Why do my homemade menus look "shimmery?"

[absinthe]

I've been wondering why most of my homemade menus have a certain degree of "shimmer" on TV screens, some more than others. I've noticed this to be true of a variety of menu sources (whether made from scratch in Photoshop or just a simple image imported into an authoring program) and from a variety of authoring tools (DVD Lab, TMPGEnc DVD Author, dvdauthor, Muxman).

You of course don't see this effect in professional or retail DVD menus, and I'm wondering how I can eliminate it. I feel like it has to do with one of or a combination of: 1) colorspace issues, 2) interlacing, 3) pixel shape.

My latest menu, for instance, is a motion menu made using dvdauthor GUI's generated script with my own modifications. I made a 720x480 BMP in Photoshop of a solid color and blending some images into it which I had cut out of the video itself (the video on the DVD). The script creates 6 little video preview windows on top of the background (one per chapter) as well as text for headings and so forth.

Now, the video on this DVD is home-shot DV footage (i.e. interlaced). The little preview windows are very small and I encoded the menu as interlaced. But I just don't think that's the issue. In the past, even still menus seem to have this issue. Text seems especially problematic. There's usually shimmering around text, even in still menus. Is this is an NTSC color issue?

Just wondering how I can get some better results. :)

-abs

[JeremyIrons]

I'm running into the same problems, though I've only been using stills for my menus.

I've narrowed it down to the mpeg2 encoding of the still. I tried encoding at 9000 Kbit/s with mpeg2enc, ffmpeg, and tmpgenc and they all generate that mosquito'ing (artifacts) especially around text on solid backgrounds.

I even upped the bitrate to 15000 Kbit/s for kicks, and though it improved the quality, the artifacts were still visible.

However, if you overlay your text onto a photo for example, the artifacts will usually blend with all the different colors and won't be visible to the naked eye.

Now here's what I don't understand: Creating my DVD menu using dvdauthor results in a poor quality menu m2v file, however creating this same DVD menu in Spruce's DVD authoring software generates a crystal clear menu.

This leads me to believe that you can use your still as-is in your DVD menu (avoiding the lossy compression of mpeg2)... Is this true? Does the DVD spec allow for JPEG's (or other still format) to be used as menus?

[absinthe]

Well I've done some Googling and have found what seems to be an explanation as well as some ideas on fixing it.

Apparently "flicker" is related to playback on an interlaced viewing device (i.e., a TV :)) and is a result of thin (usually 1 pixel) horizontal lines. Also of note, the "aliasing" effect around text causes this as well since the aliasing produces 1-pixel "steps" in its attempt to create a "rounded" look. So that explains the text flicker.

So, what to do about it. Advice I've found so far is

1. Always antialias everything in your menu !!!.

2. Avoid thin horizontal lines. One piece of advice I read was to make them at least 3 pixels, and yet another article advised making the number of pixels even (i.e., at least 4).

3. In Photoshop, when you're done, apply about 0.5 to 1 of gaussian blur to the whole menu. That should take care of any sharp edges in your background.

Also keep in mind that even though some of these steps might make your menu look less than desirable on a computer, it will improve its look on a TV, which is where it matters.

Now, the script created by dvdauthorGUI of course puts text on the menu which I'm guessing is NOT antialiased. I think what I'm going to try is to create the menu script as usual, then open it in a player and take a snapshot. I'll open that snapshot in Photostop to use as a guide for where I want to put text and so forth on my background, antialias and save, and then delete the text in the script.

We'll see how it works :)

-abs

[SomeJoe]

For some other rules on reducing line twitter and crawlies, see my post in this (http://forum.doom9.org/showthread.php?t=66624) thread.

[DaRat]

3. In Photoshop, when you're done, apply about 0.5 to 1 of gaussian blur to the whole menu. That should take care of any sharp edges in your background.

This is actualy not a good solution because it requires you to flatten the image (each time before bluring and saving), instead give text a 1px 50% opacity outer glow (same color as text, if it has texture then you have to rasterize and motion blur it), use vertical 1px motion blur on normal elements with sharp horizontal edges and first of all choose your font wisely.

[absinthe]

This is actualy not a good solution because it requires you to flatten the image (each time before bluring and saving), instead give text a 1px 50% opacity outer glow (same color as text, if it has texture then you have to rasterize and motion blur it), use vertical 1px motion blur on normal elements with sharp horizontal edges and first of all choose your font wisely.
Thanks. I generally take all the Photoshop advice I can get :). Though what I've been doing is saving my file as a PSD before I flatten the image. That way, I can always go back and make more changes. I'll try your method too, though.

By the way, my menu came out much improved following the above steps. However, the little 2-pixel border the the script generated by dvdauthorGUI puts around each video preview boxes is a flickery mess. Even when I enlarge it in size to 4 pixels there's still visible flicker. If I eliminate the borders altogether, then there's flickering from the sharp border of the video. Kind of a bummer. Wish there was some way to overlay a frame.

By the way, can you recommend a font? A few fonts, even? I always have a terrible time choosing. I like Verdana, Trebuchet, and a few others.

-abs

[DaRat]

The problem with flattening comes when you are pushed hard by time issues and/or ppl to finish your job, you _will_ save your flattened image once. :D Regarding fonts I can't really say anything, whatever fits your project. ;)

[FlimsyFeet]

See also:
NTSC Overheat - Safe Colors (http://www.mediachance.com/dvdlab/Help/ntsc.htm)