YouTube Audio Sync Fix Autor: Supreme Lobster

A small Manifest V3 Firefox extension that applies a targeted workaround for
audio/video drift in YouTube players.


When a ready YouTube video is playing, the extension records an eligible
Space press. If Space remains held for at least 400 ms, releasing it:

1. lets YouTube finish handling the key release;
2. seeks the video 0.10 seconds backward; and
3. returns to the original timestamp as soon as the first seek completes.

Firefox normally emits a seeked event after the backward seek. If it does not,
the extension restores the original timestamp after a 100 ms fallback timeout.
The two real seeks force Firefox's media pipeline to resynchronize audio and
video while leaving playback at effectively the same position.

The extension deliberately does nothing when:

• Space is tapped for less than 400 ms;
• there is no playing, ready video;
• the key press is a repeat or uses Control, Alt, or Meta;
• focus is in an input, text area, editable element, or textbox; or
• the window loses focus before Space is released.

If the original video is removed before resynchronization starts, the extension
looks for another playing video in the same YouTube document. It safely stops a
pending seek when its video is no longer playable or connected. There is no
toolbar UI, background script, settings page, or automatic drift detection.


The content script is only injected into:

• https://*.youtube.com/*
• https://*.youtube-nocookie.com/*

The manifest sets all_frames: true, so the extension also works inside
YouTube player frames embedded on other websites. Only the matching YouTube
frame receives the content script; the extension does not receive access to
the surrounding website.