Interlacing question(s) during capture

[Steeleye]

I have converted 36 two-hour Hi-8 tapes of home video to 72 one-hour mini-DV tapes by playing back the source with a Sony CCD-TR940 camcorder (TBC on) and capturing via S-video cable with a Canon Elura 70 camcorder. I am now in the process of transferring the DV files to an external hard drive using WinDV for archiving and as source material for eventual conversion to MPEG2 for DVD authoring.

When playing back the files on my desktop using VLC or WMP, I notice the expected interlacing artifact. My questions are:
1. What happens to the original interlacing of the lower resolution Hi-8 tape (420 horizontal lines), or VHS (240 lines) for that matter, when converted to DV (480 lines).
2. Should the MPEG2 encoding be interlaced or noninterlaced for playback on modern plasma or LCD displays.
3. Is deinterlaced the same thing as noninterlaced.
4. What is the best MPEG2 encoding tool for converting DV for DVD authoring (I currently have Ojosoft Total Video Converter) and the best deinterlacing algorithm. I have converted with this program using both interlaced and deinterlaced options (not sure of the deinterlacing algorithm used) and see obvious interlacing artifact with the former.

BTW, I previously converted quite a number of betamax tapes, and am currently working on VHS tapes, of old movies and shows to DVD by using an external TBC, ATI All-In-Wonder PCI card and ATI MMC software, capturing MPEG2 on the fly in 1/2DVD format and encoding interlaced (as recommended on this forum). And I don't remember ever seeing the interlacing artifact during frame-by-frame editing with VideoReDoPlus prior to DVD authoring.

Thanks in advance for any assistance in this project that I only want to do once!

[jagabo]

1. What happens to the original interlacing of the lower resolution Hi-8 tape (420 vertical lines), or VHS (240 lines) for that matter, when converted to DV (480 lines).

Vertical lines are used to measure horizontal resolution. That has nothing to do with interlacing. When interlaced video is deinterlaced vertical resolution (measured with horizontal lines) and temporal resolution may be lost.

2. Should the MPEG2 encoding be interlaced or noninterlaced for playback on modern plasma or LCD displays.

Depends. Is it live action video or movies (film based material)? Film based material should be inverse telecined. If you're going to upload to Youtube or some other video streaming service you'll want to deinterlace. For DVD it's generally best left interlaced (except for the aforementioned film based material).

3. Is deinterlaced the same thing as noninterlaced.

No. Deinterlacing is the process of converting two half-pictures into a single whole picture (or two whole picture in the case of "bob" deinterlacers). It produces a noninterlaced frames but they won't be as good as starting with non interlaced material in the first place (of course that's not an option for you since your capturing analog interlaced sources).

4. What is the best MPEG2 encoding tool for converting DV for DVD authoring (I currently have Ojosoft Total Media Converter) and the best deinterlacing algorithm.

Genereally, you shouldn't deinterlace going from analog video to DVD. DVD players and all TVs support interlaced material. Deinterlacing is destructive. It will lose some detail and create some artifacts. Although what you see on a progressive TV screen will be deinterlaced by some method, the difference is this: if you deinterlace in software and produce a progressive DVD you will be forever locking in whatever losses and artifacts the deinterlacing produces. If you leave the video interlaced the DVD player or TV will do the deinterlacing during playback. Although the best software deinterlacers (not the program you're using) now may do a better job than your TV now, future players and TVs will have improved deinterlacing. Your deinterlaced videos will not get better with time, but the playback of your interlaced DVDs will.

You virtually never want to deinterlace while capturing. You will get very poor deinteraceling.

[Steeleye]

Sorry, I meant horizontal lines (vertical resolution)... Still what happens to the original interlaced fields in the lower resolution hi-8 or VHS signal when converted to the higher resolution interlaced DV signal? Do I end up with a complex mix of interlacing at the two resolutions?

