Subtitles problem with DVB-T, projectX and GFD

[gabier]

Hello,
I processed a DVB-T stream with subtitles with ProjectX, then GFD, but I have problems to get correct subtitles.
The subtitles are displayed, but they are hardly readable, mainly because they are black in dark scenes. Sometimes one or 2 are white, then it goes back to black.
The demux comes with a .SUP and a .SUP.IFO file, so I inserted the IFO in the "special colors" of GFD (it warned me that there could be conversion problems)(??). I tried also a palette suggested by Borax in the thread https://forum.videohelp.com/viewtopic.php?t=319821, but the result was not much better.
I do not know if that comes from the original TS stream or from the processing by GFD, because I have not seen the subtitles when recording, and I have no software player which can play back raw TS streams or elemental streams with subtitles.
I can just forget it until the next recordings and look this time at the subtitles when receiving the DVB-T, but maybe I could try to understand what is going on with the subtitles' colors.
Maybe somebody could give me a link to a doc which explains how it works. Is each subtitle image endowed with 4 figures giving the proportion of the 4 colours of the palette ? Is it possible to give a palette to make all subtitles white, or yellow ?

Gabier

[gabier]

I post this answer to move up the post in the list, as it was in the wrong forum for several days, and also because I have new informations about the problem.
I managed (thanks to manono) to converse my sup files to .Son files, andthus I could be able to load them in DVDLab. And there the subtitles are not black at all, they are white or yellow according to the color specified in DVDLab (these 2 colors are the only possible choices).
They are more readable, but they not very good either, because they are too tranparent.

The way the subtitles colors and other properties are set in authoring softwares is an unfathomable mystery.

Gab

[borax]

You can 'preview' the SUP file in my SUPViewer program. You can also load/manipulate and save the palette there. Maybe it helps.

To change transparency you can edit the alpha values with dvdsubedit on the final DVD structure (vob files from dvdlab). If the palette doesn't fit exactly to the SUP file, you will always get 'strange' results. My 'suggested' palette is ONLY suitable for SUP files created with txt2sup in the 'no ifo file mode'.
Technically each single subtitle can use 4 colors (one of them is always full transparent - so just three remain with variable transparency) from a palette of 16 colors. Therefore one subtitle can use colors 1,3,5,7 the next 1,2,4,6...
I have no idea what your DVB stream contains.

[gabier]

You can 'preview' the SUP file in my SUPViewer program. You can also load/manipulate and save the palette there. Maybe it helps.

Your SupViewer program is very pleasant. Of course, it answers to some questions and raises others.
I think I understand now how the color of each subtitle is set. For instance : from the palette take colors 0, 3, 5, 12 with opacities 0, 4,D,D (hex values). Hence the importance of the palette.
Now, in the TS stream, the palette seems to be in the .SUP.IFO substream and not in the .SUP file. Correct ? Thus if a program uses only the .SUP file, it can only use a default palette with unpredictable results. Still correct ?
Now, concerning my test files, probably the subtitles colors are horrible from the beginning. However, in order to be able in other tests to track the palettes correctly along the processing chain, I would like to understand the details.

If with SupViewer I store the palette of my .IFO file I get the attached file. If I open the file with the Notepad, the first line is 1A79AB. Is that the first color of the palette ? Is it given in RGB codes ? Yet in SupViewer if I click the first color of the palette on the top of the panel I get a colour with RGB (0,0,97) which is in hex (0,0,61). ???

Last I displayed the subtitles with DVDSubEdit in the authored DVD (with GFD) and the subpics look strange (black with white left edge). I also opened the DVD with PGCEdit. It gives a 16 color "SubPicture Color Lookup Table" which looks very much like a palette, and it does not look at all like the original palette. What does GFD with the palette ?
Should I import in the final DVD the original IFO palette as stored by SupViewer ? How ?

Gab



palette_ifo.pal

[borax]

from the palette take colors 0, 3, 5, 12 with opacities 0, 4,D,D (hex values). Hence the importance of the palette.
Now, in the TS stream, the palette seems to be in the .SUP.IFO substream and not in the .SUP file. Correct ? Thus if a program uses only the .SUP file, it can only use a default palette with unpredictable results. Still correct ?

