To Inverse or not to Inverse

[n1koolkat]

I'm fairly familiar with VCD conversion (I can't be bothered with SVCD as i tend to use rewritable disks, watch the movie and then erase them, whilst keeping the original avi movie). However lately I'm still getting a lot of conflicting information about whether to use inverse telecine or not. The majority of the avi films i encode tend to be 23.976fps. For some reason TMPGEnc tends to favour using inverse telecine in a lot of these cases (again not all cases, so i can't assume that it is defaulting to this setting).

I've read a lot of contributions to the various forum and a lot of contributions suggest that it is not necessary. Others point out of that you get a noticeably smoother picture when it is selected, and another set suggest that it should be used with 29fps encoded films. Can someone come up with a definitive guide as to the benefits of using inverse telecine and when to use it or not?

Again, i've also notices the 3:2 pulldown is often mentioned with IVT. Are the two settings to be used together. Again i'd appreciate it if one of our experts would show us the way. Looking forward to hearing from y'all.

[mategal]

telecine and 3:2 pulldown are the same

but read more about at www.lukesvideo.com
Pretty neat stuff there.

And yeah you dont need all them above when staying by NTSC. Only if you are converting from NTSC film to NTSC video ( 29.97-23.976)
NTSC video <-> PAL is a simple speed up slow down process

[SLK001]

inverse telecine and 3:2 pulldown are the same

Well, actually they are not. Inverse telecine'ing is the process of removing the extra interlaced frames from 29.97fps video to return it to the original film rate of 24fps (23.976). IVTC has to be done on video that no longer has the pulldown flags present.

3:2 pulldown (or the more common 2:3 pulldown) is the process of adding the RFF and TFF flags to a video at film rate to allow a DVD player to present the video at the proper video rate for NTSC.

However, telecine'ing and 2:3 pulldown (or 3:2 pulldown) are the same.

[wipeout]

I know the problem......I have seen improved performance by doing IV.....maybe stripping out the flags first and then repopulate with fresh new flags does help with playback.

Kind of strange...Does not make sense why the wizard puts IV in but the template does not.

[n1koolkat]

Thanks for the contributions, although I must admit that I am still a bit confused particularly as some users (Thanks Wipeout) clearly see better results using IVTC even with 23.976fps. I've come to the conclusion that I will always use it for converting 29fps but will think twice when converting 23.976fps. I also have to admit that I have'nt seen any major differences in both cases so if i have time i'll consider using IVTC as it takes twice as long. Anyway I'm off to check out Luke's contribution to the debate (thanks mategal)

[SLK001]

IVTC is only used - let me repeat that - ONLY used on 29.97fps NTSC video that originated as film (okay, sometimes 25fps PAL has an additional frame created to get from 24fps). If you try to IVTC a video at 23.976fps, all you'll get out is garbage.

[n1koolkat]

I used IVTC on a 23.976 film and it looked perfectly alright to me. But I take your point. I won't used it again. Meanwhile is it always used on 29pfs NTSC film as i've never done it before and have'nt had noticebly bad results, (then again i was'nt really looking)? I will give it a go on the next 29fps film i convert and see if it there is an improvement in performance.

[shito]

IVTC is only used - let me repeat that - ONLY used on 29.97fps NTSC video that originated as film ...

How can I tell, whether the video originated from film or not, though?

Greets
Konrad

[menace]

if you load up your AVI in virtualdub or other frame by frame software you should see a pattern of 3 progressive frames (nice looking) and 2 interlaced (passed through a comb) frames. If this pattern is repeated then your avi is telecined--whether it came from film or not is anybody's guess but is more likely as film is 23.976fps.

if you see jagged lines in every frame then your source is truly interlaced and different rules apply(i.e. IVTC will not help you here)

[shito]

@menace: Now here´s something weird: I checked the way you suggested (thanks, BTW) and the result was that every 15th (yes, every fifteenth) frame was interlaced. I checked about 600 or 700 frames and it was always this pattern, 14 progressive, 1 interlaced, 14 progressive, ...

Any clue on how this could have happened? BTW, I tried to transcode the file by frameserving with VirtualDub (resizing and smoothing in the process) to TMPGEnc standard NTSC VCD-template and the result was a jerky mpg, kindalike the movie would stop for a tiny little moment at regular intervalls. (besides, the audio was out of sync, but I guess this was due to the use of the temporal smoother-filter) Looks like the interlaced frame somehow screwed up the encoding-process.

Greets
Konrad

[menace]

No idea how that could have happened other than someone has messed with it substantially before it fell into your hands. Although with 1 out of 15 frames you could run an avisynth decomb process on it--haven't tried it myself but others report that this removes interlacing artifacts well. Also, if its that regular you could do a manual inverse telecine, but again I haven't tried that either so you may have to consult more experienced brains--sorry I couldn't be more help.

[shito]

Thanks for your help. I haven´t gone into the avisynth-direction at all and I´m not sure it´s for me, so I guess, I´ll just kick my every-15th-frame-is-interlaced-bullshit-file and get on with doing my own trans- re- enc- whatever-coding. The hint for recognizing telecined material will be helpful in the future, though. So thanks again, I really appreciate you taking the time. :thumbup:

Greets
Konrad