Light blur
job_dc03006e09cd49eaRadius then power. Power is how many passes.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -vf "boxblur=4:1" -t 5 out.mp4video filter
The FFmpeg boxblur filter
Applies a fast box blur, commonly used to obscure a region.
3 of 3 variants measured Measured 2026-08-20
The part that catches people
boxblur blurs the whole frame. Blurring only a region means cropping the region out, blurring it, and overlaying it back, which is a three-filter chain rather than one argument.
Measured, not described
Every row below is a real job. The same 1280x720 five-second H.264 source went through each variant, so the numbers are comparable to each other and to every other filter page on this site. Encode time is the FFmpeg step on its own, separated from the download and the upload.
| Variant | Encode | Output | Cost |
|---|---|---|---|
| Light blur | 1078 ms | 352.1 KB · 1280x720 | $0.0025 |
| Heavy blur | 1216 ms | 301.6 KB · 1280x720 | $0.0027 |
| Region blur | 1061 ms | 516.1 KB · 1280x720 | $0.0025 |
The fastest variant here is not the smallest. Region blur finished the encode in 1061 ms, while Heavy blur produced the smallest file at 301.6 KB. Which one matters depends on whether you are paying for compute or for storage.
The exact commands
Heavy blur
job_dc41a4be241f4c95The obscure-a-face strength.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -vf "boxblur=20:2" -t 5 out.mp4Region blur
job_b99f694ef9834301The real pattern: split, crop, blur, overlay back.
ffmpeg -i https://cdn.rendobar.com/assets/examples/sample.mp4 -filter_complex "split[a][b];[a]crop=200:200:40:40,boxblur=20:2[bl];[b][bl]overlay=40:40" -t 5 out.mp4How these numbers were produced
Each variant was submitted to the Rendobar API as an ffmpeg job against the same public source file, and the response was recorded verbatim. Encode time is the API's own per-step timing for the FFmpeg step. Output size is the byte count of the file the job produced. Cost is what the job was actually billed.
Nothing here was estimated, and the whole set is re-runnable, so if a figure looks wrong it can be checked rather than argued about. The 72 variants behind this filter reference cost $0.193082 in total to measure.
Frequently asked questions
What does the FFmpeg boxblur filter do?
Applies a fast box blur, commonly used to obscure a region.
What is the most common mistake with boxblur?
boxblur blurs the whole frame. Blurring only a region means cropping the region out, blurring it, and overlaying it back, which is a three-filter chain rather than one argument.
How long does boxblur take to run?
On a 1280x720 five-second H.264 source, the fastest variant on this page (Region blur) spent 1061 ms inside FFmpeg. That figure is the encode step alone, measured separately from the download and the upload, so it is the filter's own cost rather than the round trip.
Do I need FFmpeg installed to use boxblur?
Not with Rendobar. Every command on this page ran through the Rendobar API against a URL, with no local FFmpeg install and no server. The job id next to each row is the real job that produced the numbers.
Other filters, measured the same way
scale Resizes video to a target width and height, with optional aspect-preserving arithmetic. crop Cuts a rectangle out of each frame, positioned from the top-left corner. fps Resamples video to a constant frame rate by duplicating or dropping frames. transpose Rotates video by 90 degree steps, optionally flipping as it goes. pad Adds bars around the frame to reach a target size without cropping the picture.
Run boxblur without installing FFmpeg
Every command on this page ran through the API against a URL. No binary, no server.