How do you IVTC?

[magnus]

I have read every thread and cannot find a definitive answer on how to inverse telecine. I am attempting to encode a svcd and have a downloaded film source which is at 29.97 fps. I want to change it back to 23.976 and then use 3:2 pulldown when playback to increase the quality as I am hearing everyone raving about. I am also unsure as to whether or not I need to deinterlace. I checked the file in aviutil and it seems to be telecined. Sorry if this is a basic question, I just can't find a straight answer. Thanks.

[malducci]

You can use Avisynth with Decomd.dll or IVTC.dll. You can also you VirtualDub to do the IVTC. What format is the source in( i.e. avi, dvix,mpeg 1 or 2 )? Before you apply the IVTC - you have to know if the source was originally 23.976fps. If you don't know for sure that the source was originally 23.976fps, you could open the video with VirtualDub and take a look at the video frame by frame - there will be tell tale signs if was originally 23.976fps. Not all conversions are the same - if the format is in mpeg2 you can use pulldown.exe to try an remove the 3:2 flags.

[therick]

Yes, I posted some clips last week trying to solve what I thought was a field order thing, but what I now know is an interlace thing...are there any good tutorials on AVISynth? I have been looking on this site and doom9's and all I seem to find is tutorials on IVTC in TMPEGEnc...I will do it this way if I have to but I really want to see the results of this decomb thing that everybody is talking about on this site...so if anyone has any pointers on how to start with AVISynth I would be much appreciated...

[therick]

Alright, after days of searching, I have found a decent guide! Here it is for anyone who cares:

http://nickyguides.digital-digest.com/synth-vdub.htm

[magnus]

The source is in divx form. After playing it in vdub frame by frame you can see interlaced or "blurry" frames every fourth frame. If I understand this currectly this means it was a 23.976 source originally then telecined. I just don't know what to do with it now?

[malducci]

If only 1 or so frames in every 4 or 5 frames are interlaced and the rest are progessive, then you can use virtualDub to IVTC or use the Decomb.dll file with avisynth. Download the newest version of Decomb.dll at www.doom9.net, it comes with a readme file explaining the parameters - just use the default settings. Or you can download IVTC.dll and use the defaults settings as well. I'll try to reply with an example, but the best bet is to use the link provided a few replys back.

[malducci]

Are you using TMPGEnc to encode the video file? Although I don't use TMPGEnc, I heard there is an option to IVTC when encoding.

[magnus]

I am using Tmpg 2.53 plus to encode. I have heard people say it has a good ivtc when done manually but I have never seen a guide or instructions for it. I am also confused on the interlace deinterlace issue. I read somewhere if one is using svcd or xvcd with high bitrate it is unecessary to deinterlace.

[MITSUI_1]

You CANNOT properly IVTC something that has been reduced in vertical resolution. It screws up the IVTC processes used by most methods. Moreover, if you're seeing "blured" frames that appear to be combinations of two subsequent fields, then the original encoder probably deinterlaced using "blend" which also goofs up the process.

I would also point out that since the clip you've downloaded is already highly compressed, you're not going to get any quality back. The information is gone. The quality was in the original source, which you do not have. What' your doing now is the equivilent of making a VHS copy of a VHS copy. Each subsequent re-encoding of already compressed material loses more quality.

Finally, even if you IVTC your highly compressed clip, you'll just end up with the same quality frame by frame only there will be less frames and it will take 20% less space to store. You'll likely also introduce weird glitches in the smoothness of the playback since I doubt the DIVX clip has the full 480 vertical resolution needed to do proper IVTC.

Don't bother.

[malducci]

If every X-frame is interlaced, then you could decimate X-frame. As long as the there isn't a pattern change. MITSUI_1 has a point, but there are a few different ways 23.97fps is converted to 29.97fps. Most Dvix movies are progressive, so if the video does not contain the original vertical resolution, but you can see were an extra frame was created between two frames blended or field A of the previous frame and feild B of the next frame combined to make the in-between frame, then you could decimate that extra frame. There is no guarranty this will always and like I said - the movie would have to have the same pattern through out, otherwise you'll loose frames in certain parts resulting in jerky video in those parts( hybrid video ).

Why do you want to recompress it to SVCD? I have done a few Dvix movies to SVCD so I could watch it on a DVD standalone. If you do want to view it on a standalone player, then I suggest using Donald G's "smart smoother" with VirtualDub - helps get ride of some of those pesky artifacts.