Default of "De-Interlace" settings in Vegas.

Liam_Vegas wrote on 7/13/2005, 11:31 AM
After all these years of editing with Vegas... the default project settings for "de-interlace" has just hit me... and I have a sinking feeling that I may have been producing lower quality output as a result.

The issue is this. When you start a new project.. .it seems the default for project properties is set to "de-interlace" of Blend Fields.

My thought all this time was that if I am not rendering to progressive formats then this setting would be irrelevant... as a simple render to an interlaced format would not do any de-interlacing. WRONG!!!

I just rendered a project where I "letterboxed" the footage. The destination was DVD so I was rendering to MPEG2. Thus... although my external previewing was showing no problem... after rendering to MPEG and playing out to the TV... I thought I noticed it was a little softer than how it looked while previewing from the timeline.

I decided to render to AVI and load that into the project above all the "real" tracks and then mute/unmute the track so I could compare frame-by-frame with the original.

Sure enough... there is a significant difference between the rendered/unrendered video.

I racked my brains trying to figure out what was going on... and then decided to mess with the de-interlace settings. I set it to none. Rendered to AVI again and repeated the comparison process. Sure enough.. the3 video this time was perfect and I could see no difference between the pre-rendered/rendered video.

So... now I'll be sure to set my de-interlace settings to NONE on every project from now on.

Question is though.... under what circumstances would setting the de-interlace method to none - start to cause me trouble?

Now I feel - with this personal revelation - that I really don't understand how this de-interlace property factors in to the way the project renders.

Can anyone take a stab at explaining this to me?

How do you all setup your project properties as far as de-interlacing?

Comments

Spot|DSE wrote on 7/13/2005, 11:54 AM
First question is how you letterboxed. Pan-crop? Track Motion? mask? Project settings change? Because all of fhese will affect a field. While I've never considered this as a potential red flag, I've just rendered a 10 second "Indian Head" test pattern with a gradient laid vertically. Renderd in Vegas 5 and 6, rendered with both settings, and only see a difference when I apply pan/crop or track motion to create a letterbox. Using a mask didn't reduce quality at all.
Liam_Vegas wrote on 7/13/2005, 11:57 AM
Yeah... I think you hit the nail on the head. In this case I set pan/crop on each event to the widescreen pre-set.

Still... it seems odd to me that doing that will cause a de-interlacing of the video.

Just something to watch out for I guess.
Coursedesign wrote on 7/13/2005, 12:21 PM
I wonder if Vegas deinterlaces before doing the pan/crop or track motion, and then reinterlaces afterwards?

Not as crazy as it sounds, this is standard for much post work.

I'm suffering with this while developing a new "visual language" for video training. A lot of post work requires progressive frames to work best or at all.

My next camera will have to be progressive, this interlacing anachronism is creating a lot of extra work.

Does anyone know for sure if Sony's "24PsF" is really progressive?

The qualifier "sF" makes it sound like weasel wording for "kinda progressive", somewhat like "frame mode".

I know it stands for "segmented Frames", but are these really a single frame captured progressively and written to a 1940s interlaced TV format as two fields?

Liam_Vegas wrote on 7/13/2005, 12:55 PM
So.... if Vegas needs to de-interlace if you use certain FX''s... my question is then what will happen if I set the project properties for de-interlace to NONE?

I can obviously do some tests... but it would be very nice to have the "straight-poop" on what the full effect of this setting will have.

As for that 24PsF for the Sony HDV camcorders... my understanding is that it is not true progressive... it is doing something in-camera to simulate progressive. I don't have anything to add as far as what this means to the whole debate on real-progressive vs this "fake" progressive. There were LOTS of discussions about this when the cameras first came out.. both here and on other forums dedicated to HDV.
Laurence wrote on 7/13/2005, 1:20 PM
Be careful before you turn the deinterlace settings off!

The deinterlace setting is really important if you are resizing interlaced video in any way, including changing the aspect ratio of 4:3 interlaced video to 16:9 or vice versa.

For instance, if you have a 4:3 project and you change the aspect ratio to 16:9, if the deinterlace is set to either "blend fields" or "interpolate", Vegas will crop the top and bottom of the image and stretch the image vertically, and as it does this Vegas will separate the even and odd line fields, resize them separately and fold these two resized fields into a correctly interlaced 16:9 moving image.
If you set the deinterlace method to off, what will happen instead is that the interlaced comb pattern will be resized and no longer match the playback of an interlaced television. This won't be that noticable on your computer monitor, but it will look absolutely awful on playback on a typical NTSC or PAL TV.

