Pre-flight checks for lip-sync inputs using ffmpeg and a local file validator

A tutorial describes building a small local script that verifies video and audio files before uploading them to Wan-family lip-sync tools. Public tool pages reportedly cap video at about 500 MB in MP4 or MOV format and audio at about 10 MB, and the author treats these limits as editable constants to update when the page changes. The script exits with a non-zero code on failure, so it can run in a folder action or CI step, and includes a self-test that writes synthetic files. The author notes that size checks cannot confirm mouth visibility or speech quality, so ffprobe should be used to inspect duration, resolution and track layout. Suggested fixes include re-encoding oversized video, exporting speech-only audio, remuxing wrong extensions, and trimming silence or stereo beds.