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flyingrat · 2010-10-05, 15:34

Hello!

I've sometimes noticed difference regarding subtitles for quite some time now (like years really...) but never understood why.

Can someone please explain why the subtitle font and position sometimes differ between different dvd films. When you play a film, the subtitle sometime looks "hard coded" without adjusting to the font settings and the calibrated position.

I haven't had time to dig into the source code so please bear with me..

Thanks in advance!

**CrystalP** · 2010-10-05, 19:38

That's how DVD subs work. They're just a bitmap, overlaid on top of the video. So whatever font and position was used by the studio when creating these images is what you get on your screen.
They look quite blocky on 1080p big screens. Bluray has an improved version of that.

flyingrat · 2010-10-05, 22:39

CrystalP Wrote:That's how DVD subs work. They're just a bitmap, overlaid on top of the video. So whatever font and position was used by the studio when creating these images is what you get on your screen.
They look quite blocky on 1080p big screens. Bluray has an improved version of that.

Thanks for the input!

So in theory one could add a function to resize the bitmap if desired. But changing the position of the bit map shouldn't be problem with the existing functionality. I wonder why the current implementation does make use of the subtitle position settings (set within the calibration menu). Is this by design or could it be a bug?

**CrystalP** · 2010-10-06, 02:00

Sure they can be resized to a different size than a full frame and moved, but I don't know why you would want to do that. Some subtitles are meant to display at a specific position (below the person who's speaking for example, or at the top) and resizing them or moving them will break that.

The position setting of xbmc is for external subs (*.srt for example). They're quite different beasts, and the format doesn't dictate a specific position.

flyingrat · 2010-10-06, 22:52

As you remarked, subtitles do look terrible on a 55" big screen! Thats why I'm trying to figure out if there is a way to enhance the subtitle display engine (if possible)

But I still want to have the possibility to reposition the subtitle bitmap even though there are some special cases that needs to be considered as you mentioned... Nod

Cheers!

**CrystalP** · (This post was last modified: 2010-10-07, 01:50 by CrystalP.)

Well xbmc is open source so you can do whatever you want. It's just not likely to be merged with the main source code if it breaks something.

edit: actually if you're a programmer and want to help, there are better scaling algorithms out there that could help make DVD subs look a better by removing the jaggies. They're scaled with a simple linear algorithm at the moment.

flyingrat · (This post was last modified: 2010-10-07, 19:34 by flyingrat.)

CrystalP Wrote:Well xbmc is open source so you can do whatever you want. It's just not likely to be merged with the main source code if it breaks something.

edit: actually if you're a programmer and want to help, there are better scaling algorithms out there that could help make DVD subs look a better by removing the jaggies. They're scaled with a simple linear algorithm at the moment.

I'm actually browsing "trunk/xbmc/cores/dvdplayer/DVDSubtitles" right now in order to map the member usage, etc. If I can get a good understanding of the structure and all the dependences I'll try to make some experimental changes. Let's see what that will take us...