Interlace artifact HDV to SD

R0cky wrote on 8/12/2008, 8:36 PM
I know the HDV to SD subject has been extensively discussed here and I've read every post I can find on it but still don't get what's going on. First, my only preview devices are the monitor and an external LCD TV. I don't have a CRT monitor so what I'm seeing is on the LCD computer monitor or LCD TV.

HDV 60i footage on time line. No FX as of yet. I want to render out as DV 60i widescreen. The footage is of a bike race so there is lots of fast motion. Project properties are the standard 720x480 DV Wide with deinterlace method on interpolate.

When the project properties are changed from HDV60i to DV Wide 720x480 two things happen. The fast motion which looked great on preview (best) now shows ghosting, i.e. it looks like both fields at once and since there is fast motion there is significant movement from one field to the next. The second thing is lots of interlace artifact - combing.

Since both source and output are interlaced I didn't expect the combing and what's up with the ghosting?

thanks all,
Rocky

Comments

Laurence wrote on 8/12/2008, 9:12 PM
It sounds like you don't have a deinterlace method selected. For some reason Vegas needs the "select deinterlace method" tab to be checked though when you are resizing interlaced footage even though it isn't actually deinterlacing.

If you render from interlaced HD to interlaced SD, you wouldn't think that choosing a deinterlace method would be important, but it is. It doesn't matter which one you choose. Interpolate looks exactly the same as blend fields because it isn't actually deinterlacing.

If this tab isn't checked, the image will be resized like it is progressive video and you'll get all sorts of comb and ghosting artifacts.

farss wrote on 8/12/2008, 10:44 PM
The reason is that each field contains only half the image. As far as I know every system that rescales interlaced video has to de-interlace it then rescale it then re-interlace it. Broadcast quality scalers are rather expensive I believe.

Bob.
johnmeyer wrote on 8/12/2008, 10:57 PM
Right-click on the HDV media and check properties. Look at the field order and make sure it is UPPER field first.

Then, when rendering to DVD Widescreen, make sure the field order is LOWER field first.

Also, follow the suggestions in the previous two posts.

Finally, what playback device are you using for your external LCD TV? I would print the DV 60i back to tape, and then playback from my camcorder. Try that with a short section and see if you get good results.
Laurence wrote on 8/12/2008, 11:00 PM
Also, make sure you're using the "best" rendering setting because of the resize.
bsuratt wrote on 8/13/2008, 7:40 AM
I'm experiencing the same sort of thing... a bit of "fuzz" especially on fast moving background objects. Tried both Blend and Interpolate, little change. Field designations are correct. I'm looking at it on an LCD TV via DVD. Not a showstopper but not as clean as a standard DVD. Haven't tried converting to SD from camera during capture.
farss wrote on 8/13/2008, 7:57 AM
The downside to using in camera downscaling to DV is you're loosing a lot of chroma samples. If you're working in PAL the results when your render to mpeg-2 for DVD don't seem to bad, in NTSC it's another matter by all accounts.

I have to admit that I've managed to get acceptable results using Vegas but I'm still left feeling it could be better. Regardless of NLE this is a pretty common issue. Probably the best results would come from using a better de-interlacer such as Twixtor. Being able to abandon interlacing altogether would be the ideal solution but downscaling that for interlaced delivery can be another can of worms and as the best I can shoot is 25p there's another set of issues to consider while shooting.

Bob.
bsuratt wrote on 8/13/2008, 10:39 AM
Thanks Bob

I may give the camera route a try...(I'm in NTSC) but since I need an HD as well as a SD version this would double the workflow!
R0cky wrote on 8/13/2008, 12:05 PM
I think I have already done what everyone has suggested (and the info was in my original post too)

Deinterlace method was interpolate (I get the same artifacts with blend which makes sense since it doesn't really get deinterlaced).

Source (HDV 60i) media is upper field first and vegas detects it that way.

Project properties std NTSC DV 720x480 widescreen and lower field first

Preview mode is Best.

Output to external monitor is over firewire to a Canopus ADVC-300 driving S-video inputs on my LCD TV. I have not printed out to tape or made a DVD yet.

I see the ghosting and interlace artifacts on both the PC monitor and the external LCD TV.

I'll repeat:

1. since both input and output are 60i interlaced, why is there ghosting when down sampling the resolution?

2. why am I getting this terrible artifact? The video is interlaced both source and output. Or is it just because I don't have a truly interlaced display? This does not happen if the project properties are HDV 60i which is still interlaced even using these displays.
Laurence wrote on 8/13/2008, 2:30 PM
I thought you were talking about artifacts in a render. What you're seeing in a preview window is often not an accurate representation of what you're actually getting. I usually preview HDV at half size so that I don't have to worry about the interlace nonsense. Have you messed around with the preview deinterlace settings?
R0cky wrote on 8/13/2008, 2:54 PM
Preview deinterlace settings are different from project properties? new to me. Is it the "Apply deinterlace filter" checkbox on the preview device tab under options-preferences?
Laurence wrote on 8/13/2008, 3:34 PM
> Preview deinterlace settings are different from project properties? new to me. Is it the "Apply deinterlace filter" checkbox on the preview device tab under options-preferences?

Yeah they are. Options / Preferences / Preview Settings.
fldave wrote on 8/13/2008, 6:20 PM
Don't change your project properties to DV. Keep it at native HDV.

You are correct, with deinterlace - interpolate.

Render MPEG2 to Best, DVD Archictect NTSC DV Widescreen, or at a minimum, move the quality slider on the render video tab to 31, best. According to John Meyer, also select "stretch to fill video frame" to fix the minute aspect difference.

Then report back?

Edited: the ghosting may be consistent with the upper/lower field setting. DV should be LFF, so if the above doesn't fix it, switch the HDV from UFF to LFF to see if it makes a difference?
ScorpioProd wrote on 8/13/2008, 10:06 PM
Though the world is LCD, if you can check your finished product on a CRT, you may be surprised. I've had some stuff from HD to SD looking pretty bad in Vegas preview and it looks correct on a true interlaced CRT.
R0cky wrote on 8/14/2008, 8:03 AM
Preview deinterlace filter makes no difference.

I need to burn a dvd and look on a CRT. It is frustrating that the preview cannot seem to give a reasonable interpretation of what's going on with so many things that can be mis-set.

Changing field order in the DV project properties makes no difference upper or lower first. However changing it to progressive gets rid of both the ghosting and the interlace artifacts.

So maybe when I captured (using cineform Neo HDV) I had the deinterlace box checked by mistake and my footage is actually progressive when I think it's 60i/UFF? Easy way to check that? In Vdub maybe? I will recapture some of it to make sure.

Vegas however does think it's 60i/UFF.

thanks all,
Rocky