When to interlace?

[dronon]

Hi, newbie here. I have a couple of progressive AVI files that I'd like to convert to DVD format so I can watch them on my TV. I've successfully done this a couple of times already with TMPGenc - this time, however, the AVI files I want to convert have a smaller resolution than I'm used to. Some are 352 x 240 and others are 512 x 384.

My understanding is that my best choices for the DVD format size is to use one of the following:

720 x 480 pixels MPEG2
704 x 480 pixels MPEG2
352 x 480 pixels MPEG2
352 x 240 pixels MPEG2
352 x 240 pixels MPEG1

And I have a couple of questions that probably reflect my deeper lack of understanding. First, if I want to watch DVDs on my TV, do they always have to be interlaced, or is it the safest bet to interlace them anyway? And can I interlace at 352 x 240 mpeg1/mpeg2, or is this a profoundly bad idea in terms of losing picture quality?

My other question, having to do with the 512 x 384 files - should I expand them to 720 x 480 or shrink them down? I've figured out frameserving from Virtualdub - is it better to re-size them there, or let TMPGenc do the work? I've never been sure whether to set the "source aspect ratio" to "4:3 display" or "1:1 (VGA)". I'm going to have to run at least one of the files through Virtualdub anyway because its brightness and tint are way off in comparison to the other episodes I have. That's not a question; I'm researching that one on my own. (grin)

[Ebobtron]

Are you sure your clips are progressive. NTSC is rarely pure progressive these days. This is important if you are resizing your clips.

[Paulcat]

You can set them as progressive for better picture quality, if your dvd player is 'progressive scan' and your television is progressive then you will have a better quality picture than the rest of us!

If you are unsure if your source is progressive or not, load a clip into tmpgenc and in the SETTINGS, ADVANCED tabs, double click on the DE-INTERLACE option. It will bring up an image of your video, a drop down menu of options and an 'apply filter' checkbox. Uncheck the box, advance your video a frame at a time, if you see lines in the image, it is likely interlaced. Select even field or odd field under 'method' and check the box to apply the filter, if the lines disappear, your video is definitely interlaced. If you are encoding to a progressive file, leave the de-interlacing option active when you are encoding...

As for the image size, I have found it is generally better to go smaller, rather than to try and make something out of nothing! If you want to put the files on DVD, 352x240 mpeg1 will have to be converted to mpeg2, either beforehand by you, or by your authoring software.
Personally I don't know if there is a difference between 352x480 and 720x480 for the same running time on a DVD (eg 4 1 hour tv shows at the same bitrate but different resolutions...) Some expert will have to answer that one!

[mpucoder]

352x240 mpeg-1 is acceptable for DVD, it doesn't need to be converted.

[dronon]

Ebobtron, Paulcat: Aha, there's my newbieness showing through - I thought all AVIs were progressive by nature! But now I have a way to check. (checks) No, none of the ones I'm planning to use are interlaced.

(pulls out DVD player manual) It supports progressive! (pulls out TV manual) ...but my TV doesn't. Considering that I may make gift copies of the DVDs or bring them over to friends' houses to watch, I should probably use the option of interlacing anyway. That way, I'm sure there'll be compatibility regardless of circumstances, even if it means a slight loss of image quality.

Arright! Thanks muchly! Then my remaining question is: is interlacing impossible (or stupid) at 352 x 240, or must it be done at (nnn) x 480?

[Paulcat]

Originally posted by mpucoder
352x240 mpeg-1 is acceptable for DVD, it doesn't need to be converted.
Odd. When I try to make a dvd of five or six video-cd files with tmpgenc dvd author, it takes an hour and a half to process, but with mpeg2 files, it takes no time at all (well, obviously not NO time...but under ten minutes for roughly the same GB), so I assumed...

Dronon: A progressive dvd will play on progressive scan players and non-progressive players on both types of televisions, it's just that if you have BOTH, the picture is better!

[MarcN]

No, no, no... ,you are mixing two things up here. :)

If your source material is progressive, ALWAYS encode it as progressive. All DVD players are able to deal with these files. It’s parts of the DVD specification. The kind of TV set is unimportant (as long as it and the DVD Player support the same TV system, PAL / NTSC).

You can get an ever better looking picture if both DVD Player and TV Set support "Progressive Scan". But that feature has (almost) nothing to do with interlaced or progressive video. It’s a different way of sending the signal to the TV and it works with both kinds of video.

Marc

EDIT: Oops, too late. :rolleyes: