How to Create a Tilt-Shift Effect in FFmpeg

This article provides a straightforward guide on how to simulate a tilt-shift depth-of-field effect on Standard Dynamic Range (SDR) video using FFmpeg. You will learn how to use a combination of splitting, blurring, and mathematical blending filters to keep the center of your footage sharp while smoothly blurring the top and bottom edges to create a miniature toy-like perspective.

The Tilt-Shift FFmpeg Command

To achieve a tilt-shift effect, you must split your video into two paths: one that remains sharp and one that is heavily blurred. You then blend them back together using a linear gradient mask that targets the vertical Y-coordinates of the frame.

Run the following command in your terminal:

ffmpeg -i input.mp4 -filter_complex \
"[0:v]split[sharp][temp]; \
 [temp]boxblur=luma_radius=15:luma_power=3[blurred]; \
 [blurred][sharp]blend=all_expr='A*(abs(Y-H/2)/(H/2)) + B*(1-(abs(Y-H/2)/(H/2)))'[out]" \
 -map "[out]" -c:a copy output.mp4

How the Filter Chain Works

• split[sharp][temp]: This splits the input video stream into two identical streams. The first stream ([sharp]) is kept pristine, while the second stream ([temp]) is sent to the blur filter.
• boxblur=luma_radius=15:luma_power=3: This applies a heavy blur to the temporary stream, turning it into the background blur ([blurred]). You can increase the luma_radius for a stronger blur.
• blend=all_expr='...': This filter merges the blurred video (A) and the sharp video (B) using a mathematical expression based on the vertical pixel position (Y) and the total height of the video (H).
  • At the exact vertical center (Y = H/2), the expression evaluates to output 100% of the sharp video (B).
  • At the very top (Y = 0) and very bottom (Y = H), the expression evaluates to output 100% of the blurred video (A).
  • The transition between the sharp center and the blurred edges is perfectly linear and smooth.

Adjusting the Focus Width

If you want to widen the sharp area in the center of the screen before the blur begins to fade in, you can modify the algebraic expression using a power factor.

For a wider, sharper center focus band, use this modified blend expression:

ffmpeg -i input.mp4 -filter_complex \
"[0:v]split[sharp][temp]; \
 [temp]boxblur=20:5[blurred]; \
 [blurred][sharp]blend=all_expr='A*pow(abs(Y-H/2)/(H/2), 2) + B*(1-pow(abs(Y-H/2)/(H/2), 2))'[out]" \
 -map "[out]" -c:a copy output.mp4

Using pow(..., 2) squaring the ratio compresses the transition curve, keeping a larger portion of the center of your SDR video in sharp focus before quickly transitioning to the blur at the top and bottom margins.

Alternative: Did you mean the “tile” filter?

If you arrived here looking to tile multiple sequential video frames into a single grid layout rather than applying a vertical tilt blur, FFmpeg uses the tile filter for this purpose:

ffmpeg -i input.mp4 -vf "tile=3x2" -frames:v 1 grid_output.png

This command takes the first 6 frames of the video and arranges them into a 3-column, 2-row grid image.