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Convert PAL to NTSC video
The following example will illustrate what is discussed in the "converting PAL to NTSC" article that you can find on this site. Processing of video will be made with a scripting tool called "AVISynth". If you are not familiar with it, I encourage you to review the "AVISynth Guide", also available on this site. This example will also make use of frameserving through the VFAPI proxy codec.
Tools needed to follow this example:
- VirtualDub
- AVISynth
- DVD2AVI
- VFAPI Codec & Reader
- ReverseFieldDominance filter for VirtualDub
We will attempt to convert a PAL source that was acquired from a video camera. Its characteristics are: MPEG-2 format, 720x576 resolution, 50 fields / second. Note that only the video part of the conversion is covered here.
1. VFAPI frameserving
The first step is to convert the MPEG-2 video to AVI format, which is required for editing with AVISynth. But we want to avoid creating temporary uncompressed AVI files, because they take a lot of hard drive space. So we will use VFAPI frameserving instead. It works by creating a dummy, proxy AVI file which has "VFAPI Reader" as a codec. MPEG-2 video is decoded on-demand as the AVI-proxy file is accessed. Note that since it uses a system-registered video codec, any program can read the resulting AVI-proxy file, unlike VirtualDub's VDR or AVISynth's AVS proxy files.
So we begin by starting DVD2AVI and opening the source file ("Pal_Source.m2v").
Make sure that [ Video is set to 'None', then export a project file
using 
Field Operation ] [ File .
Save Project ]
Save the project as "Pal_Source.d2v". Next, open the VFAPI
reader and import your D2V file using [ Add Job ].
Keep all settings as they are. Finally, press [ Convert ] to
create the AVI-proxy file.
2. Video processing
Now that we have an AVI version of the original file, we can start writing an AVISynth script that will do the conversion process. Open a text editor and save the empty document as "Pal_Source.avs". Open also VirtualDub so that we can later have a preview of the resulting video as we add AVISynth commands.
Since PAL
NTSC conversion requires the field dominance to be reversed, we start
by importing my "Reverse Field Dominance" filter into AVISynth:
function ReverseFields(clip clip, int "ShiftDown")
{
LoadVirtualdubPlugin("ReverseFields.vdf", "_ReverseFields")
return clip._ReverseFields(default(ShiftDown,1))
}
The VDF file has to be in same directory as the script. Then, we open the source video (the AVI-proxy):
(...)
