Ffmpeg keyframes

Skill cxcscmu/SkillLearnBench/skills/b1-one-shot-claude-sonnet-4-6/video-object-counting/ffmpeg-keyframes

[COLM'26] SkillLearnBench is the first benchmark for evaluating continual learning methods that automatically generate agent skills.

Install

npx -y skills add cxcscmu/SkillLearnBench --skill ffmpeg-keyframes

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What its author says it does

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Extract I-frame keyframes from video files using FFmpeg command line, saving them as numbered PNG images.

SKILL.md

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FFmpeg Keyframe Extraction

Installation

sudo apt-get install ffmpeg
# or: conda install -c conda-forge ffmpeg

Extract All I-Frame Keyframes

ffmpeg -i input.mp4 -vf "select=eq(pict_type\,I)" -vsync vfr /output/keyframes_%03d.png

select=eq(pict_type\,I) — selects only I-frames (keyframes)
-vsync vfr — variable frame rate to avoid duplicate frames
%03d — zero-padded 3-digit frame numbering (001, 002, ...)

Extract Frames at Fixed Interval

ffmpeg -i input.mp4 -vf "fps=1" /output/frame_%03d.png   # 1 frame per second
ffmpeg -i input.mp4 -vf "fps=0.5" /output/frame_%03d.png # 1 frame every 2 seconds

Get Video Info

ffprobe -v quiet -print_format json -show_streams input.mp4

Python Wrapper

import subprocess, glob, os

def extract_keyframes(video_path, output_dir, pattern="keyframes_%03d.png"):
    os.makedirs(output_dir, exist_ok=True)
    output_pattern = os.path.join(output_dir, pattern)
    cmd = [
        "ffmpeg", "-i", video_path,
        "-vf", "select=eq(pict_type\\,I)",
        "-vsync", "vfr",
        output_pattern, "-y"
    ]
    subprocess.run(cmd, check=True, capture_output=True)
    frames = sorted(glob.glob(os.path.join(output_dir, "keyframes_*.png")))
    return frames

Notes

I-frames are self-contained frames, ideal as keyframes for analysis
Output numbering starts at 1 by default (001, 002, ...)
Use -y to overwrite existing files without prompting