How to fix Chroma Bleed with AviSynth?

[VideoFanatic]

Is there any way to automatically do that? I tried FixChromaBleeding() but it only fixes the worst effected areas.

If not, is there any easy way to manually fix it?

[jagabo]

ChromaShift()
MergeChroma(awarpsharp2(depth=#))

[themaster1]

recently i've fixed a chroma bleeding on a vhs cap like this:

mergechroma(aWarpSharp(depth=10, thresh=0.75, blurlevel=3, cm=1))
turnright()
mergechroma(aWarpSharp(depth=5, thresh=0.75, blurlevel=2, cm=1))
turnleft()


fixchromableeding is not that good imo

[VideoFanatic]

Here's a sample video which has color droop on the ropes. I would like to fix that. Is there any way I can do that preferably with something that won't crash when in multi-threaded? I tried the suggestions and I looked at the ChromaShift documentation but I can't seem to fix it.

[sanlyn]

Many Avisynth filters will not work in MT mode.

[jagabo]

ChromaShift(l=-6) looks about right for the ropes.

[VideoFanatic]

Thanks Jagabo. That's perfect. What documentation mentions that as I looked at this page and I couldn't even see that parameter? Do you know if ChromaShift is stable in multi-threaded or not. If not, do you know of anything similar that is?

[sanlyn]

The examples on that page show how to shift left, right, up, down, and by color channel.

[jagabo]

The examples on that page show how to shift left, right, up, down, and by color channel.

Though the text never explicitly says L is used to shift up or down.

[sanlyn]

True. I don't think it says what plus or minus mean, either (or maybe it does, I haven't noticed). With a lot of plugin docs you have to do some mental "motion interpolation" to get there. First time I saw that page I was looking for a way to make colors move downward. It took an effort to realize that "L" probably means "level" rather than "height". Or maybe L is the first letter of a foreign word for height? Maybe "L" means "Latitude"? Beats me.

[jagabo]

I think L is for lines. As in "move the chroma up N lines."

[sanlyn]

Yeah. "L" is probably plain English for "Lines" . Must be time for a coffee break.

[manono]

If not, do you know of anything similar that is?

See if this works multi-threaded. No outside filters needed:

A=Last
B=A.Greyscale()
Overlay(B,A,Y=-6,Mode="Chroma")

[jagabo]

Or more simply:

Overlay(GreyScale(last), last, y=-6, mode="chroma")

[manono]

Overlay(GreyScale(last), last, y=-6, mode="chroma")

Cool, thanks.

[VideoFanatic]

Thanks guys. That's even better. Is there something easy like that I can use to fix chroma bleed instead of FixChromaBleeding() ?

[sanlyn]

I haven't found FixChromaBleeding() to be effective. The methods mentioned above are better.

[VideoFanatic]

Are you taking about this: Overlay(GreyScale(last), last, y=-6, mode="chroma")

I thought that just fixes colour droop?

[sanlyn]

ChromaShift() also helps with chroma bleeding. Sometimes people call it "bleeding" but it's really color shift to one side or up/down. Sometimes it's bleeding and shift at the same time. I have crummy videos that required both anti-shift and something to correct plain chroma blur, such as the overlay suggested or something like MergeChroma(aWarpSharp2(depth=30).

[VideoFanatic]

Is there a non-filter alternative for fixing chroma bleed like the overlay method used to fix colour droop? The color bleed looks like it's in all directions.

If I were to use ChromaShift is there any paricular script I would need or would I just need this?: ChromaShift()

[sanlyn]

Can't say without a sample. ChromaShift has to be told how far up/down, left/right you want to correct, and what color channels you want moved.

[VideoFanatic]

Hi, Sanlyn. I forgot about this thread. I have a sample now. Here's a short MPEG2 which was a TV programme recorded straight-to-DVD.

I tried this script to fix colour droop but it has no effect:

Overlay(GreyScale(last), last, y=-4, mode="chroma")

Any suggestions on how to fix it?

[jagabo]

The problems in that sample isn't that the chroma is displaced, it's blurred. It's very obvious if you punch up the saturation, before chroma shift on left, after your chroma shift on right:



A more appropriate fix is something like MergeChroma(awarpsharp2(depth=25)). Same pumped up colors, before and after MergeChroma(awarpsharp2(depth=25)):

[VideoFanatic]

How would that happen. I thought things like that only happened with VHS? Is there any way to fix it?

[jagabo]

Oh, by the way, I treated the frame as progressive instead of interlaced in those samples. You should separate fields before MergeChroma(awarpsharp2(depth=25)) then weave them back together. You may have to tune the depth parameter.

[sanlyn]

How would that happen. I thought things like that only happened with VHS?

VHS is where that video originated.

Is there any way to fix it?

Sorry, but severely over-saturated reds on VHS recorded to lossy digital format with no intermediate cleanup phase.....it's defects are digitally immortalized. Jagabo's suggestion with awarpsharp is used often. You might try one or two doses of it, but don't expect miracles.

[jagabo]

Note the over saturation in my pictures was intentional -- to make it easier to see the color bleed. The MPG file wasn't over saturated like that.

[sanlyn]

Aaaaaah. pretty sneaky. You just saturated the reds? In the sample I see some red bleeding and rather noisy red that tends toward pink. I just found a couple of things to be a bit tricky, like a closed-caption text audio track and some other text. Even in the original, reds are blooming and bright whites are blown away. Just doesn't look like TV-to-DVD source to me, but.............

[VideoFanatic]

Thanks Jagabo, your script worked perfectly. Do you know if it's stable in multi-threaded? Is there a non-plugin script I can use to achieve the same thing such as something like this which I use to fix colour droop?: Overlay(GreyScale(last), last, y=-4, mode="chroma")

How can you tell it's VHS? I thought it was straight-to-DVD. Standard Definition satellite TV is broadcast in low bitrate these days which is why it looks compressed (I once copied and pasted an unencrpted show from my satellite box onto my PC and found out the bitrate was 3 Mbps! - you only seem to get good quality on HD channels these days. If it was VHS it would have a lot more picture noise.

Could the color bleed have been caused by the video having too much colour?

[sanlyn]

The only color that's "too much" is red, and it's noisy. Overall, the rest looks undersaturated and washed out, yet stuff like the white arm- or wrist-band is washed out and has no detail at all. That's what led me to believe it might have been a VHS source. That's either a crummy broadcast image or a crummy recorder, or both. But that's just my $0.02 worth. If channels on my paid cable box looked like that I'd be switching services.

The awarpsharp routine usually works pretty well. I've had to use the statement twice in a row on some really bad bleed cases. I found that running it 3X added little, and created mild artifacts. So in a hard cleaning situation I'd say running it 2 in a row is as far as one should go.