Video Filter Proc Amp Controls


#1

Here is a table which cross references Shotcut video filters and conventional proc amp controls.

http://www.chrisnology.info/videos/Shotcut%20Video%20Filters.htm


#2

Below I converted the web page to a post body:

This glossary cross references conventional video proc amp controls to Shotcut video filters. In some instances more than one Shotcut filter can be used to replicate a given proc amp function.

CONVENTIONAL PROC AMP CONTROL SHOTCUT VIDEO FILTER(S)
Chroma level Saturation
Hue/Lightness/Saturation -> Saturation
Pedestal/setup/offset (no white clamp) Hue/Lightness/Saturation -> Lightness
Video level/Gain (blacks clamped) Brightness
Color Grading -> Gain
Levels -> Output white
Lift (clamped whites) Color Grading -> Lift
Levels -> Output black
Chroma phase/Hue Hue/Lightness/Saturation -> Hue
Gamma Color Grading -> Gamma
Levels -> Gamma

P.S. Mainly, I just needed to insert <br> tags to fix the table after pasting.


#3

Thanks Dan. I appreciate this reformatted table.

-=Ken=-


#4

Yes, thank you for doing that.

So it is finally possible to lower the black levels using Levels -> Output black (whites clamped) or Hue/Lightness/Saturation -> Lightness (whites not clamped).

Not to ruffle any feathers, but the way these controls are arranged combined with the nonstandard nomenclature makes things, um, awkward, to use a polite word. Hopefully the table will make things clearer.

“Proc” is short for “processing”, BTW, a standard term in video work (processing amplifier).


#5

We are open to suggestions.

Do keep in mind, though… your influence seems to come mainly from traditional linear TV broadcast standards. I would predict that most Shotcut users come from a different background. So something that seems more standard to you might be less intuitive to someone else. We try to strike a balance in Shotcut.


#6

No, to anyone experienced in professional video, not just me. That includes users who come from other NLE programs. The fundamentals are the same; for example, the concept of “gamma” is the same whether in Shotcut or avisynth or vapoursynth or ffmpeg or Avid Media Composer or Adobe Premiere or Final Cut Pro or “traditional linear TV broadcast”.

There are three different ways to adjust white levels in Shotcut, each accomplishing exactly the same thing. This has nothing to do with “traditional linear TV broadcast standards” but everything to do with how Shotcut is organized.

I appreciate that. I’ve tried it, sometimes successfully, sometimes not. That said, Dan was amazingly responsive to the issue of color accuracy so that is a plus for Shotcut.


#7

Hi, you seem knowledgeable I am interested to know what determines professional video versus amateur. Can you recommend a resource for amateurs who want to do professional work?

I’ve been using different NLEs since the 90s and this is the first time I’ve heard of “filter proc amp controls”. Is this a throwback to analog editing? All the analog editing I did in the 90s involved a stack of VCRs and a cheap video mixer.

Thanks!


#8

Hi stanglow -

Interesting couple of questions.

Video technology has a long history dating back to the 1930’s when it was developed by RCA and others, and a nomenclature that has become de-facto standard. In some cases the technology and nomenclature have become codified as (U.S.) law in the Code of Federal Regulations and enforced by the FCC. Keep in mind that originally most video was distributed to the masses by being broadcast over the air.

Although the technology has changed from analog to digital, most of the fundamentals remain the same, with the possible exception of audio and video compression. Digital compression is a new technology.

I believe the main reason analog broadcast television served us so well for so many decades was standardization. As I say, in some cases those standards have been codified into U.S. law.

The bible that served me well in the analog era of video was this one:

That said, a lot of my experience comes from actually working with the equipment over the past 4 decades.

You want a book more up to date and which covers digital. I have a couple of books which I will look through to see if I can recommend any of them.

The web is full of cruft on video written by ignorant pseudo experts. One site in particular makes me tear my hair out because it has so many facts wrong.

One thing I’ll leave you with is that a proc amp has four basic controls: video level, also known as gain or white level; pedestal or setup; hue, and chroma level, also known as saturation. Among pedestal/setup, which are used to control black level, there is offset, which raises the level of the entire signal, and “lift” which only raises the dark regions while the whites remain clamped, i.e. they do not change level.

Gain is multiplicative, i.e. the video levels are multiplied by a gain factor. Pedestal/setup/lift is additive, i.e. a value is added to the video levels, not multiplied. Hue has fallen by the wayside because in digital there is no longer a phase-modulated subcarrier which carries the color information as in analog. ffmpeg offers a means of adjusting hue and the Shotcut developers were wise to support it in Shotcut.

If you have more questions, feel free to ask.


#9

Cool thanks for this info. I search online and saw an analog box with those same four controls. I wonder of it would be easy to use existing filters and code a new one that basically takes the functionality already in Shotcut but combines them into a “Proc Amp” plugin. I’ve seen this in audio DAWs where some common plugins are rolled into a VST that appeals to traditional engineers.

I’ll see if I can get my girlfriend to buy me that book for my birthday. Guys are so hard to buy gifts for, right?


#10

I think Shotcut would benefit from having some of the redundant controls eliminated.


#11

The Ennes book is obsolete. Are you sure you wouldn’t prefer something that deals with digital?

I’m not familiar with what’s out there, sorry.


#12

That is not going to happen.


closed #14

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