Is it worth me deinterlacing?

[sidders]

I'm capturing some music videos from an interlaced source. I am enoding these to MPEG2 to write to DVD. I will be occasionly watching these on the PC but mostly will be watching on the TV.
Is it worth me deinterlacing, as the TV will correct this for me? Do the deinterlacing tools (e.g. VirtualDub) do a better job deinterlacing than leaving it up to the TV to do the correction?
Lastly, do I lose any quality by deinterlacing?

Sorry if these questions are straightfoward, I'm pretty new to this capturing lark.

Cheers.

[SimonSez07]

the tv doesnt actually deinterlace the video. it displays the content interlaced, which is more suited to its method of producing the image anyway, so will look better than displaying progressive frames (the motion will be more continuous, less choppy).

therefore, i would leave the content interlaced and it will display top-notch on the tv and whenever you view it on your pc, the playback software will probably deinterlace anyway, so no need to do it before encoding.

[bb]

I wouldn't deinterlace an interlaced source for DVD encoding.

But if the video is phase-shifted only, i.e. the source material is in fact progressive and the original progressive frames can thus be reconstructed without loss, I'd go the progressive way (using Telecide()).

bb

[sidders]

Thnaks for all your replies people. I wouldn't of thought that videos from MTV are originally progressive are they? If not, i am not gonna bother deinterlacing then.

[Swan]

On MTV Europe (and Vh1 Europe) the majority of videos are interlaced.
Of the American videos they show almost 95% have blended fields (badly converted from the US NTSC system to the European system PAL). Do not deinterlace, sidders. The few progressive videos I have captured on MTV/VH1 have all been phase-shifted and I wonder if using telecide on those would really make that much of a quality difference on your final DVD-quality Mpeg-2 files. I doubt it. Don't deinterlace is my advice.

[fccHandler]

Just a comment: About 95% of the music videos I see in the U.S. have obvious 3:2 pulldown patterns, but the patterns tend to shift at scene changes, suggesting that the segments are shot on film and then edited together after being put through the telecine process. It's almost impossible to perfectly recover the original progressive film source from these (Decomb does the best job I've seen).

@Swan:
I too have seen PAL videos which have been converted to NTSC by blending the fields. I hate it, because it's impossible to recover the original source after this butchery. :(

I'm not exactly sure what you mean by phase-shifted, but I remember once having to fix my capture of a rare progressive video with Avisynth:
AVISource("capture.avi")
SeparateFields()
DuplicateFrame(0)
Weave()
In effect, sliding all of the fields forward by one field eliminated the combing in this particular video. (BTW the video was Patricia Manterola "Que El Ritmo No Pare")

@sidders:
My advice is the same as Swan's. If you're going to DVD, don't deinterlace.

[bb]

You've read my advice already, and it differs from Swan and fccHandler in a single point: if your video is phase-shifted (you can test with fccHandler's script and see if some combing artefacts remain), then it's better to reconstruct the original progressive frame. For this there's no quality loss, and you'll get better compression by encoding progressive MPEG-2. fccHandler's script doesn't work in all cases, e.g. if the phase-shift changes somewhere in the middle of the video. Use Telecide() instead: it adapts to these situations dynamically.

@fccHandler:
phase-shift is exactly what your script removes (provided that it's constant).

bb

[vhelp]

hmm.. here is the US, most Music Video's are Telecined (24fps converted
into 29.970fps) or 3,2 3,2 3,2 as stated above.

Dealing w/ NTSC's Telecined videos is close to 95% accurate when
processed w/ this simple AVS script as bb said..

Telecide(swap=false, post=false, guide=1)
Decimate(cycle=5)

..seems to work for me for most of my MTV video's but it's not 100%
accurate. You'll never achieve a TRUE 100% accurate IVTC process.
ie, when a scene changes, weather its changing during an Interlace
frame or not, the final scene's pattern will most likely broken
(incorrect 3,2 pattern)

CMT (cuntry music television) has a number of Progressive video's
and I did one this evening. Some commercials also have Progressive
frames.

The best one can do is First dicect your video in vdub and notice
the pattern ie, 3,2 3,2 3,2.. would mean your captured video was
processed via Telecine, while a pattern like 1,1,1,1,1,1.. would
mean each frame is Interlaced (I prefere Interlace becuase I do
much better w/ those encodes) These 1,1,1.. patterns are distored
lines (Interlaced)

The thumb is:
-------------
* if 3,2 3,2 3,2.. is noticed, use an IVTC
* if 1,1,1,1.. is noticed, use a good de-Interlace method
* if none, (no distored lines) then use Nothing and encode at 29.970
..for smoothest video. Don't perform any such IVTC or de-Interlace
..on these.

Any dropped frames in your capture, will cause corrupt IVTC (or
non video smoothness, ghosting etc) during play.

-vhelp