diff --git a/doc/demo.gif b/doc/demo.gif
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Binary files a/doc/demo.gif and b/doc/demo.gif differ
diff --git a/doc/gif-gen.md b/doc/gif-gen.md
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+++ b/doc/gif-gen.md
@@ -0,0 +1,9 @@
+# Generate the gif from video
+
+``` bash
+$ ffmpeg -v
+ffmpeg version 3.3 Copyright (c) 2000-2017 the FFmpeg developers
+...
+
+$ ffmpeg -i input.mov -vf  fps=15,scale=1920:-1:flags=lanczos output.gif
+```