De-Interlace in Vegas or not??

[Chris Harding]

Hi All

As I'm outputting to SD DVD and my cams only shoot 1920x1080i I need to de-interlace the footage before rendering to a DVD Widescreen file in Vegas 9.

At the moment I'm transcoding the AVCHD clips to M2t and using Upshift to also make the clips progressive. They offer 3 settings "Copy from Input" "Interpolate" and "Progressive"

The end result using progressive looks pretty good but I told that you are losing resolution by doing this and it's better to let Vegas de-interlace using the "interpolate" preset in Project properties. However others say that it's fine to de-interlace before Vegas and you don't lose any resolution!!. I'm confused on how the fields work in HD!!!

Any help or opinions here??? Will I get a better result if I use the Interpolate setting in Upshift or is it best to let Vegas do the job??

Much appreciated

Chris

[Dale Guthormsen]

Chris,

I do not use upshift, however I use Vegas and I use the interpolate setting and i have been pleased with the results. In my opinion Vegas interpolates better than any other software i have personally used.

I would just run a quick check on some action footage and compare.

[Perrone Ford]

If it's for personal use, I let Vegas interpolate. If it's a real job, I deinterlace in Virtualdub. MUCH better results and works quickly, but does complicate the workflow.

[Jim Snow]

When someone makes a decision to convert from HD to SD, they also make the decision to "lose resolution" by definition. Sounds obvious but 1920 X 1080 or 1440 X 1080 is higher resolution than 720 X 480. If you choose to convert interlaced HD video to progressive SD, you don't need to lose any available SD resolution. You already made that decision when yoo decided to DOWN convert. If one field is discarded and the other doubled (to maintain aspect ration) there is NO loss in the available SD resolution. BUT, what you DO lose is the smoothness of motion you had in the source interlaced footage. You may like that "look"; you may even call it "artistic" but with 60i you get 60 "pieces" of motion information per second; with 30P you only get 30 "pieces" of motion information per second. If you want your cake and eat it too, you want 60P not 30P - - - but, minor detail; DVD doesn't support 60P. If you keep both fields that were shot at different moments in time but present them at the same moment in time, you WILL get some blurring as an undesired side effect.

The way to achieve the smoothness of motion provided by 60i HD is to preserve each field when encoding and reduce the number of lines in each field to that required by the target SD resolution and then reinterlace each field after the reduction. The $64K question is; which encoder / procedure does this correctly? There is a HUGE amount of misinformation on this subject.

If motion judder is your thing, that's fine; you can even call it artistic but at the end of the day, judder is jerky motion. You may even like it so much that you name your business Motion Judder Productions. But I don't agree with hitting the technical "wall" and then calling it artistic as a cover or defense. Why not just hack the frame rate down to 10 per second and call it a masterpiece?

[John Cline]

Originally Posted by Jim Snow

The way to achieve the smoothness of motion provided by 60i HD is to preserve each field when encoding and reduce the number of lines in each field to that required by the target SD resolution and then reinterlace each field after the reduction. The $64K question is; which encoder / procedure does this correctly? There is a HUGE amount of misinformation on this subject.

If you select either "Blend" or "Interpolate" as the deinterlace method in the project's properties and select "best" for the rendering quality, Vegas will "unfold" the fields, resize them using a bicubic interpolation algorithm and then refold the "fields" back into a 60 (or 50 PAL) field per second interlaced video. Vegas is doing it exactly how it should be done, it will spatially rescale the video while maintaining all the temporal resolution of the original footage. When resizing, Vegas is not actually blending or interpolating, you just need to have the deinterlace method set to something other than "none."

Also, I agree 100% on your reasons not to convert video to 30p. I wonder how many people don't realize that by converting 60i to 30p that they are throwing away half of the temporal resolution?

[Jim Snow]

Originally Posted by John Cline

I wonder how many people don't realize that by converting 60i to 30p that they are throwing away half of the temporal resolution?

I suspect more don't realize than do. I think they get hung up on some arbitrary notion such as "p is better than i" and that's as far as it goes in their "thinking." This is probably some sort of mutated crossover from "progressive TVs are better than interlaced ones." There is no sense that this is apples and oranges so the end perception is that "p" is better than "i". Simply because the TV is able to display progressive footage doesn't mean it can fix the temporal loss when the footage was originally shot as interlaced but displayed as progressive. Sure, if one could shoot 60P and display 60P that would be good BUT the DVD architecture doesn't support 60P so it's a moot point. Blu-ray is a different story. If one can shoot true 1920 X 1080 60P, they can make a HD 60P blu-ray disc and play it as long as the player and TV support 1920 X 1080 60P. It would look very nice but it doesn't help with the OP's question regarding SD DVD. The DVD spec doesn't support 60P.

[Chris Harding]

Hi Guys

Very much appreciated!!! I was getting very confused with the fields and de-interlacing issues and that clears up a lot of issues where there seemed to differing opinions.
Because I'm using Panasonic AVCHD I also have the facility to use their transcoder and drop the footage directly to SD. To be perfectly honest I very much doubt that any client would question the quality of the footage if it was transcoded directly to SD or went the HDV to SD route, unless they had something to compare it with!!

Chris

[Jim Snow]

Originally Posted by Chris Harding

Because I'm using Panasonic AVCHD I also have the facility to use their transcoder and drop the footage directly to SD. To be perfectly honest I very much doubt that any client would question the quality of the footage if it was transcoded directly to SD or went the HDV to SD route, unless they had something to compare it with!!

Chris

You can always do your own comparison and make a decision based on the results versus the time required for each method.

[Chris Harding]

Hi Jim

Actually, for budget weddings I'm using the AVCHD files transcoded direct to Widescreen AVI..it's faster than transcoding to M2t and the quality difference is very difficult to see even on a 42" HDTV. I did 3 clips on a DVD and invited two friends to watch and "grade" them (AVI, M2T and MTS all to DVD) Even they had problems with saying which was best AND they had something to compare to!!! The bride will firstly be more interested in the content than resolution and secondly she will have nothing to compare to!!!
In fact well lit and composed footage from an AVI could quite easily "look" better than poorly lit footage rendered from HDV!!! AVI will also render to MPEG2 in half the time which can help if you are flooded with work!!!

Wouldn't life be a lot easier if standard DVD players could accept video in all sizes and formats and simply just play them on the TV they are connected to!!!

Thanks again for practical comments ..sometimes we have to say, this is the practical way to go for optimum workflow.

Chris

[John Cline]

Jim Snow: FWIW, Sanyo has two consumer camcorders in the Xacti line that that record full-HD 1920x1080 60P using h.264 at 24Mbps. One is the VPC-HD2000 (~$480) and the other is the VPC-FH1 (~$420). They use a .4" CMOS chip and record to SD-HC cards. I'm going to pick one up to play with it.

[Jim Snow]

Thanks John, Please post back after you try it out and let us know your impressions.

[Robert M Wright]

If you are delivering on standard DVD (DVD video compliant), you don't have the option of delivering 60p (at any spatial resolution).

[Jim Snow]

Originally Posted by Robert M Wright

If you are delivering on standard DVD (DVD video compliant), you don't have the option of delivering 60p (at any spatial resolution).

Quote from my post above:

"Sure, if one could shoot 60P and display 60P that would be good BUT the DVD architecture doesn't support 60P so it's a moot point."