Decompose/Sharpen for realistic VHS effect

I was thinking, and in GIMP I can create realistic VHS effects by decomposing an image into its Luma, (Y), and color difference (Cb and Cr) component images, and fiddling with those. It would be perfectly dandy to have added a video decomposition tool to turn one video into 3 videos either YCbCr, or RGB(Preferably the former), and to be able to fiddle with each layer.

Secondly, what about a sharpening tool that has individual X and Y adjustments, so you can sharpen vertical lines without sharpening horizontal ones.

Any ideas on how to decompose a video, or etc??? 01-05-2024

Hi @Beauregard42

Can you provide screen captures of before and after creating the effect in Gimp.

And more details about what filters or tools are used to decompose an image into its Luma, (Y), and color difference (Cb and Cr) component

I did try something similar in Shotcut some months ago. I was more aiming at simulating an old TV screen (cathode-ray tube) effect but some of the filters I used could work for just a VHS effect, I guess.

Here are a couple of variations of that CRT effect.


Here are some of the before and after images I chose for this.

Mainly, decomposing an image into its parts just requires a bunch of math to convert RGB into YCbCr.




Here’s a pic of what the VHS sharpening effect looks like. Creates black streaks on the right edge of bright-to-dark transitions, and white ripples on the edge of dark-to-bright transitions. In the hardware, this is used to make up for the bandwidth reduction caused by the hardware in order to fit the video signal onto the tape.

The color bleeding effect can be seen in this image, where the brightness signal is roughly preserved, but the color signals have even lower bandwidth than the luma, so they blur out over vertical edges, and cause the fringing along the lines. I’ve tried, but this doesn’t seem to be possible with RGB split.

Also, what about interlacing??? The picture is scanned, 240 lines, every 60th of a second, but every other scan is offset, so that it does even lines, then odd lines, and so forth. On motion, this causes a kinda horizontal combing effect on moving objects.

And howabout the head-switching artifact at the bottom, that causes the last few lines of the active picture to be garbled.