The bad chroma (blockiness) has occurred because the frame was thought to be progressive when it was actually encoded as interlaced frames (or vice versa) and so the colour samples are decoded incorrectly. Some DVD players suffer from this problem too. If you do see this problem it is most common when you do a colourspace change you will want to put "interlaced=true" inside the parenthesis such as:

ConvertToRGB32("Interlaced=true")

When you get this image, you may want to use the right arrow cursor key to scroll through the footage frame by frame. One of the images will have ordinary looking motion and the other one will jerk back and forth in a really obvious manner (note that both will have a little vertical jitter, but that's natural). The smooth one is the correct field order - Top Field First or Bottom Field First (some editing programs refer to this as Upper first or Lower first but it's the same idea).

This is important to know this because:

1) If you IVTC with Decomb 5 you will need to specify a field order. This is what you need the Telecide(order=1) thing for.
2) If you edit interlaced footage you need to tell the field order to your editing program so it knows what to do when it adds effects.
3) If you are going to export to DV at any point then, as DV is Bottom Field First, you will have to get the field orders to match which may involve changing the field order.
4) If you are making a multi-source project (or multi-editor amv) all the sources should be the same field order.

If for any reason you need to swap the Field Order of a source, you can by using the ADSwapFieldOrder() command. This is a very simple command that removes the top line and makes a duplicate of the bottom line in order to shift everything up one. There are also avisynth plugins that can do this too.

Remember that progressive footage does not have a field order - or rather it can be displayed as either top first or bottom first and it will never matter. Thankfully, because of this property of progressive footage, it is easy to mix progressive footage into a video containing interlaced footage with a field order. However, when editing only progressive footage you should disable field processing in your editing application (in Premiere and similar programs, set rendering to "no fields") otherwise you may find your effects and fades will be processed interlaced.

Interlacing Methods: Telecine, Pure, Hybrid, Blended and Half-Blended

OK, so you now know if you have interlacing and also know what the field order is. The next thing you need to know is how this source has been interlaced so you can decide how to remove it if you want to. This is useful to know even if you want to edit interlaced footage as there are some interlacing issues which can play havoc with quality.

We aren't going to talk about how to remove the interlacing yet - this is just a description of the different types so you can know what kind of deinterlacing to do later. Read through them all and see which description best fits the interlacing in the source you have.

Pure Interlacing

Pure interlacing can occur in both PAL and NTSC sources. This process involves taking full advantage of the 50 or 60 individual fields a second that are used in PAL and NTSC video to get the smoothest looking video possible when shown on a TV. If an anime is produced in pure NTSC then it is likely to be really difficult to cleanly remove the interlacing as there are fewer full frames to restore as there are lots of fields which have a unique image.

Many modern shows are completely digitally animated and so they sometimes take advantage of this feature. PAL also uses this feature a lot as the NTSC fields are sometimes decimated to PAL numbers and reweaved into a pure interlaced PAL stream. This makes original frames much harder to find. When faced with a pure interlaced source it is sometimes not worth looking for the original frames (which is what you do with Inverse Telecine filters like decomb) sometimes it's better to just completely deinterlace them.

Telecine and Pulldown Material

If you have footage that was cell animated (the old fashioned way, not computer aided) or you have a source that was made for the cinema then there's a good chance that the footage was produced at 24fps and has gone through a simple Telecine (3:2 Pulldown) process like the one described earlier in the theory guides. If you are really lucky, this process was clean and has no pure interlaced footage at all. This is a common process used to convert FILM to 29.97fps NTSC.

PAL footage can also use pulldown (2:2 pulldown) where either both fields will be from the same image to make one regular frame or there will be an offset so that the fields go ab bc cd de where a b c and d are different images. This is easily correctable using an Avisynth plugin called decomb but frankly this method is pretty rare on PAL anime dvds (unfortunately)

Removing Telecine interlacing is called Inverse Telecine (IVTC) and is pretty easy to do in AviSynth with the Decomb plugin (as contained in the AMVapp install) which has two functions (Telecide and Decimate) that when used in succession will IVTC your source. This will be explained in detail later.

Remember, this process will only work perfectly if you have a neat Telecined source. This is actually pretty rare these days as most sources are Hybrids.

Hybrid Sources

These are sources that have a mixture of interlacing patterns. Some anime have a digitally edited opening sequence which is pure interlaced and then use a regular Telecine pattern during the episode itself. X TV and Azumanga Daioh both use this particular method. Some shows just use pure interlacing on scenes where they have added something digitally, like some CG or a title etc.. These are Hybrid sources and are the most common type for anime TV shows these days. You see, although they could make completely fluid animation at 60 fields per second it's a lot of effort. Even with computer animation the animators are too lazy to go into that much effort. Pans and other parts of animation that can be automatically created with computers are more likely to use all the fields for ultimate smoothness but there are many sections that will still be only 24, 12 or even 8 frames a second. Those parts can generally have their original frames restored.

Success in cleanly removing the interlacing in hybrid shows will depend largely on the amount of pure interlacing you have. If you don't have much, and most of the footage is a regular old-fashioned telecine then you can IVTC and your footage will be mostly pretty smooth. If you have mostly pure interlaced material you can either try full deinterlacing (smoother motion, not always as good picture quality) or you can try using the avisynth decomb filter but smoothness of motion may be a problem in parts where pure interlacing has been used to make the motion smooth (digital pans etc.).

