I have a short screen recording of an old video game (duration 1:38.72, 2468 frames, 25 fps, 320×200 px, 4 colours only, bgr24, CamStudio Lossless Codec, no sound, AVI).

The video contains an incorrect area (static, 16×16 px, top left corner at [136, 144]) in a range of frames (starting at 0:43.88 and ending at 1:38.44).

I'd like to replace that area in that range with correct data, everything losslessly.

I searched for "replace area in range of frames" on this server but didn't find anything.

Would you know how to do that with free software on Windows please? Maybe FFmpeg?

2 Answers 2


I don't know if FFmpeg supports the Camstudio Lossless Codec, but if it would. Then replacing the area with a PNG file (hence: adding a logo) could be a solution.

The explanation is done here at "Timing the overlay". https://superuser.com/questions/683643/how-to-add-my-logo-for-the-first-30-seconds-in-a-video-with-ffmpeg

In that example codec:a copy was already given (for audio). If you would take any lossless videocodec the result will be lossless.

  • I'm surprised the overlay filter processing does not take place at RGB or YUV444. Great catch.
    – Skinkie
    Commented May 4, 2021 at 10:07
  • Thanks for pointing me to overlays, Skinkie! I've checked Low power's answer at ffmpeg - how to apply filters without losing quality and overlays in FFmpeg documentation. The command that will do the magic is: ffmpeg -hide_banner -i input.avi -i patch.png -filter_complex "[0:v][1:v]overlay=136:144:enable=between(t\,43.88\,98.44):format=auto" -f yuv4mpegpipe -pix_fmt yuv444p output.y4m Commented May 5, 2021 at 6:44
  • OK, it's not exactly lossless because the color space conversion from bgr24 to yuv444 alters the colors slightly. But I still internally consider it lossless because no artifacts are introduced and the output still has exactly 4 colors. :-) Commented May 6, 2021 at 5:32

I would use Davinci Resolve to do this. It is free, runs on windows, and has great object removal tools.

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