Modify YUV Channels in FFmpeg with lutyuv

This article explains how to use the FFmpeg lutyuv filter to manipulate individual Y (luminance), U (blue-difference chroma), and V (red-difference chroma) channels of a video. You will learn the basic syntax of the filter, how to target specific channels using mathematical expressions, and see practical examples for adjusting brightness, contrast, and color.

Understanding the lutyuv Filter

The lutyuv filter applies a Look-Up Table (LUT) to the YUV channels of an input video. It allows you to modify the pixel values of each channel independently using specific mathematical equations.

The basic syntax for the filter is:

lutyuv=y='expression':u='expression':v='expression'

In these expressions, the keyword val represents the original pixel value of the channel currently being processed. For standard 8-bit video, these values range from 0 to 255. For chroma channels (U and V), the neutral (grayscale) value is 128.

Modifying the Y (Luminance) Channel

The Y channel controls the brightness and contrast of the video without affecting the color hue.

Adjusting Brightness

To increase the brightness, you can add a constant value to the Y channel. To decrease it, subtract a value.

• Increase brightness:

  ffmpeg -i input.mp4 -vf "lutyuv=y='val+30'" output.mp4

• Decrease brightness:

  ffmpeg -i input.mp4 -vf "lutyuv=y='val-30'" output.mp4

Adjusting Contrast

To adjust contrast, scale the pixel values around the midpoint of the luminance range (128). Multiplying by a factor greater than 1 increases contrast, while a factor less than 1 decreases it.

• Increase contrast:

  ffmpeg -i input.mp4 -vf "lutyuv=y='(val-128)*1.5+128'" output.mp4

Modifying U and V (Chroma) Channels

The U and V channels contain the color difference information. Modifying these channels allows you to adjust saturation, tint, or completely strip color from the video.

Desaturating Video (Grayscale)

To completely remove color, set both the U and V channels to their neutral midpoint value of 128.

ffmpeg -i input.mp4 -vf "lutyuv=u=128:v=128" output.mp4

Adjusting Saturation

To increase saturation, scale the U and V channels away from their neutral midpoint (128).

• Increase saturation:

  ffmpeg -i input.mp4 -vf "lutyuv=u='(val-128)*1.5+128':v='(val-128)*1.5+128'" output.mp4

Color Tinting

You can shift the color balance by adding or subtracting values from the U or V channels. For example, adding to the V channel introduces a reddish/magenta tint, while subtracting introduces a greenish tint.

• Warm/Red tint (increase V):

  ffmpeg -i input.mp4 -vf "lutyuv=v='val+20'" output.mp4

• Cool/Blue tint (increase U):

  ffmpeg -i input.mp4 -vf "lutyuv=u='val+20'" output.mp4

Combining Y, U, and V Modifications

You can combine modifications to all three channels in a single filter chain to achieve complex color grading effects. The following command increases the overall contrast of the image while simultaneously boosting the blue tones (U channel) and slightly dimming the brightness:

ffmpeg -i input.mp4 -vf "lutyuv=y='(val-128)*1.2+110':u='(val-128)*1.3+128':v='val'" output.mp4