Best Method of IVTC to use In Converting HDTV .mpg to xvid

[onesikgypo]

Hi,

I just got a new tuner card and ive been plaing around with recording some HD channels and stuff, and i was now looking to convert them to xvid, and so i was looking into the IVTC needed.

By looking at the video in DGIndex i can tell its hard interlaced - and so obviously force film will not work. The frames are like the following: IBBPBBPBBPBBPBBI

Ive done a few trials using the following script, whcih as always worked quite well for me in converting dvd's:

Telecide(order=0)
Decimate(cycle=5)

The resulting video didnt have any ghosting or jerky playback, which was good, but i was just wondering whether there was perhaps a better method/script to use, specifically when i was converting HDTV Caps?

Thanks.

[manono]

The frames are like the following: IBBPBBPBBPBBPBBI

That's got nothing to do with whether or not it can be IVTC'd. Nor can you really tell from DGIndex whether or not a regular IVTC will work. You have to examine the individual frames and look for the telltale 3/2 progressive/interlaced pattern in every 5 frame sequence. If 1080i/29.97fps and from a film source it can usually be IVTC'd. If 720p/59.94fps you only have to delete the duplicate frames since all frames are progressive already.

[onesikgypo]

OK Thanks,

What i mean by DGIndex was that it showed the video type as NTSC, rather then a xx% film.

How can i examine the individual frames? I know people have said that you can just look at the d2v file, however all i see are lines such as:

900 1 0 61914922 0 0 32 32 92 b2 b2 a2 b2 b2 a2 b2 b2 a2 b2 b2 a2

with the only relevant thing i can tell being:

FINISHED  0.00% FILM

[manono]

Some programs can open a D2V for frame-by-frame examination. Gordian Knot is one such program. Otherwise open a basic and unfiltered script in VDub(Mod):

LoadPlugin("C:\Path\To\DGDecode.dll")
MPEG2Source("C:\Path\To\Movie.d2v")

A 0% Film (100% NTSC) D2V can be true interlace, hard telecine, or something really screwy like some field blended PAL2NTSC garbage. The only way to tell what you have is by examining the individual frames.

[onesikgypo]

OK thanks,

I opened that simple avs in vdub mod, and it is the traditional 3:2 progressive:interlaced frames - which should mean it can be IVTC'd - so in that case was the script i had above the best thing to use?

[manono]

Well, use Order=0 only if it's BFF, and most DVDs use TFF. You can get the field order by running the Preview in DGIndex. Or read the DecombReferenceManual which gives detailed instructions how to determine the field order. Also, upgrade your Decomb as no longer do you set the field order in Telecide, but separately before Telecide. And adding Guide=1 is usually a good idea for hard telecined NTSC stuff. Read the manual. A current script might go:

AssumeTFF() # if it's really TFF
Telecide(Guide=1)
Decimate()

There are 2 main AviSynth IVTCs. Decomb is one (the one you're using) and TIVTC is the other.

[onesikgypo]

Hi,

Thanks for the advice

I looked in DGIndex whilst parsing the HDTV mpg clip, and it did come up as top field first, i also confirmed this the way the document recommended, by ensuring there was no jerky playback in a simple avs script with AssumeTFF().SeparateFields()

I did read the instruction manaual, and similar to yours i deduced that i should use the following script:

AssumeTFF()
Telecide(Guide=1) 
Decimate(Cycle=5)

What query i did have however, was that in the manual they specified that for fast encoding, you could turn of post processing for " a nice clean input stream". However, i'm unclear as to what exactly this is referring to?

They also recomended disabling frame displays - im assuming that this wasnt a code that could be inputted into the avs script, rather i should just close that window when it pops up when encoding is occurring.

Thankyou for all your help thus far.

[manono]

What query i did have however, was that in the manual they specified that for fast encoding, you could turn of post processing for " a nice clean input stream". However, i'm unclear as to what exactly this is referring to?

Telecide has a check after field matching to see if any interlaced frames slipped through. If it spots any it deinterlaces them. This is usually pretty strict and sometimes deinterlaces "clean" frames, so if you leave on the post processor, you might want to tweak the VThresh (check the manual). If you're pretty sure that the field matching is good (that this is a 'normal' hard telecined video, without pattern breaks and other oddities, and with no left over interlaced frames), then you might want to disable the post processor (the interlacing check) with:

Telecide(Guide=1,Post=0)

They also recomended disabling frame displays

This is pretty standard (but good) advice. You don't want to have the video playing while encoding. If using VDub(Mod) to encode, turn off 'Display Input Video' and 'Display Output Video'.