WELCOME TO THE IVTC SHRINE

Kardos' Guide to IVTC for SVCD MUSIC VIDEOS and TV SHOWS.

Part 1: What is this 'IVTC'?

IVTC means InVerse TeleCine. IVTC is the technique used to reverse the telecine process: telecining is the conversion of 24fps film video into 30fps video for broadcast. Inverse telecine is the reversal of that process from 30fps broadcast video to 24fps. This page is designed to help you use IVTC on your captures, and thus have better quality results. If you want to know more about telecining, you should read this site:

Nicky Pages' Digital Solutions

Part 2: Why IVTC? The advantages of IVTC are:

You don't have to deinterlace

Deinterlacing with "double" results in blur and ghosting effects. This is *NOT* fixable by using a ghost-reducing filter, or by using a sharpen filter. [Screenshot]

Deinterlacing with "even" or "odd" field results in notchyness on diagonals, and an effective vertical resolution of 240, not 480. [Screenshot]
More bits-per-frame
Obviously you can achieve better quality (less blocks, more sharpness) by having a higher bits-per-pixel (BPP) rate. The standard SVCD bitrate is 2.52 mbps.... if that is used for 30 frames, the BPP will be 0.36, while the BPP for 24fps will be 0.46. This also equals 25% more bitrate for 24fps. The biggest misconception here is that frame are getting deleted.... This is also beneficial because you can increase quality without using "x-svcd" (nonstandard svcd), and thus not break the svcd standard.

The disadvantages of IVTC are:

It takes more time than a simple deinterlacer
Not all video is "IVTC-able"

Part 3: OK, sounds good, what do I need?

You need:

Tsunami Encoder [www.tmpeg.com]

I realise that there is some software that "supposedly" can do IVTC. As far as I know, they can't handle changes in the telecine pattern, so they can only be useful if your video has a fixed telecine pattern. I also realise that Tsunami encoder has an "Auto IVTC". This automated IVTC scans your video searching for interlace lines to identify the proper frames to use. This is very imperfect, and don't recommend it, because it will always get a bunch of frames wrong. You will need to manually fix them, so it doesn't save you time. The only way to IVTC is manually. :)
Some NTSC source video:
If you plan to encode as SVCD, use 480x480 or 704x480 source resolution, and your frame rate must be 29.970 fps. If you are capturing with a tv card, you should not have dropped frames. Dropped frames decrease your effective framerate and screw up your IVTC pattern. If you have a dropped frame problem, defrag your hard drive, close as many running programs as you can (even virus scan for the duration of your captue), and dont use a 486. A fast hard drive (7200rpm), and at least a P2 is good for capturing SVCD video.

Part 4: OK, I have the stuff, what do I do?

First, you must determine if your video is "IVTC-able". Tsunami encoder is the best tool to do this. Load your video as the source video, and load the "Super Video CD (NTSC-Film)" preset. Then press the settings button, click the advanced tab, and double click on "Inverse Telecine". Then click on the first frame, and begin scrolling right, using the -> key. As the frames scroll by, examine them, to see if they are interlaced or not interlaced (progressive). You should be able to find the the following pattern:

Progressive, Interlaced, Progressive, Progressive, Interlaced

(For now on I will abbreviate this pattern as PIPPI)
If you see this pattern, then your video is IVTC-able. If you see weird patterns, exit the IVTC settings, and switch the field order. You can do this at the top of the Advanced tab. Just change A to B, or B to A. Then return to IVTC settings and search for the pattern again.

Part 5: OK, I have IVTC-able video, tell me what to do!

All right, this is the hard part. Go back to IVTC settings, and press the Clear button. This will reset any previous IVTC settings. Find the first frame in the PIPPI pattern, right click it, and press "Deal after this frame according to pattern". It'll ask you for a code. Enter the code: 10010
Next you use the arrow at the bottom of the BIG frame to "preview" the ivtc'd video. It will have no interlace lines, no ghosting, and no notchyness, *if* you did it right :)

Part 6: It worked, no ghost, no notches, no blur, it's perfect!

6A. Don't be so silly, IVTC is not that easy. The next step is to scroll along until you hit a scene-change. When you come to a scene change, the pattern gets interrupted. The best way to show this is with a text representation of the frame pattern:

  i) Any normal bit of telecined video will look like this:

     PIPPI PIPPI PIPPI PIPPI PIPPI PIPPI PIPPI


 ii) OK, now we can cut it and add a different clip of telecined
     video... this is what happens during a  'scene change' in
     a music video, tv show, movie, etc:

     PIPPI PIPPI PI + IPPI PIPPI PIPPI PIPPI


iii) The result (in this example) is:
     PIPPI PIPPI PI IPPI PIPPI PIPPI PIPPI
            ^^ ^^^^

As you can see, the nice and simple PIPPI pattern is all screwed up. The code that you apply to a normal PIPPI pattern is 10010... so when you get a cut, you have to adjust it a bit:


     PIPPI PIPPI PI IPPI PIPPI PIPPI PIPPI 
     10010 10010 10 0010 10010 10010 10010

I hope this is easy to follow.

6B. Sometimes, during scene changes, the IVTC pattern will be severely disrupted. To compensate for this, you will need to select an interlaced frame and deinterlace it. The best deinterlace to use, in these infrequent situations, is "even field" or "odd field". I realise that this defies the law of perfect IVTC... but I don't know a better way to deal with such situations (yet). If you know, please email me. =) [kardos@kardos.cjb.net]

6C. Finally, the last part of this section. Since IVTC involves alot of frame modifying, it is only logical to expect audio desyncronisation. If your IVTC is right, then your audio will not be desyncronised. The Tsunami encoder has a feature that you can use to check if your IVTC frame selections will cause desync.. just press the Check button on the left of the IVTC settings. If it says no desync found, then you are doing a good job. If it does say there is a desync, it will jump to the point of sync-loss. This usually happens as a result of a scene-change ivtc-pattern disruption. Part B of this section deals with scene change disruptions.

Part 7: Misc stuff

What happens if I get the pattern PIPIPI?
That means your video is progressive NTSC 30fps. IVTC for 30fps progressive video is impossible, because you cannot reverse the telecine on video that has not been telecined. However, since it's not telecined, you can avoid deinterlacing. To do this, load the "Super Video CD (NTSC)" preset, and go to the IVTC options. You can use the IVTC tool to force-encode the progressive video progressively. Select the first progressive frame, right click it, press "Deal after this frame according to pattern" and apply the code: 10 Then use the scroller at the bottom to preview. Also, make sure to set the pulldown menu at the left to 30fps, when doing this special case of pseudo-IVTC.
What about IVTC for PAL?
IVTC for PAL doesn't exist. This is because PAL is 25fps, and IVTC means reversing 30fps into 24fps -- obviously impossible. However, some PAL video is progressive. This is similar to the progressive situation for NTSC. If you find the PIPIPI pattern in your PAL video, you can use the IVTC tool in the same way as with NTSC. Use the "Super Video CD (PAL)" preset, apply the code 10 from the first progressive frame, and make sure the pulldown box on the left is set to 25fps.
What if all of the frames are interlaced?
Switch the field order. If that doesn't help, then you can't IVTC your video. This is common for videos that have been converted from PAL->NTSC or NTSC->PAL. As far as I know, deinterlacing is the only way to deal with it. If anyone knows how to reverse a PAL->NTSC conversion or a NTSC->PAL conversion, (using software), please email me :) [kardos@kardos.cjb.net]

Last Updated: 03 May, 2002.