When to deinterlace

[stellars_sire]

Hi,

I have used DVD2SVCD for a while now and it seems to do everything i need quite reliably. The only thing is i have no idea how to tell if a dvd is interlaced. Is there an easy way of checking this?

Also does anyone reccomend any software that will give better/more reliable results then dvd2svcd? It does work fine most of the time but if there is something better I would like to try it.

Thanks,

Matt

[jggimi]

There's certainly nothing easier/better for the creation of SVCDs that I've ever seen than DVD2SVCD. It's the most popular encoding suite here because of it's ease of use and quality results.

You can determine when to use deinterlacing by examining the content prior to encoding. This is a manual process, rather than using DVD2SVCDs automation. You can rip a chapter, open it in DVD2AVI, and inspect a scene with movement.

If using Donal Graft's Field Deinterlace filter, having it on "all the time" will not damage non-interlaced content, as the filter will not change it. However, it will slow down processing.

For NTSC content, it's usually easier to determine de-interlacing than PAL, where conversions from NTSC or field order issues make inspection more important.

For NTSC, in general, content shot on film should be inverse telecined (or force FILMed), content shot on video tape should be deinterlaced.

For more information, click on www.doom9.org/ivtc-tut.htm

[Scandinavian]

@jggimi

"Donal Graft's Field Deinterlace filter" - Is that the one you can tick "field deinterlace" when using Gordian Knot encoding?

I have done about 20 films so far - strictly according to Doom9's GK-Guide. I never bothered about deinterlacing. Should I do that to improve quality?

Scandinavian

EDIT: I just saw jggimi answerd this in the GK forum...

[stellars_sire]

I just loaded a .vob from a dvd i was having problems with (poor quality mpeg) and it came up with 'interlaced' so i am guessing that is the problem.

From the guides I assume telecide is the best deinterlace to use?

Thanks a lot for the help

Matt

[jggimi]

From the guides I assume telecide is the best deinterlace to use? Telecide isn't a de-interlacer, though it will deinterlace after assembling progressive frames. See the Decomb help file in your Gknot ../Docs folder for more information.I have done about 20 films so far - strictly according to Doom9's GK-Guide. I never bothered about deinterlacing. Should I do that to improve quality? If your content is interlaced, "artifacts" will appear when displaying output on progressive monitors, such as a PC. More information, discussion, and lots of links can be found at www.doom9.org/ivtc-tut.htm.

[stellars_sire]

I'm sorry if i'm a bit slow with this, but i'm not sure which deinterlace to use. I'm using dvd2svcd and have the options of:

No Deinterlacing
Smartdeinterlace
Blendfields
Seperatefields/Select every (PAL)
VerticalReduceBy2 (PAL)
Telecide (PAL)
Keep Interlaced

I'm encoding an NTSC dvd. Any ideas?

Many thanks again,

Matt

[jggimi]

Regardless of DVD2AVI's preview window, which reports MPEG-2 flags (see below)...NTSC content at 29.97fps is usually in one of these formats:

1) Interlaced: Shot with a video camera, usually, every frame is interlaced, and any scene with movement will show artifacts in all frames.

2) Telecined: Transferred from 35mm film at 24 fps, approximately 6 frames are added every second. These "extra" frames are created by using 1 field from 2 adjacent frames, and in scenes with movement or at scene changes, these "extra" frames will appear to be interlaced.

3) Digital Video: It's possible to have a DV source transferred fully progressive, though I haven't seen a commercial DVD transferred this way, even though the source was shot on DV. Commercial DVDs are designed for analog video out, which is usually interlaced.

MPEG-2 frames have "flag" fields that can report what the frames are. Force FILM will use these flags, without examining the frames themselves. If the flags are correct, this is a fast, usefull method to Inverse Telecine (IVTC). Sometimes, content that is flagged as "interlaced" was Telecined. If so, it must be IVTC'ed by filters, not by Force FILM.

If you are uncertain as to the source of "interlaced" content (film transfer or video transfer), you must examine a scene with movement to determine if you should IVTC or just de-interlace.

----

About the filters you mention:

Telecide is not a deinterlacer, it is a frame recovery tool that has deinterlacing built in. If not able to Force FILM, Telecide with Decimate is a popular and efficient IVTC method.

Separate fields / select even, and verticalreduceby2 are very similar filters -- they cut your vertical resolution in half, deinterlacing by reducing content. I'd only recommend them when reducing resolution by at least that amount.

I haven't used SmartDeinterlace or Blendfields. The former, AFAIK, will be similar to Don Graft's field deinterlace, which can be interpolated or blended, depending on options. The latter, AFIAK, is blending only.

For more info, please see www.doom9.org/ivtc-tut.htm