What does IVTC mean?

[DeVeDe]

I cant find anything about it. What das ITVC means?
And if i just reencode a BD to 25GB do i need that?
Thanks

[JJB]

I cant find anything about it. What das ITVC means?
And if i just reencode a BD to 25GB do i need that?
Thanks

I think your looking for IVTC.......Google that.

[DeVeDe]

Well yes. wrong typed. Thanks, but also Google, what i did before gives no answer, thats why i asked here.

Retyping to ask google isnt really helpfull to be honest....

[jdobbs]

Inverse Telecining.

When converting a 24fps film to a 30fps NTSC television signal, you have to have a method of conversion that doesn't look jumpy when played back. Telecining adds flags to the source that tells it to repeat and mix fields from two adjacent frames to create one new frame out of every 4. By doing it this way you don't actually have to create the frame before encoding, as it is done at playback. That can improve encode quality and reduce required bitrates.

Some people take it a step further and actually record the telecined frame as well. That is called hard-telecining.

Inverse Telecining (IVTC) simply removes the inserted frame, either by ignoring the inserted flags (pulldown flags) or by removing the inserted frame. This brings an encoding back to it's original 24fps (FILM) state.

There can be more to it than this (like converting other framerates) -- but this is by far the most common usage.

[Guest]

Google, what i did before gives no answer You've got to be joking! Here is just one of many that I found with Google in seconds:

http://wi-fizzle.com/howtos/ivtc_explained.php

BTW, I moved this out of the BD Rebuilder bugs thread because it is not a bug report.

[J_Darnley]

Google, what i did before gives no answer
That's odd. The first two results give the answer without even clicking through to the pages.

[DeVeDe]

Very friendly and helpful Community. It makes just so much fun to be with you guys. Well if you dont like helping in ANY way and i mean in any way you should not.... :stupid:

[Asmodian]

No thanks for jdobbs? Also neuron2's link is great. :(

Those look like very good answers to me.

Also did you really google ivtc? It really does give a lot of good links. The second link (for me) is to doom9 with a very thorough explanation.

[Guest]

Why are you saying that I am not helping you? I gave you a link to a simple explanation with a very useful illustration. If that is not what you seek, then please explain further.

[minaust]

I cant find anything about it. What das ITVC means?
And if i just reencode a BD to 25GB do i need that?
Thanks

IVTC is a pain in the anal orifice, but here's a nutshell:

I'm referring to the USA – European countries use a different solution due to different television standards.

For technical reasons TVs used a frame rate of 30 frames per second. But Hollywood had settled on a frame rate of 24 fps decades before. So how to put a movie on TV?

First, Plan “A” would be a no-go. The characters would move around in a madcap frenetic manner like the old silent comedies, and the audio would immediately lose sync. Speeding up the sound would make James Earl Jones sound like Mickey Mouse, and Mickey Mouse could only be heard by dogs.

Plan “B” required a little math. The frame rates, 24 and 30, what is the least common denominator? The answer is of course 6. 24/6 = 4, 30/6 = 5. So 4 frames of film need to become 5 frames of video. So, in ye olde days of television the process was to simply repeat every fourth film frame as a fifth video frame. This worked – sort of. Any movement was jerky, but at least it was playing at a normal speed & the sound was in sync.

Then came Plan “C”. The smallest increment of film is the frame. Video can be broken down one step further, into fields. Each video frame consisted of two fields: even and odd. A process was developed to swap and borrow fields between frames to synthesize a fifth frame for video. This greatly alleviated the jerkiness problem. This is called “telecine”. If you step through a telecined video, you'll see a pattern of three clean frames, followed by two interlaced ones that look like someone dragged a comb through it.

Who does this telecine? It's done in several places. For VHS and laser disk, it's done at the mastering lab. For broadcast TV, it's done at the TV station. If you're watching a DVD, it's being done right there in your DVD player. Film movies are encoded at 24 fps, and the appropriate flags are set. This tells your DVD player to do the conversion so that you can watch a movie telecined, or at its native format if you have a newer TV.

Undoing or reversing something is “inverse”, so undoing this telecine is inverse telecine, or IVTC. If you're ripping a DVD, taking care in your software settings means IVTC isn't necessary, as the telecine was never applied in the first place. But if your source material is VHS, laser disc, or a TV video capture, and that combing bothers you, then you'll need to do the IVTC. It's a two-step process. First your IVTC solution needs to identify the combed frames and then swap the appropriate fields back where they belong.

At this point you're point your video is identical to Plan “B”, above. You're still at 30 fps, and every fifth frame is a duplicate of the one before. So the next step is to “decimate” – remove those duplicate frames & reduce the frame rate to 24 fps. The audio is still in sync.

Any decent IVTC solution performs both steps & does it in one pass.

Disclaimers:

1. There are several different telecine schemes, depending on the frame rate conversion needed, and each requires a different IVTC process.
2. Not all DVDs are encoded as I described. It's got to be region 1 with a film source.
3. Hollywood hasn't always used 24 fps as their standard. The old silent films may be at 16 or 18 fps, and one experimental format (Todd-AO) used 30 fps.
4. The actual frame rates are 23.976 & 29.97. 24 & 30 are close enough for government work.

Your mileage may vary.

BTW, I Googled 'IVTC', just those four letters, and got back half a million hits.

[CruNcher]

DeVeDe

Here is a nice Visual Explanation (Video)
http://www.hqv.com/index.cfm?page=tech.cadence