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General troubleshooting
-----------------------
Don't see any subtitles?
1. Do you really have the patch for VDR applied and are you really running
this patched VDR version?
2. Do you have the teletext subtitle option in VDR's setup menu in the DVB
section enabled?
3. Are you sure your broadcaster supports automatic detection of the subtitle
pages? If not, you must manually configure the subtitle pages in the
channels.conf!
4. Are you sure the current broadcasting does have subtitles at all? No
channel sends subtitles 24/7, so please make sure the current broadcasting
really contains subtitles. You may want to check this with the OSDTeletext
plug-in by manually going to the subtitle page.
5. Do you have selected the subtitle languages you want to see in
the plug-ins setup?
Nothing works, want to report a bug?
Please report bugs to:
http://projects.vdr-developer.org/projects/plg-ttxtsubs/issues
...and include the following information:
- VDR version, plug-in version, patch version
- VDR's channels.conf and setup.conf
- Syslog and stderr messages
- If possible the complete patched VDR source tree
- If possible a small 5min-recording which should contain subtitles. You can
use a service like e.g. use a duckload.com to upload this (the bug-tracker
does not allow attachments larger than 5 MB). You should include the delete
link, so we can remove the recording after downloading it.
Advanced troubleshooting
-------------------------
The following describes some more detailed troubleshooting procedures but
is partially deprecated (Especially the references to the ttxtsubs output
on STDERR or the syslog):
Ttxtsubs is made to be fully automatic with no other user settable
settings than preferred subtitling language or languages and a few
appearance options. This is how set top boxes work, and, in my
opinion, how these things should work. Users should not have to know
anything about PIDs, encodings or other strange information as in this
case teletext page numbers.
Sadly, some channels do not provide the information necessary for
automatic subtitle decoders to do it's work, and some do but do it
wrong. There has also been bugs in ttxtsubs that made it incorrectly
parse the information it gets, I of course hope those are gone by now.
If you think there are subtitles on a channel but ttxtsubs doesn't
show them, you may want to read the text below.
Troubleshooting ttxtsubs
------------------------
A good thing to check first is how another set top box behaves. If the
other set top box automatically finds and displays teletext subtitles
while ttxtsubs don't, there is probably a problem in ttxtsubs.
If neither the set top box nor ttxtsubs automatically finds the
subtitles but you can get them by manually entering the teletext page
number for them on your TV set or your DVB decoder, chances are that
the subtitles aren't announced in the channel's "service information",
at least not correctly. You can double check this using dvbsnoop, see
below.
To find the subtitles, a DVB receiver as ttxtsubs scans the channel's
"Service Information". This meta data contains information about what
PIDs to use for receiving the channel, such as what PID to use for
video and what audio PID should be used for what language. VDR 1.3 and
up uses the Service Information for automatic video and audio PID
setup just as a typical set top box does.
For teletext with or without subtitles, the Service Information
contains information about what PID and what teletext page to use for
what language and purpose. A typical set of information for a channel
with Norwegian and Swedish teletext with subtitles could look like
this:
PID Language Teletext Page Purpose
4711 nor 200 Initial page for teletext browsing
4711 nor 299 Subtitles
4711 nor 298 Subtitles for hearing impaired
4711 swe 300 Initial page for teletext browsing
4711 swe 399 Subtitles
4711 swe 398 Subtitles for hearing impaired
In this case, a receiver set up for Norwegian subtitles for hearing
impaired would use PID 4711 and teletext page 298 for subtitles. If
the user pushes the button for interactive teletext information
browsing, the set top box should start with presenting page 200 which
is supposed to be an index page in Norwegian.
Note that the PID may be different for each language and purpose. This
is one reason why ttxtsubs has to find out the PID itself and doesn't
care at all about how you set up the channel's TPid.
To find out what ttxtsubs is doing, you must currently (0.0.5pre2)
look at the stderr output in the shell where you run VDR. In a future
version, it may instead show this in the VDR menus in a more user
friendly manner. At the end of this text you can find some typical
messages from ttxtsubs with explanations.
You can use dvbsnoop, http://dvbsnoop.sourceforge.net, to check what
the service information really says.
First dump pid 0 to find the Program Map PID for your channel:
$ dvbsnoop -n 1 0
and get for example:
Program_number: 5060 (0x13c4)
reserved: 7 (0x07)
Program_map_PID: 5060 (0x13c4)
The entry you are looking for is the one with a Program_number the
same as the Sid number in VDR.
If you don't know the program number, you can dump pid 17 and
look for the channel name you want and get the Service_id number:
$ dvbsnoop -n 1 17
You may need to do this several times to find your channel (or use a
number larger than 1 after -n).
In this case the program map PID is the same as the Program Number.
