Acceptable Audio Latency and AV Sync Error

What is the “Best” Output Audio Latency?

Output audio latency measurements for consumer electronics, besides music creation and live performance technology, are relevant for audio/video synchronization (AV sync) in almost all cases. Even audio latency issues with Bluetooth headsets are most prominent when paired with a video output on a smartphone, tablet, or PC.

For this reason, the “best” output audio latency for any given device is the audio latency that will most closely match the video latency of the display it will be used alongside. Said differently, a system’s total AV sync error should be as close to zero as possible.

AV sync issues are more perceptible when audio leads video than when video leads audio.1 It is likely for this reason that an HDMI device with audio latency that is less than video latency by more than 20ms is forbidden by the HDMI Specification, since the required correction of this audio/video latency difference would “mean that an upstream device would have to delay the video (compared to the audio) which is cumbersome or impossible”.2 For these reasons, a lower audio latency is worse than a higher audio latency when video latency is high.

What is an Acceptable AV Sync Error?

Esports

Humans can react to auditory stimulus faster than visual stimulus,3 so audio latency should be as close to zero as possible without causing a notable amount of AV sync error. It is assumed that a display used for esports will have a low video latency, much less than 20ms, so simply using an audio device that has the lowest latency possible is preferred. This way, when paired with a low-latency display, AV sync error will not be a significant issue because both devices will have low latency.

Author’s note: I have measured latency of the BenQ ZOWIE gaming monitor to find a 1ms video latency and a 1ms audio latency. With this as a key reference point, I believe that it is reasonable that esports setups should have no more than 4ms of total audio or video latency.

General Use

While a significant amount of research has been performed to assess what AV sync error is acceptable to humans, it cannot be expected that all media and game content will have perfectly synchronized audio and video. For example, a television show or movie may have some scenes that have poor audio/video synchronization due to production quality limitations. Or a video game’s sound effect playback might be slightly delayed due to processing and lead-in time. When these existing AV sync errors are added to a AV sync error in the user’s setup, the combined error may exceed a threshold that can be noticeable to the user. For these reasons, a AV sync error as close to zero as possible is recommended.

Common Scenarios

The following list describes common consumer electronics setups and the challenges of audio/video synchronization that arise.

  1. A device where both audio and video output are handled by this same device, such as a TV.
    • Audio/video synchronization may be affected by different operation modes, such as a TV’s game mode. For example, the Sony X800H TV, which has approximately 4ms of video latency in game mode, has 96ms of audio latency in game mode when using speaker output.

Last updated on March 6th, 2023.

  1. ITU-R BT.1359-1, Figure 2
  2. HDMI Specification 2.0, Section 10.6.1.1 “EDID Latency Info – Devices without HDMI output”
  3. Comparison between Auditory and Visual Simple Reaction Times, Section 3 “Results”