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How to properly identify and process interlaced video.

Telecined Video

Some DVDs may contain videos which may be interlaced. In order to process the videos, they must be converted to progressive by deinterlacing. However, not all videos which looks interlaced are actually so. Most NTSC videos are videos which have been telecined from film and they should not be deinterlaced.

There are a few ways to determine the exact nature of the video.

In DGIndex, press F5 to preview the video. In the information window, if the Video Type is detected as Film, then you can select Forced Film from the Video Field Operation menu and save the project.

NTSC Film

But sometimes, the video may be identified as NTSC, but still be telecined material.
In order to properly identify the video, you can open it in VirtualDub and examine each frame.

A telecined video will contain a mix of interlaced and progressive frames.
In this example you will see that frame 1-2 is interlaced, followed by 3-4-5 which are progressive, then 6-7 interlaced, and 8-9-10 progressive.

TIVTC is an AviSynth filter which can be used to restore progressive frames from telecined videos identified as interlaced.
Just download and extract TIVTC.dll it to your C:\Program Files\Avisynth\Plugins folder.

Use the following AviSynth command to IVTC this type of video:

tfm(mode=5,pp=0,slow=1)
tdecimate(cycle=5)


The result will be a progressive video with 23.976fps.

PAL Euro Pulldown

PAL videos may contain a so called Euro Pulldown which will look like 12 interlaced frames followed by 13 progressive frames.

Use the following AviSynth command to IVTC this type of video:

tfm(mode=5,pp=0,slow=1)
tdecimate(cycle=25)


The result will be a progressive video with 24fps.

Interlaced Video

For interlaced video, in order to process it properly such as denoise or resize, the video must be converted to progressive by a process called deinterlacing.
Always remember that in an interlace video, every frame will be interlaced. If the video cotain a mix of interlaced and progressive frames, it's usually a telecined video and should not be deinterlaced, but IVTC in order to restore the progressive frames.

First, one should always verify that an interlaced video has the correct field order. Put this at the end of your AviSynth script and open it in VirtualDub:

SeparateFields()

A video with correct field order will look like this.

If the video contains wrong field order, the movement will be in wrong order and video will look like this.

To correct the field order, put this in your AviSynth script. It is important that this line comes before deinterlacing.

ComplementParity()

Deinterlace with QTGMC

QTGMC is a very high quality deinterlace filter for AviSynth. It's very slow but produces excellent quality. Please follow the installation instructions for QTGMC here: http://forum.doom9.org/showthread.php?t=156028

To use QTGMC, add this line to your .avs file:

QTGMC(Preset="Slow")

You will get a video with double frame rate. For example, for PAL video, you will get 50fps video.
If you for some reason would like to keep standard frame rate, you can add this command instead:

QTGMC(Preset="Slow", FPSDivisor=2)

You can experiment with different presets, which will be faster but may produce lower quality.
Slower, Slow, Medium, Fast, Faster

After deinterlacing, the video will be progressive and ready for further processing.

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