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valadaptive / ntsc-rs

Free, open-source analog TV + VHS effect. Standalone application + plugin (After Effects, Premiere, and OpenFX).
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(issue possibly??) sharpening options are overly excessive #73

Closed nlolnlolnlolnlo closed 2 months ago

nlolnlolnlolnlo commented 3 months ago

sharpening this is a problem that i noticed in ntscqt as well, is there a way to tweak the ntsc-rs sharpening to more closely match a real vcr's sharpening? it seems like it extends out a few more pixels than it should

valadaptive commented 3 months ago

The sharpening "size" is tied to the VHS tape speed setting--what do you currently have it at? If it's set to SP and still excessively wide, I can try to add finer control.

nlolnlolnlolnlo commented 3 months ago

it is set to standard play, here's the image source & preset ntsc-rs_vhs-sp_v6_7_smooth.json infomercial_screen2

oisintheblue commented 3 months ago

a more noticeable difference between the real vhs images and the ntsc-rs images is how big the grayscale gradient thingy is

oisintheblue commented 3 months ago

prob because of the bandwidth scale maybe

valadaptive commented 3 months ago

If you're referring to the subtle rainbow fringe, I think that's the "Input luma filter" setting's doing. It reduces crosstalk between chroma and luma when enabled.

oisintheblue commented 3 months ago

no, im referring to the grayscale gradient thingy on the left side of the photo

oisintheblue commented 3 months ago

it looks a little big

Degamisu commented 3 months ago

no, im referring to the grayscale gradient thingy on the left side of the photo

Color bleeding. It happens when the overscan of the image is casted onto the VHS signal, and that gets smeared. I'm not 100% sure on how it works, but that's from my experience

nlolnlolnlolnlo commented 3 months ago

i'm not sure how helpful it is but i did some blend mode stuff and was able to approximate the vcr's maximum sharpening as an overlay

unsharpened image and extracted sharpening vhs_sp-soft sharpness

oisintheblue commented 3 months ago

seems like theres more horizitional sharpness going on than vertical sharpness. what if the sharpness option was split in horizitional and vertical?

nlolnlolnlolnlo commented 3 months ago

vertical sharpening is not something that would work with interlacing

oisintheblue commented 3 months ago

then dont split the option in half but instead make the vertical sharpening less than the horizitional sharpening

oisintheblue commented 3 months ago

while the sharpness option still being one thing

valadaptive commented 3 months ago

AFAIK vertical sharpening isn't a thing in VHS because all the blurring happens horizontally, that is, per scanline. I will thus not be adding vertical sharpening, and I don't think it's what @nlolnlolnlolnlo was asking for in the first place.

valadaptive commented 3 months ago

Quick update on this: I think the current bandpass filter (three cascaded constant-k filters, inherited all the way back from composite-video-simulator) is to blame. I added a slider to control the cutoff for the sharpening highpass filter, but it does almost nothing.

At some point, I'll try to add the option to use a Butterworth filter or similar instead. Hopefully that'll also increase accuracy for everything else that uses a bandpass filter.

valadaptive commented 2 months ago

I've implemented the option to use a Butterworth filter as the low-pass filter throughout, and also made the VHS sharpening filter's frequency adjustable (since it actually does something with the Butterworth filter). I've managed to get this result: butter.json

316611529-b56548ea-dae8-4391-bbd9-b7e6043ea559_ntsc

Let me know if this suits your needs.

nlolnlolnlolnlo commented 2 months ago

i completely forgot to reply but that's perfect. closing the issue now