3137.mp4

Use file 3137.mp4 to confirm it is actually an MP4 and not a renamed archive or polyglot file.

Briefly state what the goal was (e.g., "Find the hidden flag within the video file"). 3137.mp4

A quick summary of the trick (e.g., "The flag was hidden in the LSB of the audio channel"). Use file 3137

net/threads/pishem-ctf-writeup-pravil-no-zachem-eto-nuzhno-i-kak-pomogayet-razvitiyu.92117/">Codeby ? 3137)" -vframes 1 out.png .

If you found something in a single frame, explain how you extracted it using ffmpeg -i 3137.mp4 -vf "select=eq(n\,3137)" -vframes 1 out.png .