All correct.

If with SupViewer I store the palette of my .IFO file I get the attached file. If I open the file with the Notepad, the first line is 1A79AB.

This is a 'dvdauthor format' where the colors are stored in the YCrCb colorspace (the same way they are stored in the ifo files as you can see with ifoedit). My Subviewer (and also GFD) can translate this values to the RGB colorspace for viewing/editing purposes. The translation is not 100% lossless (therefore you get a warning in GFD).
Concerning the 'final' DVD:
If you import/use the same palette in GfD as you have used in the SupViewer, the result should be the same everywhere: SupViewer, DVDSubEdit, softplayer, stand alone player... (if not, there's a bug!)
I have just made a test myself (with both engines: dvdauthor and MuxMan) and the palette shown in pgcedit is exactly the same. Make sure you have opened the 'SubPicture Color Lookup Table' for the movie (VTST) and not a menu, as the palette for a menu may be completely different. GfD does nothing with the palette except converting colorspaces (RGB<->YCrCb) which is necessary due to the used tools (sup2png+spumux or MuxMan).

[gabier]

Concerning the 'final' DVD:
If you import/use the same palette in GfD as you have used in the SupViewer, the result should be the same everywhere: SupViewer, DVDSubEdit, softplayer, stand alone player... (if not, there's a bug!)
I have just made a test myself (with both engines: dvdauthor and MuxMan) and the palette shown in pgcedit is exactly the same. Make sure you have opened the 'SubPicture Color Lookup Table' for the movie (VTST) and not a menu, as the palette for a menu may be completely different. GfD does nothing with the palette except converting colorspaces (RGB<->YCrCb) which is necessary due to the used tools (sup2png+spumux or MuxMan).

yes, probably I opened the wrong palette in PGCEdit.
I do not know how to get the reason why the subtitles are black where they should be yellow or white. I recorded another movie, and it looks the same. From ProjectX I output Sup and Son files. If I look at the SUP file with your SupViewer, the subtitles are black (or transparent grey). If I open the bmps of the Son files, they are yellow. If I import the Sup file in GFD, I get black subtitles. If I import the son files into DVDLab, it compiles the subtitles stream OK, but I do not see any subtitle.
I am realy confused. Could there be something wrong in the DVD-T TS stream (I get those subtitles from only one station, Arte), or in projectX, about those subtitles ?

Gab

[borax]

I do not know how to get the reason why the subtitles are black where they should be yellow or white

I don't know either. As mentioned above I made a test yesterday with a TS file recorded with WinSTB (DVB-S, channel ZDF) and demuxed with ProjectX. I opened the SUP in SupViewer, used the .sup.ifo from ProjectX as palette and get correct colors. I used the same SUP and palette in GfD and have correct colors in the final DVD structure (using both MuxMan and dvdauthor as authoring engine). I can't tell you where your 'wrong' colors come from... But if you open the SUP file in SupViewer, you can change the palette to get 'correct' colors (they should be correct if you use the .sup.ifo from ProjectX). Save the palette in SupViewer and use it in GfD. If the final DVD still shows 'wrong' colors, cut out a small piece of the stream with ProjectX, and post the SUP and .sup.ifo files here (or send them to me by email). Then I will try to track where the error comes in...

[gabier]

If the final DVD still shows 'wrong' colors, cut out a small piece of the stream with ProjectX, and post the SUP and .sup.ifo files here (or send them to me by email). Then I will try to track where the error comes in...

Yes, it is the same. So I e-mail to you the SUP and the .sup.IFO of a little piece, the ProjectX log, and the first bmp of the subtitles (I do not know how to attach several files to this post )

Thanks for spending some time trying to help me!

Gabier

[gabier]

Just for anyone to be able to know the solution of this problem, which was solved thanks to Borax.
In projectX, if you intend to use SUP files for subtitles, do not choose the 16 colours or 256 colours option in the IRD setting of the Subtitles tab of the presettings, but only the 4 colours option. Else ProjectX tries to map a 16 colours palette (or 256) to a 4 colours palette (maximum for SUP files), and does it wrongly.

Good luck !

Gabier