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The audio protocols Airfoil uses to stream to devices feature inherent delays. As a result, remote playback of audio streamed with Airfoil will be slightly delayed, so it can be heard in sync from all devices. Read on for more details.
When starting your audio streaming with Airfoil, the initial transmission delay will vary based on the exact devices you're streaming to.
Airfoil will delay all playback to match the highest delay required.
Airfoil is not intended for use with local video playback. Because of the audio delays inherent in transmitting audio, remote audio will be heard out of sync with local video, resulting in a sub-optimal viewing experience. While we generally do not recommend doing so, it is possible to use Airfoil in conjunction with media player apps which offer a manual sync adjustment.
One such player is VLC. Using the sync adjustments available in VLC, you can offset audio playback from video playback, to workaround the delays noted above. With the right manual configuration, you may be able to sync remote audio with local video. Please note, however, that this usage is not supported.
Another option is IINA, a newer video player made for MacOS. Like VLC, it offers manual controls within the video settings overlay, as well as from the Audio menu in the menu bar.
Airfoil automatically works to keep any and all devices to which it's streaming in sync with one other. Most users should have no need to manually adjust the sync offset.
In rare cases, however, a device may have a separate delay which causes it to fall out of sync. If a speaker has an unexpected amount of additional latency, audio may not be heard in perfect sync. You can correct this using the controls in Airfoil's Advanced Speaker Options window.
The sliders in this window can be used to manually offset the sync between devices:
The controls in the Advanced Speaker Options window provide a constant latency adjustment, and are remembered between launches of Airfoil. With a bit of trial and error, you may be able to adjust settings to get perfect sync.
If a device has a fluctuating amount of latency, these sliders won't be able to correct things permanently. This can occur when there's an issue with the local network, interference from other sources, or an issue with the device itself. When these problems arise, it may be impossible to sync multiple outputs.