Clip Properties vs Frame Properties

[MysteryX]

I want to read a frame property during initialization to determine which filters to invoke in the chain.

I read "_ColorRange", which alter the further calls.


if (Input && !Skip)
{
int RangeMin = (255 - Range) / 2;
int RangeMax = Range + RangeMin;
api->clearMap(Args);
api->propSetNode(Args, "clip", Input, paReplace);
api->propSetFloat(Args, "gamma", 1 / 2.2, paReplace);
api->propSetFloat(Args, "min_in", SrcFullRange ? 0 : 16, paReplace);
api->propSetFloat(Args, "max_in", SrcFullRange ? 255 : 235, paReplace);
api->propSetFloat(Args, "min_out", RangeMin, paReplace);
api->propSetFloat(Args, "max_out", RangeMax, paReplace);
Input = Env.InvokeClip("std", "Levels", Args, Input);
}


I thought that frame properties would show as cliip properties but apparently not (unless I'm missing something). Reading frame properties requires a frame, which I don't have during initialization. So, how do I get _ColorRange during initialization?

Related to the same question -- also how to read it from Python scripts?

I want to ensure "_FieldBased" is not set in the Python script or throw an error. As for "_ColorRange", it could be a good idea to recalculate it for every frame in the case that different frames have it different. Is it possible to change invocation parameters on every frame?

[feisty2]

you read the property from the first frame.

auto ColorRange = static_cast<int>(Clip[0]["_ColorRange"]); (https://github.com/IFeelBloated/vapoursynth-plusplus/blob/master/include/Node.vxx#L65)

[MysteryX]

What happens if _ColorRange isn't the same for all frames?

btw you're too smart for me, I don't understand half of the keywords in your code :P Let alone how they fit together.

[feisty2]

What happens if _ColorRange isn't the same for all frames?

then you cannot handle this kind of situation during initialization. you can, however, assume that all frames have the same _ColorRange and check if that assumption actually holds in the getframe function, and raise a runtime error when the assumption fails to comply with the fact (https://github.com/IFeelBloated/vapoursynth-plusplus/blob/master/Examples/Rec601ToRGB.hxx#L28).

[feisty2]

btw you're too smart for me, I don't understand half of the keywords in your code :P Let alone how they fit together.

you don't need to know every last C++ feature if you're not a library author. I would however suggest that you take a look at C++ concepts (https://en.cppreference.com/w/cpp/language/constraints) and every usage of "auto" (https://en.cppreference.com/w/cpp/language/auto) if you want to better understand my code.

[MysteryX]

I suppose in VapourSynth you could take a PC-range clip and merge it with a TV-range clip. Is that supposed to be a supported scenario? I guess most plugins would fail to handle it.

Properties varying per frame are more for things like stats?

[ChaosKing]

Source filters use frame props to set a interlaced flag. So not just for "stats".

[MysteryX]

Source filters use frame props to set a interlaced flag. So not just for "stats".
I mean, Interlaced flag is generally fixed throughout the video. Is VapourSynth supposed to support this flag varying from frame to frame? As a plugin developer, should I aim to support that or not?

[ChaosKing]

I think you should support it ( if the frame prop makes sense). For example ffms2/lsmas also sets the pic_type props (I, P, B frame type). I saw multiple scripts that use that prop to do stuff with it / improve quality etc. The plugin dev just enables possibilities the rest is up to the user.

[StainlessS]

UK PAL TV [especially from maybe 80's], had portions in both progressive and interlaced.
One example, BBC, [5 or 6 episode] "Private Schulz", progressive Black & White [WW2 sections], and also outdoors sections, indoors Interlaced.

Here a script [does not uses properties] that I posted, and used on that series [originally did singleRate deint, then re-done as doubleRate]:- https://forum.doom9.org/showthread.php?p=1923123#post1923123
EDIT: Also allows for selective SpotLess use, on both Interlaced and Progressive sections.

EDIT: I'm also using same script [with recently added TFM(pp=0)] for Babylon5 [110 eps], @ DoubleRate

AssumeTFF
# Uncomment below if has any Perverse Telecine [eg Babylon5].
TFM(pp=0)
# and a bit of color tweaking, PRE-MC stuff (else VERY SLOW), : Added to linked script
O=Last
AutoAdjust(Auto_Gain=true).Merge(O,0.6) # un-comment if wished

PAL Bab5 has interlaced/Progressive and Perverse Telecine sections [Perverse, not too common, but I process the lot].

EDIT: To below, yes I guess, sort of. :)

[ChaosKing]

You could say IsCombedTIVTC is just an old school way of using "frame properties".

[MysteryX]

UK PAL TV [especially from maybe 80's], had portions in both progressive and interlaced.
One example, BBC, [5 or 6 episode] "Private Schulz", progressive Black & White [WW2 sections], and also outdoors sections, indoors Interlaced.
Some video formats even support that?

In that case, I'm invoking Levels before my plugin, how can I make the parameters dynamic?

[StainlessS]

Some video formats even support that?
Both mentioned sets of clips were DVD VOB.

In that case, I'm invoking Levels before my plugin, how can I make the parameters dynamic?
AutoAdjust aint bad, but really does need the Merge I used to ensure it does not overdo it.

AutoLevels, sometimes better that AutoAdjust, but I guess I botched that a bit, sometimes way overcompensates producing flashes, needs re-think.

EDIT:- I think AutoAdjust uses default temporal radius 20, whereas AutoLevels 7 [might have been 5 originally], I think, probably makes quite a difference.
(Also better scene change detect required in AutoLevels, fires with flickering candle and similar).

[MysteryX]

AutoAdjust and AutoLevels adjust based on frame content. I just need to make sure that TV-scale and PC-scale frames are treated accordingly, for the min_in and max_in parameters of Levels.

[WolframRhodium]

The most efficient approach is to leverage akarin.Expr's (https://github.com/AkarinVS/vapoursynth-plugin) ability to read frame properties at runtime and implement the "Levels()" function yourself. Another way is to combine std.Levels() with std.FrameEval().

[vcmohan]

Aren"t All case naming is for plugin function names and camel case for parameters" ColorRange is all case. Thought violative of convention.