Full Field Blended Sources

These are the scourge of PAL anime DVDs. Admittedly it is difficult, in many cases, to return to the original progressive FILM source of a show to produce a PAL version like they do with regular movies. With movies, the original 24fps FILM is found, sped up, the audio processed to match and a progressive 25fps source produced. However, many anime shows were never designed for FILM (see Hybrid and Pure Interlaced) and others just don't have FILM prints around anymore. Unfortunately when converting to PAL they have to make a 25fps output and they have to do this without making the footage all jerky.

This generaly means they don't go around removing frames to make it 25fps. Instead, many production companies take the NTSC source and blend fields together in a pattern so that the effective fps is reduced from 29.97 to 25. This is very quick and convenient for the production studios but intensely irritating for an amv creator wanting a nice clean source to deal with. This is especially annoying when there is a perfectly good progressive master around and they have just not used it. You can look at the individual fields of your source in Avisynth by using the command SeparateFields() - if you have a full field blended source it will look something like this field from the Dutch rental version of Spirited Away, which is a blended field decimation of the Japanese release:


This is just one of the fields, not the whole frame. The whole frame together looks even worse, especially when you have two fields that are blended in succession from three or four different source fields. What irritates me most about this image is that I have the Japanese release and know that it is progressive and can use Force FILM on it. This means that I could have easily converted 24fps to 25fps, processed the audio to match and made a better PAL dvd than this Dutch production company... and these people get paid to do this. Cheapskates :P

This blending decimation causes many problems for interlace removal. If you deinterlace this footage, you will end up with blended frames which both look ugly and are hard to compress. This can be very annoying for an editor using PAL sources as the majority of them use this technique.  This is one of the reasons that despite living in the UK I only ever purchase NTSC anime sources from the USA, Japan, Hong Kong and Korea. NTSC sources have their problems too, but at least *most* of the problems of NTSC can be solved.

Restoring the original frames when you have a blended source is very difficult and although attempts have been made to try and correct this kind of source, nobody has yet come up with a completely successful way of doing so. There have been some custom filters that can help, however, and investigations into this problem can be found in the following threads on Doom9.org:

http://forum.doom9.org/showthread.php?s=&threadid=66093

http://forum.doom9.org/showthread.php?s=&threadid=61792

http://forum.doom9.org/showthread.php?s=&threadid=49815

You may want to start by trying unblend which is contained in the AMVapp and are documented in the Avisynth Filters/Documentation folder.

It is sometimes possible for NTSC footage to have full-field blended footage too, Sometimes this is produced when making a Telecine - being used as padding between regular frames. Luckily IVTC in decomb is pretty good at eliminating these provided all the original frames are there and the blends are just duplicates of frames that are also shown unblended. However, if there is an image which only exists as part of a blended frame then, like the PAL source, a deblending method would need to be used to try and restore the footage. You can try IVTC with decomb's filters on this sort of footage but you may either have blended frames or jerky motion depending on the Decimation process you choose.

Partial Field Blended Source

Just when you thought that full field blended sources were the worst you could get, along comes something that takes it to the extreme. You see, when converting FILM sources to NTSC a studio would have to use a Telecine process and some Telecine processes are good and some are bad. The good ones are clean, tidy and can be IVTCed - the original frames can be constructed by sticking fields back together and everyone is happy. However, there are nasty ways of doing Telecine. One is the full field blending technique described at the end of the last section, which is bad enough but then there are two which are even worse than full field blending:

One Field, Two Halves of Two Images: The FILM footage is projected onto a screen and then sampled (a process which captures the scanlines in order) by another camera at 59.94 fields per second. This Telecines the material to the full 29.97 frames per second. This is ok except that sometimes when a field is being sampled the original projected frame changs from one image to the next halfway through sampling the field.! THe camera sampling this then ends up with a field where the top half of is from one image and the bottom half is from the next! The Avisynth filter PeculiarBlend() was written to remove this but to be honest it's not very common in anime sources... a more prevalent method is this...

Temporal Scanline Blending: The FILM is converted to NTSC using a telecine device that samples each new field by scanning down the image (if you imagine the light of a photocopier moving across a piece of paper you get an approximate idea of what happens even though I am simplifying). However, as the image being sampled changes, this causes the field being sampled to blend into the next image - this grows more and more as the sampling continues until finally the image has completely changed to the next one. This is the nastiest of the nasty Telecine methods and can be seen in every Gainax production from Otaku no Video to Kare Kano and in many more late 80s to late 90s anime. It's the reason Eva Renewal had to be made. What you get is fields that looks like this:

Field 1:

Field 2:

U-G-L-Y. If you look at field 1 you will notice that the blending of the two images only begins in the bottom half of the field and by the time you get to the bottom you are more in the second image than the first (see the guys foot on the right). This is the telecine device blending the scanlines more and more with time until they are in the next image and through to the next image then the next as the image is scanned.

This stuff is nigh impossible to recover at the moment. There are no tools available at our level which can deal with field blending like this, the best you can do is try IVTC and hope to god you don't get too many blends and that the motion smoothness isn't totally ruined. When making my Gunbuster video I had two IVTC patterns, one without blends that was jerky in panning shots and one with blends that was smooth in panning shots and I had to use the different sources for different parts of the video depending on the scene. It's nasty stuff - especially in pans where you can end up with an IVTC process giving you a scene with horizontal motion with the top half moving in one frame and the bottom half catching it up in the next frame. Evil.

There's only one thing worse than this kind of blended field Telecine - PAL anime which has converted this blended field Telecine to PAL by blending the fields even more! I haven't seen the PAL Evangelion print but from what I've heard it sounds like a mess.

This means that the video is using all of the available quality of the DVD and it also means that widescreen TVs only have to stretch the image horizontally - which is also good for quality.