It is one of those under-the hood functions that I don't concern myself with. Doesn't matter what field order you render in Vegas, DVDA gets it right.

I don't think DVDA "assumes" anything. My .mpg files work whether they are upper or lower first.
Whether I render a NTSC DV clip with upper or lower first, DVDA gets it right (just tried it).
I have never seen DVDA get the field order wrong. If it did you would know it right away.

I don't know if DVDA handles Cineform. If you are working with DV-AVI, why not Smart Render to DV-AVI and be done with it?

OK so maybe there's no issue. But I'm just uneasy if I don't understand it. Never thought about it before. I wonder how DVDA does it.

What I did in the current project (I had a tight deadline before any replies happened) was to render from Vegas as 50p so it could take whatever lines it wanted in whatever order! I had 50p media feeding that project in any case. Got the job done and it looked OK on a proper ancient CRT TV.

But the reason for using Cineform in the first place was a project years ago of standard definition where if I saved to DV and also to HuffYuv, I could definitely see a difference, albeit a subtle one. Cineform gave same the quality as HuffYuv but much smaller. So that's why I use it now, for standard def as well as high.

You don't have much control over encoding in DVDA.
I think the reasoning behind the product design [or a common sense guess anyway], is that if you have DVDA, you also have Vegas, so why would you not use Vegas for your encodes in the 1st place, where you can [& should] specify clip, project, & render field orders. Once in DVDA, encoding's going to be upper 1st, as that's the common practice std for DVDs [& to a lesser extent mpg2]. BD was later added on.

Video imported into DVDA then [ideally] shouldn't be (re)encoded, so however you set the original render for the title is how it'll stay. Far as the player/TV goes, field order is irrelevant, as either *dumb* device just does what it's told. If/when there's a field order problem it's because the video file was encoded with it screwed up, & either will dutifully play it screwed up too. You can play std DV or a DVD on a regular TV just fine, & they have opposite field orders.

>"...render from Vegas as 50p so it could take whatever lines it wanted in
>whatever order..."

Creating the field order is a function of whatever created the interlaced video to begin with -- everything after that should normally be set to preserve it... if/when software makes a field order assumption that's not because the software knows what it is, but a convenience, saving you the time of setting it if/when it gets it right. The only way to tell the field order of interlaced video of unknown origin is to look at it field by field, preferably during a high motion sequence.

>"...using Cineform... saved to DV and also to HuffYuv, I could definitely see a
>difference, albeit a subtle one. Cineform gave same the quality as HuffYuv
>but much smaller."

There's quite a lot of info on-line RE: codecs & how they work. HUFFYUV was originally designed to be a very fast, lossless codec for analog video capture only -- not display, nor distribution -- & is still used that way &/or as an intermediate format before final rendering. At any rate, reasons for choosing a codec include speed of encoding/decoding, the amount of quality loss (if any), the amount of quality lost converting stored color data from your source format, & lastly the file sizes it produces. I'm not saying use or don't use Cineform, but if you're interested do the research &/or trials to determine if/when it's the best for your work.