video-keyframe-extraction

name	video-keyframe-extraction
description	Use this skill to extract keyframes (I-frames) from an MP4 video file using ffmpeg. This produces numbered PNG files in a specified output directory.

How to extract keyframes from a video

Use ffmpeg to extract only I-frames (keyframes) from the video:

ffmpeg -i /root/super-mario.mp4 -vf "select=eq(pict_type\,I)" -vsync vfp /root/keyframes_%03d.png -y

This will produce files like /root/keyframes_001.png, /root/keyframes_002.png, etc.

Verifying extraction

After extraction, list the files to confirm how many keyframes were produced:

ls -1 /root/keyframes_*.png | sort

Count them:

ls -1 /root/keyframes_*.png | wc -l

Important notes

• The output format keyframes_%03d.png is zero-padded to 3 digits, starting from 001.
• ffmpeg numbers sequentially starting at 1.
• All keyframes are in timeline order by default.
• If the number of keyframes seems wrong, you can also try extracting at a fixed interval (e.g., 1 fps) using -vf fps=1 instead, but I-frame extraction is the standard approach for "key frames."
• Use ffprobe to check total number of I-frames beforehand if needed:

ffprobe -select_streams v -show_frames -show_entries frame=pict_type /root/super-mario.mp4 2>/dev/null | grep "pict_type=I" | wc -l