When you know the program map PID, dump it:
$ dvbsnoop -n 1 5060
and look for
DVB-DescriptorTag: 86 (0x56) [= teletext_descriptor]
Again, you may need to do this several times to find this information
(or use a number larger than 1 after -n).
On a well behaved channel with teletext subtitles you should see
something like this:
...
Elementary_PID: 1024 (0x0400)
...
DVB-DescriptorTag: 86 (0x56) [= teletext_descriptor]
Descriptor_length: 30 (0x1e)
ISO639_language_code: swe
Teletext_type: 1 (0x01) [= initial teletext page]
Teletext_magazine_number: 1 (0x01)
Teletext_page_number: 0 (0x00)
ISO639_language_code: swe
Teletext_type: 2 (0x02) [= teletext subtitle page]
Teletext_magazine_number: 6 (0x06)
Teletext_page_number: 146 (0x92)
ISO639_language_code: swe
Teletext_type: 5 (0x05) [= teletext subtitle page for hearing impaired people]
Teletext_magazine_number: 7 (0x07)
Teletext_page_number: 146 (0x92)
....
This is the information that a DVB decoder uses to find the
subtitles. If you find a DVB-DescriptorTag of 69 (0x45) =
VBI_data_descriptor or 70 (0x46) = VBI_teletext_descriptor that you
think could point out the subtitles, please contact the
author. Ttxtsubs currently doesn't decode those as I have never seen
them, but it is probably easy to implement. If there is no information
for subtitles but there are subtitles in the teletext stream, please
ask the TV company to fix it, see next section.
If you want to watch a channel that has teletext subtitles but the
subtitles aren't announced in the Service Information, contact the TV
company and ask them to correct this. If you politely inform them
about the problem, they may very well correct it. After all, it is in
their interrest to have satisfied viewers. Don't take "you will have
to enter the subtitles page number on your TV set" as an answer - this
is just to sad an user experience and is not how it is supposed to
work with DVB. Try to convince them that this is what you and the
standard and the viewers want. Here is a template for such a letter:
-----
Sirs,
Your TV channel [CHANNEL NAME] that can be found on DVB
[Satellite/Cable network/Terrestrial network] [SATELLITE POS/NETWORK
NAME] with video PID [NNN], audio PID [NNN] and teletext PID [NNN] has
teletext subtitles on page[s] [NNN[, NNN...]]. Sadly, the DVB service
information for your channel does not announce the subtitles, so my
DVB receiver can not find them and display them.
I hereby ask you to update your channel's service information to
also announce the existence of the subtitles. Since your service
information already announce the existence of the teletext PID, only a
small addition is needed to also announce the teletext subtitle
page[s].
For further information about the service information descriptor that
is needed, please see the standard document ETSI EN 300 468, paragraph
6.2.40. You can download this document for free from www.etsi.org.
By sending a teletext subtitles descriptor according to this
specification, my and other decoders that are using it will be able to
automatically pick them up and present the subtitles to the viewer.
-----
Note that some channels don't use teletext subtitles but instead use
DVB subtitles, which is something different. Support for DVB subtitles
is included in VDR >= 1.5.10; you don't need this plugin for them.
Typical ttxtsubs messages and explanations
------------------------------------------
=====
ttxtsubs: Found selected subtitles on PID 1024, page 792
-----
The subtitles for the language that you have selected is at teletext
page 792 on teletext PID 1024.
=====
ttxtsubs: Found non HI subtitles on PID 976, page 199
-----
You have selected subtitles for the hearing impaired, but on this
channel there are no such subtitles. Ttxtsubs uses the non hearing
impaired subtitles for the selected language instead.
=====
ttxtsubs: Wanted subtitle language(s) not found on channel, available languages:
889: fra (Subtitles)
-----
Subtitles for the language you have selected is not available on this
channel, but there are other alternatives, in this case French.
=====
ttxtsubs: Wanted subtitle language(s) not found on channel, available languages:
100: swe (Initial Page (The teletext start page, not a subtitles page!))
-----
This means that there is a start page for interactive teletext
browsing announced, but no subtitles. There may still be subtitles in
the teletext stream, but ttxtsubs won't find them since they are not
announced correctly. If so, double check that this is the case and
then contact the TV company, see above.
=====
ttxtsubs: No teletext subtitles on channel.
-----
No teletext stream at all was announced for this channel.
=====
ttxtsubs: Service Information read: timeout!
-----
No Service Information data could be found for 250 ms (a quarter of a
second). This could be an indication of bad reception, but may also be
because the cards tuner, a motorized antenna or a LNB hasn't yet
settled for the new channel. Ttxtsubs will retry for up to 10
seconds. Ttxtsubs will cache whatever it finally finds out about the
channel, so you will only see this happening at the most once for each
channel and vdr run.
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