Fix pixelated video with FFmpeg: the commands I actually use

The basic recipe

Deblock first, then denoise, then scale, then sharpen. Here is a good starting command for a blocky 480p or 720p clip:

ffmpeg -i input.mp4 -vf "deblock=filter=strong:block=8,hqdn3d=4:3:6:4.5,scale=1920:-2:flags=lanczos,cas=0.5" -c:v libx264 -crf 17 -preset slow -c:a copy output.mp4

deblock smooths block edges. hqdn3d is a fast 3D denoiser: the four numbers control spatial and temporal luma and chroma strength. scale with Lanczos enlarges the picture to 1920 wide and keeps the aspect ratio with -2. cas is contrast adaptive sharpening. CRF 17 is near visually lossless; raise it to 20 for smaller files.

Choosing strength

For mild noise, hqdn3d=2:1.5:3:3 is enough. For severely damaged video, increase to 5:4:8:6, but expect a softer picture. Lower sharpen values, such as cas=0.3, for already sharp footage.

If you enlarge by more than 2x, add a second light denoise pass after scaling, or use an AI upscaler for texture. nlmeans is a stronger but much slower denoiser worth trying on short clips.

Repairing a damaged file

First try a remux that ignores errors: ffmpeg -err_detect ignore_err -i broken.mp4 -c copy fixed.mp4. If that fails, re-encode with the same flag and drop the audio if it breaks: ffmpeg -err_detect ignore_err -i broken.mp4 -c:v libx264 -crf 18 -an fixed.mp4. A MP4 file with no moov atom cannot be repaired this way, because the index is missing.

Use the command, step by step

1. Install FFmpegUse your package manager or download a build from ffmpeg.org.
2. Probe the sourceRun ffprobe -hide_banner input.mp4 to see resolution, bitrate and codecs.
3. Run the recipe on a short clipAdd -t 10 to test only the first 10 seconds and tune values.
4. Encode the full fileRemove -t, keep CRF 17 to 20 and preset slow.
5. ComparePlay the output next to the input at 100 percent zoom.