Installing AviSynth with Multithreading support.

AviSynth is a versatile video editor with plugin support which enables it to perform many advance video processing tasks. Everything works by writing script commands in an .avs file, which works like an .avi file and you should be able to open the .avs file in any program which supports .avi.
In this guide we will use AviSynth mainly to frame serve MPEG2 video to VirtualDub.
The regular version of AviSynth does not yet have Multithreading support, but there's an update you can manually install to enable this.
Multithreading will enable the use of all your CPU cores and will greatly increase the processing speed of the videos.

1. Download Avisynth_258.exe and install.

2. Download AViSynth MT.
Extract out the avisynth.dll file and copy and replace the existing file in "C:\Windows\system32" or for Windows 64bit, copy to "C:\Windows\SysWOW64".

In the .avs file, to enable Multithreading, you must put this at the beginning of the file:
SetMTMode(2,0)

More information about AviSynth MT:
http://avisynth.org/mediawiki/MT_support_page

Installing DGMPGDec.

Download DGMPGDec.
Extract the files and copy DGDecode.dll to "C:\Program Files\AviSynth 2.5\plugins" or for Windows 64bit "C:\Program Files (x86)\AviSynth 2.5\plugins".

Installing Ut Video Codec

Ut Video Codec compresses the video losslessly which means there is no degradation of quality when saving. This codec supports YV12 colorspace and is multithreaded.
You can simply download Ut Video Codec
and install it.