[Approved] Fix for TV4 Science Fiction no def subtitle language (1 Viewer)

[jblomb]

On TV4 Science Fiction I have noticed that every time I watch the channel I have to manually select subtitle page 890 to display subtitles, although I have selected swe as the default language. I finally decided to look into the problem and here are my findings:

In the logs I noticed:

2010-03-09 10:00:06.290290 [Debug][(10)]: Page 90 is of type 2 and in lang swe
2010-03-09 10:00:06.293290 [Debug][(10)]: Page 91 is of type 2 and in lang nor
2010-03-09 10:00:06.294290 [Debug][(10)]: Page 92 is of type 2 and in lang dan

...but page 90-92 are not valid pages. They are supposed to be 890-892.
Took some time to figure it out..

in TsReader/PmtParser:

int teletext_magazine_number = (b3 & 0x07); // last(lsb) 3 bits

int teletext_page_number = (section.Data[pointer + varBytes*j + 6]);

int real_page_tens  = (teletext_page_number & 0xF0) >> 4;
int real_page_units = teletext_page_number & 0x0F;

int real_page = teletext_magazine_number*100 + real_page_tens*10 + real_page_units;

There you can see that magazine number can be 0-7. BUT in the ETS specification it states that:
"Magazine number 8: A packet with a magazine value of 0 is referred to as belonging to magazine 8."

Add something like if (teletext_magazine_number == 0) teletext_magazine_number=8;
...and it's working again.

log after patch:

2010-03-09 10:40:48.276963 [Debug][(10)]: Page 890 is of type 2 and in lang swe
2010-03-09 10:40:48.278964 [Debug][(10)]: Page 891 is of type 2 and in lang nor
2010-03-09 10:40:48.279964 [Debug][(10)]: Page 892 is of type 2 and in lang dan

Attached is a patch for TsReader.

for a great program!!

 

[jblomb]

Another approach is to leave TsReader alone, and patch Core/Player/TeletextSubtitles/TeletextMagazine.cs instead.

if (page < 100) page += 800;

To me this solution seems safer, but might not solve everything.
It will solve all problems with subtitles mentioned in the first post though.

Regards
Blomman

EDIT: New corrected patchfile

 

[Mr Hipp]

Blomman - have you done any analysis of the impact not updating tsreader.

 

[jblomb]

Nope. I had a hard time figuring out how things are connected, and I KNOW I haven't figured everything out
That's why I thought it might be safer to patch TeletextMagazine.cs instead, but I doubt it would be any problem patching TsReader.