Filter SDK/Non-clip sample

Non-clip functions in plugins

Unlike usual clip functions, non-clip functions return not frames of clip but single (scalar) value as AVSValue (variant of float, integer, boolean, string).

Numeric function example

Here's a sample from script.cpp, edited for external use (by foxyshadis, see discussion):

Code:

AVSValue Sin(AVSValue args, void* user_data, IScriptEnvironment* env) { return sin(args[0].AsFloat()); }

extern "C" __declspec(dllexport) const char* __stdcall
AvisynthPluginInit2(IScriptEnvironment* env) {
   env->AddFunction("sin", "f", Sin, 0);
   return "sin";
}

You don't even need a class/constructor, come to think of it. Include avisynth.h and that could be a whole plugin right there. (If not a terribly useful one.)

Clip to float function example

There are Avisynth Runtime functions that evaluated at every frame. They can be used inside the scripts passed to runtime filters (ConditionalFilter, ScriptClip, FrameEvaluate) to return information for a frame.

Here is sample code of plugin with non-clip function:

/*
	NonClipSample plugin for Avisynth -- a non-clip sample function for Conditional Filter

	Copyright (C) 2007 Alexander Balakhnin 'Fizick' http://avisynth.org.ru

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

	V1.0. Based on AverageLuma internal filter and SimpleSample

	Usage:
	ScriptClip(" Subtitle(String(NonClipSample())) ")
*/

//following 2 includes needed
#include "windows.h"
#include "avisynth.h"

// The function is called for every frame in conditional environment. 
// Unlike usual clip functions, it returns not frames of clip but single (scalar) value
// as AVSValue (variant of float, integer, boolean, string)  

AVSValue __cdecl NonClipSample(AVSValue args, void* user_data, IScriptEnvironment* env) 
{
   // This sample function calculate mean luma value for currect frame plane
	
	// Get function paramenters from input args array

		if (!args[0].IsClip()) // check validity
			env->ThrowError("NonClipSample: No clip supplied!");

		PClip child = args[0].AsClip(); // very first parameter is source clip

	// Get clip video information
		VideoInfo vi = child->GetVideoInfo(); 

		if (!vi.IsPlanar())
			env->ThrowError("NonClipSample: Only planar images (as YV12) supported!");

	// get current frame number

		AVSValue cn = env->GetVar("current_frame"); 
		if (!cn.IsInt())
			env->ThrowError("NonClipSample: This filter can only be used within Conditional Filter");

		int n = cn.AsInt(); // frame number

	// Get source frame and its properties

		PVideoFrame src = child->GetFrame(n,env); // source frame (smart pointer)

		int plane = PLANAR_Y; // set plane to PLANAR_Y 

		const BYTE* srcp = src->GetReadPtr(plane); // pointer to plane data (framebuffer)
		int height = src->GetHeight(plane);
		int width = src->GetRowSize(plane);
		int pitch = src->GetPitch(plane);
	
	// calculate result of our function

		unsigned int sum = 0; // init sum

		for (int h=0; h <height; h++) {      
			for (int w = 0; w < width; w++) { 
				sum += srcp[w];          // sum each byte from source
			}
			srcp = srcp + pitch; // to next line
		}


		float average = (float)sum / (float)(height * width); // normalize sum to get average
     
	// return float result as AVSValue
		return (AVSValue)average;
}


// The following function is the function that actually registers the filter in AviSynth
// It is called automatically, when the plugin is loaded to see which functions this filter contains.

extern "C" __declspec(dllexport) const char* __stdcall AvisynthPluginInit2(IScriptEnvironment* env) {
    env->AddFunction("NonClipSample", "c", NonClipSample, 0);
   // The AddFunction has the following paramters:
   // AddFunction(Filtername , Arguments, Function to call,0);
   
   // Arguments is a string that defines the types and optional names of the arguments for you filter.
   // c - Video Clip
   // i - Integer number
   // f - Float number
   // s - String
   // b - boolean

	 // The word inside the [ ] lets you used named parameters in your script

   return "NonClipSample plugin";
   // A freeform name of the plugin.
} 

Compile it as DLL like other AviSynth plugins

Not processing frames plugin with Avisynth AtExit function

This plugin does not process frames. It loads a font into Windows and automatically unloads it after avisynth is done running. To run code at the end of the script, it registers an env->AtExit procedure. See discussion. (MessageBox debug lines were removed).

/* LoadFont for avisynth
  
  Created by Shin-san of Ishin Digital Anime Fansubbing
  Special thanks to stickboy, Leak, and IanB of the doom9.org forums for the help
  Special thanks to sh0dan for his simple sample script, which this file is based on

  This code, if made public, is protected by the GPLv3, which can be found at
  www.gnu.org. I'm too lazy to copy/paste it in here

  Purpose: to make it so I can load a font into Windows and automatically unload it 
  after avisynth is done running
*/

#include <windows.h>
#include "avisynth.h"

void __cdecl UnLoadFont(void* user_data, IScriptEnvironment* env);

AVSValue __cdecl Create_LoadFont(AVSValue args, void* user_data, IScriptEnvironment* env) {

  char *file = args[1].AsString("");

  // and now load the font
  if ( (AddFontResource( file )) > 0 )
  {
     SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);

     env->AtExit(UnLoadFont, strdup(file) ); // register the procedure
  }
  else
  {
     env->ThrowError("LoadFont: Font load '%s' failed.", file);
  }
  return args[0];
}

extern "C" __declspec(dllexport) const char* __stdcall AvisynthPluginInit2(IScriptEnvironment* env)
{
   env->AddFunction("LoadFont", "c[FONT]s", Create_LoadFont, 0);

   return "'LoadFont' LoadFont plugin";
   // A freeform name of the plugin.
}

void __cdecl UnLoadFont(void* user_data, IScriptEnvironment* env)
{
  char *loadedFont = (char*)user_data;

  if (loadedFont && *loadedFont)
  {
     if ( RemoveFontResource(loadedFont) > 0 )
     {
        SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);
     }
     free(loadedFont);
  }
  return;
}

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