"Combing" with some movies. Any workaround?

[MrZebra]

Ok, this is probably not a bug in Videora per say, more of a bug with the way the disk was authored but I'd like to know if there is anything that can be done about it (Using a special flag in Videora, or AviSynth)

First, I'll describe "Combing", you know how TVs are interlaced where there are actually 60 images per second with only every other lines being displayed at any given time. When movies are authored to DVD, to up the framerate from 24 to 30, it kinda exploits that to mix the frames more evenly than merely repeating every 4th frame twice.

When playing the movies on a standard interlaced TV, you don't notice anything weird. But when playing it on a progressive scan display such as a computer monitor, most of the time, the DVD is encoded in such a way that when you play it (Or convert the video), it can be rendered as a normal 30 frame video with no trailing lines.

Some DVDs, are apparently misflagged somehow and when converting them with Videora in 640x352 (The problem did not appear in 320x176) you can see those scanlines whenever something moves sideways.

Is there a special flag to add to the videora profile, or an AviSynth script that could correct this.

I have yet to play the affected movie (Only 1 so far) on my iPod or TV, so if they play fine on those, I could probably live with that, but for on the computer playback (Through iTunes) it would be nice to get around it.

[migrena]

you may try to use avisynth (http://avisynth.org/)+this (http://neuron2.net/decomb/decombnew.html)

[Sketch]

Another possibility here is creating a DGIndex project and using the "Force Film" option.

http://www.doom9.org/mpg/dgindex-frameserving.htm

[MrZebra]

Ok, after encoding a few more movies, noticed more movies are affected by this problem.

Luckily, the 35 second Dolby Digital Intro I was using to test Level settings is also affected, so I could use it to test this as well.

After getting the Decomb plugin for AVISynth and set up the script, all I get is some weird diagonally scrolling video that looks like old analog pay channels viewed without a descrambler kinda thing WITH NO AUDIO.

So is there any other way?

[Sketch]

Another possibility here is creating a DGIndex project and using the "Force Film" option.

http://www.doom9.org/mpg/dgindex-frameserving.htm
and if you have specific questions or problems on this I'll do my best to help out.

[MrZebra]

Ok, the DGIndex trick (Following the instructions on that link) did absolutely nothing, didn't give me a garbled video like the Decomb method just did the same thing as if I decoded the VOB file directly.

Ok, so now that brings up a question... What causes the garbling when using Decomb? Decomb itself OR the Other Plugin I had to use to read VOB files with AVI Synth?

So to test, I combined both methods. Did the DGIndex thing, extracted the audio track as WAV then added the Decomb command to my script...

And it worked! At least on the Dolby Digital Chopper In The City intro that I was testing it with. So I ran Amelie and A Problem With Fear through DGIndex, and made AVS files for them, A Problem With Fear is currently 41% into the 1st pass and Amelie will run after... So I'll find out tomorrow if it worked.

A Probelm With Fear was especially bad since it's a non-anamorphic DVD, so since I don't resize it (Which kinda makes the problem less apparent) it is unwatchable on a computer screen (MP4 file in QT) On an iPod or TV, the problem is not there but I want to fix it since having those misaligned images probably tax the encoder a bit and lowers the overall quality.

[Sketch]

Ok, so now that brings up a question... What causes the garbling when using Decomb? Decomb itself OR the Other Plugin I had to use to read VOB files with AVI Synth?
I am guessing the latter. What plugin were you using?

And TBH, I'm surprised the forced film option in DGIndex didn't work by itself. I've never had to use Decomb for progressive NTSC video.

[MrZebra]

I was using the Mpeg2Decoder from the plug-ins page on the AVISynth site.

Also one problem that the Dolbu Digital Intro and Amelie had and got fixed also when going through DGDecode -> AVS -> Decomb -> Videora was that the resulting video was the right size when played in QT but appeared vertically squashed on the iPod screen and the TV as if I was playing say a non-anamorphic DVD but setting my TV to do the anamorphic squeeze anyway (My TV does not support that anyway)

Another movie I made earlier had this problem too and I just deleted it at the time and decided to deal with that later, I guess I'll have to run that one through DGIndex...

[Midiman]

the resulting video was the right size when played in QT but appeared vertically squashed on the iPod screen...

This is usually a sign that the iPods widescreen option is set wrong (video settings).

[MrZebra]

This is usually a sign that the iPods widescreen option is set wrong (video settings).

Actually no, because all other movies play fine and the settings were not touched.

[Midiman]

While I don't have any solutions for you, I certainly have an explanation. You're experiencing a problem with the way interlaced video is constructed and how it is rerendered. Most people know that NTSC video (not film) is comprised of roughly 30 frames of video per second. Each frame is technically called a "color frame" and each frame consists of two "fields" which are alternately displayed. One contains all the even lines and the other all the odd lines. The problem you are having occurs when the wrong field is rendered first. Many applications give you the option of rendering the even or odd fields first... which eliminates the problem.

[msopnet]

Sorry if this is obvious, but did you try adding the "-deinterlace" flag to the Additional CLI parameters? I didn't see you say anything about it...

[MrZebra]

Sorry if this is obvious, but did you try adding the "-deinterlace" flag to the Additional CLI parameters? I didn't see you say anything about it...

Oh, so ffmpeg supports that directly without having to go through AVS, DGIndex etc...? I'll try that first next time I come a cross a movie that combs.