This awful looking resizing of the interlace comb pattern will happen every time you do any process that involves resizing interlaced footage regardless of how you do it. For instance, if you use Celluloid or Ulltimate S to change the aspect ratio, but have turned off the deinterlace feature, the resulting 16:9 footage will look awful with wavy vertical lines on interlaced playback. If you downres Interlaced HD to interlaced SD with the deinterlace turned off, the same thing. If you render PAL from interlaced NTSC, the same awful wavy vertical lines, etc. The same thing will happen if you zoom in on interlaced footage.

Interlaced video will still be interlaced after the aspect ratio change by the way. That is why I didn't realize this setting's importance on aspect ratio changes and other transformations that are dependant upon a resize. I have also found no noticable difference in the quality of 4:3 to 16:9 converted footage from using the "interpolate" rather than "blend fields for these kinds of changes. As long as the deinterlace is turned on it will work just fine.

When I first ran into this, I had no idea that I had caused the problem myself and reported it as a bug on both this forum and directly to Sony. I thought that this setting was unimportant if I wasn't deinterlacing video and that turning it off would disable one more thing that might be hurting the video quality.

I am not sure how the deinterlace settings affect a 24p render from 60i source material.
VOGuy wrote on 7/13/2005, 1:58 PM
Two issues, in this thread - both related to the De-Interlace issues.

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(1) The "New" project settings include a deinterlace setting. Selecting one option or another does not seem to be translated to the project settings, and you have to go back to "File/Properties" to set it to whatever you want, before saving the project.

(2) Deinterlace is barely mentioned in the "help" system. So far as I can tell, for some types of work it needs to be on, otherwise everything looks like garbage. For others, it needs to be off, otherwise everything looks like garbage. It would be nice if there was some further explanation, somewhere.


(3) If I'm working with footage from my FX1 HDV camera, there are two simple rules for working in Vegas. (A) Deinterlace can't be sent to "none", (B) Set the rest of the "Project "roperties" to match the output from the camera. Deinterlace set to "none" produces video which looks awful, set to "Blend Fields" or "Interpolate Fields" produces video which looks spectacuar.


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Sony's Cineframe 24 mode results in video which looks really good SO LONG AS YOU DON'T CONVERT TO ANOTHER FRAME RATE!. It is NOT 24 frame, but simply an amazing illusion. My little HD project production notes ( http://www.sonymediasoftware.com/forums/ShowMessage.asp?ForumID=4&MessageID=398806 ) Covers this in some detail.

If you want GREAT looking 24fps, shoot at 60i, load it into Vegas with the project settings set to match the Camera's 60i output. (Cineform Intermediate 60i), and make sure that deinterlace is set to "Blend Fields". Then render to 24. Samples of this approach may be viewed at www.hd-tv.us/edit under "Rendering Notes".

According to info on the Cienform site, capturing to Ceneframe 25 (not Cineframe 24), if you have the Z1, will output video which can be used for true 24 fps work. Sadly, If you have the FX1, you can't do that.

Geez this stuff is complicated....

-Travis

Coursedesign wrote on 7/13/2005, 2:30 PM
As for that 24PsF for the Sony HDV camcorders.

Sony doesn't claim 24PsF for its HDV cameras, this is only for their really expensive gear.

My guess would be that it's the real thing, but there is no way to know for sure as long as they use what looks like "weasel wording".

They could just say "24P", but perhaps the qualifier is a way for their crusty TV engineers to try to claim that progressive is something really abnormal?
Liam_Vegas wrote on 7/13/2005, 3:07 PM
Sony doesn't claim 24PsF for its HDV cameras, this is only for their really expensive gear.

Sorry... misunderstood... thought you were talking about the Z1/FX etc.
Liam_Vegas wrote on 7/13/2005, 3:15 PM
The deinterlace setting is really important if you are resizing interlaced video in any way, including changing the aspect ratio of 4:3 interlaced video to 16:9 or vice versa.

Yeah... this is the sort of thing I was worried about. this could give me nightmares. The result of leaving "de-interlace" switch on in this particular project was totally awful for the final render. That's why I turned de-interlacing off.

Luckily in this project I did no re-sizing of the video (track/motion or PIP) so I guess I was not hit by the problem you descibed. However... on many projects I will do such effects. My worry now is that as this is a project-wide property... I'll now need to make doubly sure that I segment the project into seperate vegs where I need de-interlazing to be in effect etc. I also wonder how nested vegs deal with this. If you have a nested veg with de-interlace NONE inside another Veg with Deinterlace ON... does it get messed up?

This just gives me the shivers thinking how complicated it could end up being.

Am I looking at this problem from the wrong angle or something. This is really bothering me.