webm-reencode-for-chrome-seek
This skill contains shell command directives (!`command`) that may execute system commands. Review carefully before installing.
webm-reencode-for-chrome-seek
A reusable utility for fixing webm videos that fail to decode in Chrome when a URL fragment (e.g. #t=0.1) triggers a seek-on-load before the first keyframe.
When to use
Apply this skill when all of the following are true for a file:
- A
<video>element fails to play in Chrome/Chromium. video.error.code === 3with messagePipelineStatus::PIPELINE_ERROR_DECODE: video decode error!.- The same file plays fine in Safari.
- The same file plays in Chrome with no URL fragment, but fails with
#t=0.1(or any#t=...).
Root cause: VP9 can only begin decoding at a keyframe. If the file's first keyframe is not at t=0, a seek to 0.1s before playback lands mid-GOP and Chrome's pipeline errors out. Safari's decoder is more forgiving.
The magentaA11y repo appends #t=0.1 in src/components/content-display/markdown-content/elements/markdown-source/markdown-source.tsx so Safari preloads the first frame as a pseudo-poster. This skill preserves that behavior and fixes the video files instead.
Not iOS-specific. The bug surfaced on iOS VoiceOver videos because of how they were originally captured, but the fix applies to any webm with a late first keyframe. Run this skill on any new webm that shows the decode symptoms above.