Salton Sea Menu.....how did they do this?

[dan]

Just picked up The Salton Sea DVD. The menus are nothing special, but the chapter selection is really wierd, something that I, though I have limited experience, haven't come across. [Or at least took the time to notice before.]

The chapter selection screens aren't animated, and they have a thumbnail for four chapters on each page. Here's a screen of the menus when none of the buttons are selected.

Unselected (http://pubweb.nwu.edu/~dcf797/SaltonSea/SaltonSeaUnselected.jpg)

Now, when the cursor is moved over a particular thumbnail it goes from, I guess the easiest way to say it is, washed out [like in the previous screenshot] to vibrant colored.

Here's a screen of the menu with the second thumbnail highlighted.

Highlighted (http://pubweb.nwu.edu/~dcf797/SaltonSea/SaltonSeaSelected.jpg)

As you can see, this isn't [well, it doesn't seem to be] a traditional subpicture color change effect, as there are more than four colors in the area that changed. The name of the chapter does seem to be a simple subpicture color change, as it goes from being transparent to yellow though.

This isn't some computer DVD player trick only, as it does the same thing on my Panasonic set-top.

I'm also very sure that it isn't jumping to some new screen that has the thumbnail highlighted, as the change is instantaneous, even in the set-top...this isn't the scientific way to do things, but I can't hear the laser moving to somewhere else on the disc.

I'm posting this here to see if anyone knows how this is done before I spend the time ripping apart the menus and seeing what's what.

Is this some complicated trick or are the highlight images actually somehow a subpicture trick?

Thanks guys.

Dan

[mpucoder]

This isn't all that difficult. They made use of the transparency (or alpha channel) of subpictures. There is no pixel information, that resides in the video underneath. However, if you go looking for it, the CLUT in the ifo does not contain alpha data, that is in the subpicture itself. See the 04 (SET_CONTR) command for subpictures at http://mpucoder.kewlhair.com/DVD/spu.html

You can make a menu like this by using white or black as the unselected color, with some intermediate value of transparency. The selected color doesn't matter, just make it 100% transparent.

[dan]

Thanks a lot. This is why these forums are so great.

Dan

[rubic42]

Yeah, this place is great. I'm subscribed to the DVDList, where the impression I got was that a lot of professional DVD authorers exchange information on this mailing list. But this forum is often times much more helpful. Thanks all.

[auenf]

i remember a thread from ages ago that had a similar thing; when a button was hiligted, it was animated, when it wasnt hilited, it was still, or solid colour. which is a similar thing, setting the subpic fully transparent on hilite, but in 'normal' mode its fully opaque.

Enf...