AgentSkillsCN

ffmpeg-keyframe-extraction

使用 FFmpeg 命令行工具，从视频文件中提取关键帧（I 帧）。当用户需要从 MP4、MKV、AVI 等各类视频格式中提取关键帧、缩略图或重要画面，以进行分析、预览或后续处理时，可运用此技能。

SKILL.md
--- frontmatter
name: ffmpeg-keyframe-extraction
description: Extract key frames (I-frames) from video files using FFmpeg command line tool. Use this skill when the user needs to pull out keyframes, thumbnails, or important frames from MP4, MKV, AVI, or other video formats for analysis, previews, or processing.
license: Complete terms in LICENSE.txt

FFmpeg Keyframe Extraction

Extract key frames (I-frames) from video files using FFmpeg CLI.

Prerequisites

  • •FFmpeg installed and available in PATH
  • •Input video file (MP4, MKV, AVI, MOV, etc.)

Methods

Method 1: Select Filter (More Control)

bash
ffmpeg -i <input_video> -vf "select='eq(pict_type,I)'" -vsync vfr <output_pattern>
Method 2: Skip Frame (Faster)

ffmpeg -skip_frame nokey -i <input_video> -vsync vfr <output_pattern>
Key Options
Option	Description
-i <file>	Input video file
-vf "select='eq(pict_type,I)'"	Filter selecting only I-frames
-skip_frame nokey	Skip decoding non-keyframes (performance)
-vsync vfr	Variable frame rate, prevents duplicates
-q:v <n>	Quality (1-31, lower = better, for JPEG)
-frame_pts 1	Use presentation timestamp in filename
Output Patterns
frame_%03d.png - PNG sequence (frame_001.png, frame_002.png...)
frame_%03d.jpg - JPEG sequence
frame_%d.bmp - BMP sequence
Examples
Basic PNG extraction:

ffmpeg -i video.mp4 -vf "select='eq(pict_type,I)'" -vsync vfr keyframe_%03d.png High-quality JPEG:

code


ffmpeg -i video.mp4 -skip_frame nokey -vsync vfr -q:v 2 keyframe_%03d.jpg
With timestamps:


code


ffmpeg -i video.mp4 -vf "select='eq(pict_type,I)'" -vsync vfr -frame_pts 1 keyframe_%d.png


code

To specific directory:




ffmpeg -i video.mp4 -vf "select='eq(pict_type,I)'" -vsync vfr ./output/keyframe_%03d.png


code

## Notes
Method 2 (-skip_frame nokey) is faster as it skips decoding non-keyframes
Method 1 offers more filtering flexibility (can combine with other filters)
Keyframe frequency depends on video encoding settings
Use -vsync vfr to avoid duplicate frames in output