video-edit

Edits videos locally with ffmpeg commands for trimming, resizing, compressing, and converting.

Updated Jul 16, 2026
One-click install
npx skills add https://github.com/X-manist/Cohmira --skill video-edit-x-manist
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: video-edit
Source: https://github.com/X-manist/Cohmira/tree/main/src/builtin-plugins/openmontage/.agents/skills/video-edit
Command: npx skills add https://github.com/X-manist/Cohmira --skill video-edit-x-manist

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill requires ffmpeg, and includes references (resource) components.

What problem does it solve? Editing videos for social platforms usually requires heavy GUI software or memorizing complex ffmpeg flags. This Skill provides ready-to-run ffmpeg and ffprobe commands for the most common video editing operations, so you can trim, resize, compress, and convert videos directly from the command line. ## Core Features & Use Cases - Trim and Concatenate: Cut segments with stream copy for speed, or join multiple clips using the concat demuxer. - Platform Resizing: Built-in scale-and-pad presets for TikTok (1080x1920), YouTube (1920x1080), Instagram (1080x1350), and square formats. - Audio Operations: Extract audio to MP3/WAV/AAC, replace audio tracks, or mix original audio with new music. - Compression and Conversion: CRF-based compression, target file size calculation, and high-quality two-pass GIF conversion. - Use Case: You recorded a horizontal product demo and need a vertical TikTok version with a logo watermark. Use the resize preset with the pad filter, then apply the overlay command to place your logo in the corner. ## Quick Start Ask the AI to trim the first 30 seconds of demo.mp4 and resize it to 1080x1920 for TikTok using this video editing skill.

Frequently Asked Questions about video-edit

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I trim a video with ffmpeg without re-encoding?

Use ffmpeg with -ss and -to before the input file plus -c copy to cut segments via stream copy. This is very fast but cuts only on keyframes; for frame-accurate trims, re-encode with -c:v libx264 instead.

How to resize a video for TikTok using ffmpeg?

Apply the filter scale=1080:1920:force_original_aspect_ratio=decrease followed by pad=1080:1920:(ow-iw)/2:(oh-ih)/2:black. This fits the video inside vertical dimensions and adds centered black bars to reach exact TikTok resolution.

Does ffmpeg speed change work beyond 2x or below 0.5x?

The atempo audio filter only supports values between 0.5 and 2.0. For factors outside that range, chain multiple atempo filters such as atempo=2.0,atempo=2.0 for 4x speed, while adjusting video with setpts.

Why is my ffmpeg concat output corrupted or out of sync?

Concat with -c copy requires all input clips to share the same codec, resolution, and frame rate. When clips differ, re-encode during concatenation with -c:v libx264 -c:a aac to normalize the streams.

How do I compress a video to a specific file size with ffmpeg?

Calculate the target video bitrate as (target_MB * 8 * 1024) / duration_seconds minus the audio bitrate, then encode with -b:v, -maxrate, and -bufsize. For simpler quality-based compression, use -crf 23 with a medium preset.