Thanks musicvid10, - That was my first Option, Line-1
but since this is a techy site selling DVD Authoring software - so I was hoping the latest standards would be forthcoming....
As I mentioned it was the case that DVD preferred -I (interlaced) Media, but that may have changed...

A few years back they were called 25i and 25p. The number meant there were 25 frames per second, while "i" meant each frame was made of two interlaced fields while "p" meant the frame was a single full field.

Somewhere along the line people started calling the interlaced version 50i instead of 25i. I don't understand why or how this happened. To me, 50i means there are 50 frames per second and therefore 100 fields. The problem is that since both "25i" and "50i" have been used to refer to the same thing, and to different things, and now we have confusion.

The same thing has happened in the NTSC world where people now use 60i to refer to 30 frames per second interlaced, when it used to be called 30i. And on top of that, most of the time "30" really means "29.97002997", except for the very rare time it means "30", and there's no way to tell which is meant in some contexts.

DVDs are either 25 frames per second interlaced or 29.97 frames per second interlaced. You can use progressive flagged as interlaced, but the DVD player will treat it as though it was interlaced. It may look sharper on slow moving images, but will look more jerky on fast moving images.

DVDs are always encoded with SD MPEG2. The maximum movie time of a DVD is inversely proportional to the data rate used during encoding. At the max reasonable rate of about 8 Mbps you will get a little over 1 hour. If you encode at 4 Mbps you will get twice the time but poorer quality.

Yes, DVDA can somtimes be a bit pessimistic about how much data will fit on a disc. If you think it should fit, create a DVD folder without burning and check its size. A standard DVD holds about 4,700,000,000 bytes.

You should never create a normal DVD using m2ts (HD MPEG4 AVC) directly but rather render it to SD MPEG2 first with Vegas, and follow the recommendations published here ad nauseum.

AVCHD Discs (HD on standard DVD media) have passed their "use by" date. I suggest you don't go down that track.

Thanks PererDuke, that does help.....
and now a deeper isse has come up:- how can I create a longer-play DVD.
BTW I'm using v5 DVDAS.
If I go into "Properties" I can set [ PAL format ], the normal DVD resolution 720 x 576 - or a very slightly-lower resolution, - 704 x 576.
The BitRate (under Properties.) gives me a slider and unfortunately I can't get back to exactly 8.000 - does this really matter? I've set it to 8.000 by using the Keyboard. Why doesn't the slider offer common-values? - So I conclude it doesn't matter . . . and the Playback machine must be capable of understanding this Bit-rate so it picks up just enough.
To make a playable DVD does the bitrate matter? I accept Quality will vary!. Can I drop it as low as 0.192 which seems excessivly low . . . will any video show? For music files I would be happy with TEXT-only and could accept a moderately poor resolution. There is no "movement" as such . . . just information as to the Piece that's playing, etc.
But, I'd like the DVD-Audio to remain HiFi.
The application of these DVDs is for Music playback. However, I'm keen to learn what the size-limits are for DVD / DVDA Studio. . . . . where a projector is available to show Text....so the listener knows which piece is being played.

CD (off topic)
I realise I can burn a CD ( e.g. using Sound Forge.)... when audio-only is acceptable..... Yet the same Data-Rate issue applies: that CD's seem to be fixed duration of about 1-hr. This 1-hr figure comes from my earlier-burnt CDs.
I appear to be creating FLAC audio-files - although mp3 might be smaller, I don't think I've changed the file-type and I have created CDs that play on domestic CD Hi-Fi players ( and DVD-players that support CD.).
I've read the SF Audio-Bit-Rate Help-file, but It's somewhat too deep for me to attempt changes. What I'd like is a CD that will play for 4-hours, for voice, when music quality is no-longer an issue. For example learning a Script. I'd use the extra time to repeat, to make learning easier...
Thanks...

You might read about making a MUSIC/VIDEO compilation.

To create a longer play DVD you drop the bit rate of the video. 8 Mbps will give you about 1.25 hours. 4 Mbps will give you about 2.5 hours, but at lower quality. You will have more control over your video encoding if you do it in a video editor, such as Vegas, rather than DVD Arch.

If your video is a series of static text slides, you should be able to use a very low bit rate with good quality.

The audio is not affected by what you do to the video.

An audio CD is fixed design: stereo, 44.1 kHz sampling rate, 16 bits per sample. You can put up to 80 minutes on a standard CD-R. That's it.

If you put MP3 or WMA audio files on a data CD, you have much more control, but these files won't always play in CD players. They usually play in car sound systems and DVD players, however.