[jagabo]

Sorry, I meant horizontal lines (vertical resolution)... Still what happens to the original interlaced fields in the lower resolution hi-8 or VHS signal when converted to the higher resolution interlaced DV signal? Do I end up with a complex mix of interlacing at the two resolutions?

All analog NTSC video has the same number of horizontal scan lines, 485 in the active picture region (525 including vertical retrace intervals). Modern digital devices all capture (or create) 480 of those scanlines.

VHS and Hi8 have lower horizontal resolution than DV. That just means the analog signal is sampled more times along the horizontal axis than necessary. 360 samples along the width may be adequate to capture all the detail stored on VHS tape -- but it doesn't hurt to capture more.

Also note that video engineers quote horizontal resolution over a width of the frame equal to the height of the frame. For NTSC video that's only 3/4 of the width of the frame. So "240 lines of horizontal resolution" equates to 320 lines across the entire width of the frame. 420 means 560 across the entire frame.

[Steeleye]

Thank you for the great replies!

Getting to the final point in my original post, I am still not clear on why I never saw interlacing artifact when viewing/editing the MPEGs captured on the fly and encoded interlaced with ATI MMC from my videotape sources, or captured directly from broadcasts on the TV tuner card, but see them big time on the MPEGs converted from DV with Total Video Converter unless done so without interlacing. Also, if you encode without interlacing (or deinterlace) on a source that was originally of lower vertical resolution like VHS, are you losing that much video quality?

[sanlyn]

Because MMC didn't re-encode your captures. DV to MPEG is two successive encodes. What does that tell you about Total Video Converter and lossy re-encoding?

[jagabo]

I am still not clear on why I never saw interlacing artifact when viewing/editing the MPEGs captured on the fly and encoded interlaced with ATI MMC

Maybe the capture device was deinterlacing on the fly. Or the player was always deinterlacing on the fly.

but see them big time on the MPEGs converted from DV with Total Video Converter

It's possible the program isn't handling the interlaced video correctly. You should post a small sample of the MPG file -- with moderate detail and motion. The source DV of that same section would be useful too.

Also, if you encode without interlacing (or deinterlace) on a source that was originally of lower vertical resolution like VHS, are you losing that much video quality?

VHS does not have lower vertical resolution. It has the exact same 480 scan lines as your DV capture and your final MPG video (if properly converted).

[Steeleye]

Another question re the TBC in the Sony Hi-8 camcorder above. I read somewhere that this is only a line TBC. Should I have also run the video through a full-frame TBC? I do have a Datavideo TBC-1000. Please say no, since I have already done the work and would hate to have to repeat it!

[juhok]

If your captured video is OK without framedrops etc then you have no reason to use Framesync (TBC1000). It will only deteriorate the signal quality with no added benefit.

[Steeleye]

Thanks for your reply! I don't know how to tell whether there are any frame drops going from one camcorder to the other via S-video. I haven't noticed any av sync problems so far but have not sampled too much of the product.

[jagabo]

I don't know how to tell whether there are any frame drops

You will lose sync between audio and video, or you will see jerks in the video.

[2Bdecided]

I don't know how to tell whether there are any frame drops

You will lose sync between audio and video, or you will see jerks in the video.

There are plenty of videos on YouTube that are full of jerks, but I don't think a TBC would have avoided this


Steeleye: make a DVD and watch it on a TV before going any further. You'll see soon enough whether the DVD retains the quality of the originals, or wrecks it.

Compare on a CRT TV if you still have access to one. Some modern TVs can't cope with VHS properly (though DV will be OK), and some will hide certain faults on DVDs (e.g. motion interpolation to hide bad deinterlacing and sometimes even dropped frames) which is why I suggest using a CRT for the comparison if you have one. You'll be able to see what both the source and the DVD really look like and decide whether the result is good enough. Try the DVD on a modern TV too to see how well it upscales.

Cheers,
David.

P.S. VideoReDoPlus (and lots of decent editing programs) deinterlace on-the-fly just for the preview window.