DVD subtitle resolution doubts

[vm123]

DVD supports subpictures upto 720x480/576 size. My questions are
1. Does it support subpicture with MPEG1
2. Does it always put the subpicture with the same resolution as video resolution.
Can a subpicture be 720x480 for video of 352x288. Is it a possible case.

Can anybody please help.

-Venki

[mats.hogberg]

AFAIK, the subpicture should have the same res (max) as the video.
1) You can have mpg1 video with subpictures, yes.
2) I don't think there's any "automatic resolution matching", but as the video and subpicture is in the same wrapper, the question seems a little odd. What do you mean by "it" in 2?
3) I guess you can, 'cause I by mistake authored a NTSC DVD with PAL sized subpictures. What happened was that the lower part (the subpicture below 480 px) didn't show. SO, I guess you can have 352x288 video with 720x480 subpicture, but only the top left 352x288 of the subpic will be visible. I'd even think this would break the DVD std.

/Mats

[vm123]

Thanks Mats for a quick reply.

"It" there means the DVD specs. So you mean to say, we can have subpictures of bigger size than the video, but breaking DVD standard. Infact, there is no point in having spu bigger than video right?.. My intention here is "does the subpicture need to be resized before being belnded on the video". But if at all, the video and subpicture resolutions are same, there is no need of resizing the subtitles. Please correct me if my understanding is wrong.

-Venki

[mats.hogberg]

I've not investigated this deeply, but my understanding is that the video and subpictures should have the same dimensions.
Like I said, at least on my setup, a too big subpicture didn't get resized to fit the video.
IIRC, you can specify an offset (x,y) for a subpicture, which also speaks against automatic subpicture scaling (if it was automatically scaled, it'd always be positioned at 0,0).

/Mats

[vm123]

Anyway thanks for the insights. What is this IIRC. Sorry if it is well known, coz I am new to any subtitle tools.

-Venki

[mats.hogberg]

IIRC= If I Remember Correctly - Nothing to do with subtitles - more with my short memory span.

/Mats

[GTRBudda]

FWIW, I've done a few subbed DVDs, authored with DvdAuthorGui and/or Muxman, with 352x240 video. When I used sub pics that were the same size as the video, they appeared at the top left corner of the screen at about 1 quarter the expected size. Using 720x480 subpics, they displayed correctly. I can't say for sure if that's DVD spec. Both apps accepted sub pics larger than the video, and Muxman is a stickler for spec, so perhaps it is

[vm123]

Hmm. I got confused. So what could be the correct answer. Is it that players which are differing in functionality of playing back the subtitles. But the DVD spec doesn't specify anything.

[mats.hogberg]

Seems like you'll have to try for yourself, doesn't it?
In my experience, subpictures are just overlayed on the video, and if the subpicture is is bigger than the video, the subpicture is cut off.
In GTRBudda's case, it seems like his player always expect the subpicture to be full D1 size, and is resized to fit the video (or rather - is resized by comparing the video to full D1).

/Mats

[GTRBudda]

Actually, in my case, I probably don't know what the heck I'm doing When I was tackling the same issue, I vagely recall reading somewhere that sub pics don't get resized, only the underlying video (maybe something posted here or on Doom9. It's been months, I can't recall), or maybe that was just my take on it.

To further complicate things, for me anyway , DVDAuthor (or Mplex? Spumux? Not sure which) doesn't seem to read 352x240 video size correctly, it gets labled 704x480 in the IFO (Muxman doesn't have that problem). Once I reset it with IFOEdit, it plays back correctly, with the subs. Makes me wonder if the sub pic's display size is set by the IFO, though I've been too wrapped in other things to look into it.

Edit: Here it is, I didn't halucinate http://forum.doom9.org/showthread.php?s=b93e2a38f105e27c1b4c68df06e79394&p=705140#post705140 The thread was about menu subpics, but I tool it to include subtitles as well.