio is early.

Internal apps are synchronized, but one HDMI source is not.

TV speakers align, while eARC audio is delayed.

PCM aligns, but Dolby Digital Plus or Atmos is late.

Movies are wrong but Game Optimizer is correct, or vice versa.

Delay changes after enabling motion interpolation.

Audio disappears or the receiver loses format lock. That is a dropout, not a steady sync offset.

Sync gradually drifts over a long program. That differs from one constant offset and may involve the app/source clock.

Do not use a dubbed film, Bluetooth headphones or a social-media clip whose source synchronization is unknown. A purpose-made AV sync pattern or locally stored known-good clip is better.

Causes: Where Delay Accumulates

Television video processing

Motion interpolation, noise reduction, scaling and some HDR processing can delay the picture. HDMI lip-sync signaling can communicate latency, but multi-vendor devices do not always compensate identically. Game Optimizer reduces video processing, which is why a sync problem may change by picture mode.

Audio decoding

PCM arrives already decoded; Dolby Digital Plus, Atmos or another bitstream must be decoded by the TV or receiver. Codec changes can alter delay. C1/C2 codec support differs from later LG generations, so do not assume a modern-model pass-through guide applies.

eARC topology

A source connected to the TV sends video to the panel and audio back over eARC. A source connected to the receiver sends audio directly while video travels onward. These routes distribute processing differently. Neither is universally best, particularly when an older receiver cannot pass 4K120/VRR.

Multiple delay controls

Apple TV, console, LG AV Sync, soundbar and receiver can each add offset. Two positive delays stack. Factory reset is rarely needed; first return all documented user delay controls to neutral and choose one adjustment point.

App or source error

One streaming title, broadcast or app can be out of sync before reaching the television. If TV speakers and external audio share the same offset at the same timestamp, the source is likely.

Step-by-Step Lip-Sync Diagnosis

1. Establish a known clip

Use a local AV sync test or a scene with visible impact and unambiguous sound. Replay the same seconds. Phone slow-motion can help compare timing, but its microphone/camera pipeline also has latency; use it for relative before/after results, not laboratory milliseconds.

Record the active source, app, LG picture mode, sound output and receiver format.

2. Test TV speakers

Select TV Speakers and replay. If the offset remains, eARC is not the first cause. Compare another app and internal versus HDMI playback. Turn off motion interpolation temporarily. If changing picture processing alters synchronization, keep the preferred picture mode and account for its latency later.

3. Build a minimal eARC system

Connect only the soundbar/receiver to the LG port labeled eARC and enable the supported eARC/Simplink path. Disconnect other HDMI devices temporarily to remove CEC switching. Start with an internal app so video never traverses an external HDMI source.

If internal TV audio is synchronized over eARC, add the external source next. The difference identifies the source path.

4. Compare PCM and bitstream

Send stereo PCM first, then a supported multichannel PCM configuration, Dolby Digital Plus and the required Atmos path. Note the receiver's actual display. If only one codec is late, decide whether the source can decode to PCM or whether direct-to-receiver routing is more appropriate.

Do not mistake unsupported DTS handling on C1/C2 for a delay. Missing sound requires a compatible decode route.

5. Reset user delay controls

Set LG AV Sync adjustment, receiver lip sync and source delay to their neutral/default positions. Photograph original values first. Disable bypass only when its description is understood. Use one device for final correction so the total remains traceable.

6. Determine direction

If audio is early, add audio delay at the receiver or LG until the impact aligns. If audio is late, a positive delay makes it worse. Reduce video processing, select Pass Through/PCM as appropriate, or change source routing.

Some devices offer negative adjustment conceptually by delaying video or using an auto-lip-sync feature, but availability varies. Do not enter factory/service menus to obtain a wider range.

7. Compare routing

Connect a streamer or disc player directly to the receiver. If sync improves, TV return-path or pass-through processing contributed. For PS5/Xbox/PC 4K120 VRR, the receiver may block video features; direct-to-TV plus eARC may still be necessary. In that case, prefer a compatible audio format and minimal processing.

8. Reintroduce CEC and sources

Reconnect devices one at a time, test wake/input changes and ensure the chosen delay survives. If another device changes audio destination or format, inspect its HDMI-CEC controls. Sync and dropouts after standby can share a handshake cause but require separate evidence.

C1/C2 and Mode Caveats

C1/G1 use the 2021 webOS audio-menu layout; C2/G2 use the 2022 structure. AV Sync Adjustment, Bypass, eARC Support, Auto and Pass Through may be named or positioned differently. Follow on-screen descriptions for the installed firmware.

Picture modes also matter. Cinema with TruMotion can have more video latency than Game Optimizer. Do not use a single delay value for both if the equipment cannot automatically track reported latency. A console game and a 24p film can require different routing.

Bluetooth adds its own buffering and is not a valid baseline for eARC. Optical audio is useful as a comparison but has different codec/bandwidth support.

Safe Fixes and Cautions

Use the fewest active processors and one documented delay control. Update TV, source and audio device with stable public firmware, then repeat the known clip. Keep cable changes focused: a bad link more commonly causes dropouts than a constant offset, but a short known-good cable is useful when eARC loses lock.

Do not change service-menu values, panel settings, TPC/GSR or white balance. None controls audio timing. Do not factory-reset the TV before minimal-topology tests; it erases unrelated setup.

Contact LG when supported internal apps are consistently out of sync over multiple known-good eARC devices after updates. Contact the audio manufacturer when TV speakers align and only that product remains late. Provide topology, format, firmware and measured direction.

HDMI Licensing Administrator — eARC and lip-sync capabilities

LG — Troubleshooting no audio from an LG TV

Dolby — Dolby Atmos home theater setup

Apple — Wireless Audio Sync on Apple TV

Xbox — Choosing speaker audio output

Reddit — LG OLED owner discussions of eARC lip sync