How to get current frame number in AviSynth?

[zee944]

Can anyone tell me how can I have the current frame number in AviSynth?

Within ScriptClip command, I can display it such as:

ScriptClip("subtitle(string(current_frame))")

...but AviSynth doesn't recognize a stand-alone 'current_frame'.

What I actually want to do is to increase saturation from zero to maximum during playback. The first frame is B&W, the last has the original saturation. If 'current_frame' would work, my line would look like this:

Tweak(sat=(current_frame/FrameCount)*1.00)

Could anybody help?

[Sagekilla]

Try animate (http://avisynth.org/mediawiki/Animate):


ColorBars().ConvertToYV12()
src = last
start_frame = 0
end_frame = 99

src.Animate(start_frame,end_frame, "Tweak", 0,0.0, 0,1.0)

[J_Darnley]

Cast the frames to floats so that you don't use integer division and then put it all in a ScriptClip().
ScriptClip( "Tweak( sat=( float(current_frame)/float(FrameCount) )*1.0 )" )

[Gavino]

...but AviSynth doesn't recognize a stand-alone 'current_frame'
current_frame is only visible within the run-time environment provided by filters such as ScriptClip.

Hence J_Darnley's solution is closest to your original idea (though clearly the 1.0 is redundant). However, for a case like this, I prefer Sagekilla's approach with Animate.

[IanB]

MergeChroma(FadeIn0(100))

[zee944]

ScriptClip( "Tweak( sat=( float(current_frame)/float(FrameCount) )*1.0 )" )
Thank you for all of you. This one worked damn perfectly, so I didn't even try the others! :)

[stickboy]

The other approaches are better...

[Sagekilla]

If you look at it speedwise, I believe IanB's would be the fastest. A copy of the chroma channel is faster than multiplying the saturation by some float (which is calculated based on what frame you're on and the total frame count, another calculation) I think.


I think all methods are fast enough that decoding is slower still, though.

[stickboy]

IanB's is also the most AviSynth-like.

The ScriptClip way encourages wrong thinking.

[Sagekilla]

Not to mention the most elegant for that matter, No need to futz around with worrying about types or anything. Just two function calls :)

[blausand]

To be honest, the absence of current_frame still really gets me down from time to time. And stickboy, i agree that all of these Scriptclip-solutions feel conceptually wrong whenever i hassle around with them.

look at this:
clp = AVISource("some.avi")
import("someNumberedStrings.txt")

index = ((current_frame+3) % 20) > 10 ? int(current_frame/20) : 0

topSlate = Eval("topslate_"+string(index, "%03d"))
bottomSlate = Eval("bottomslate_"+string(index, "%03d"))

subtitle(bottomSlate, align=2)
subtitle(topSlate, align=8)
I need some math-munging to evaluate the right slates. Then i tried to put everything in a function.
Both approaches yield the error: "I don't know what 'current_frame' is."

I also tried to relate current_frame to a clip: clp.current_frame, and that yields:
"There's no function named 'current_frame' "
And even wrapping everything in FrameEvaluates didn't solve anything.
Is there no workaround to get a current_frame integer based on a specified clip?

[Gavino]

Is there no workaround to get a current_frame integer based on a specified clip?
It normally makes no sense to talk of the 'current' frame of a clip because Avisynth deals in complete clips, not individual frames.

The only place it does makes sense is inside a "run-time" script as processed by ScriptClip, as these are (re-)evaluated for every frame of their surrounding 'normal' script. Even here, the processing required can most often be done without caring what the actual frame number is.

See here (http://avisynth.org/mediawiki/ConditionalReader#Returning_Strings)for an example of how to solve your problem using ConditionalReader.

[stickboy]

To be honest, the absence of current_frame still really gets me down from time to time. And stickboy, i agree that all of these Scriptclip-solutions feel conceptually wrong whenever i hassle around with them.

...
subtitle(bottomSlate, align=2)
subtitle(topSlate, align=8)
I need some math-munging to evaluate the right slates. Then i tried to put everything in a function.
Both approaches yield the error: "I don't know what 'current_frame' is."

I also tried to relate current_frame to a clip: clp.current_frame, and that yields:
"There's no function named 'current_frame' "
And even wrapping everything in FrameEvaluates didn't solve anything.
Is there no workaround to get a current_frame integer based on a specified clip?Why do you need current_frame at all? Why not use ApplyRange?

[Gavino]

Why do you need current_frame at all? Why not use ApplyRange?
ApplyRange won't do it easily because he wants the thing to be dynamic.
But it could be done with Animate something like this:

function DoTitles(clip c, int index) {
topSlate = Eval("topslate_"+string(index, "%03d"))
bottomSlate = Eval("bottomslate_"+string(index, "%03d"))
c
subtitle(bottomSlate, align=2)
subtitle(topSlate, align=8)
}

import("someNumberedStrings.txt") # needs to declare strings global
nTitles = ... # no of titles
start = ... #start frame
end = ... #end frame
clp = AVISource("some.avi")

Animate(clp, start, end, "DoTitles", 1, nTitles)


@blausand
Instead of thinking in terms of current_frame, it is usually better to use a built-in filter that produces a dynamic effect, eg Animate, FadeIn, Dissolve, etc.