[mythtv] Potential bug in myth tv

[Charles Mason]

I am quite new to mythtv and have found what may be a potential bug. 
This could however be a problem with my set up I am not sure. The 
problem occurs when I am whatching live tv or recording tv. If I am 
whatching live tv  every thing works fine untill about 5 to 8 seconds 
after starting the viewing mythbackend crashes with the following message.

IOBOUND - blocking in ThreadedFileWriter::Write()

It then exits with a segfault. This only occurs on certian tv channels 
(uk tarestrial channels, ITV 1 Channel 5 and Five). BBC 1 and BBC 2 
behave as they a suposed to. The second I chanhe channels to one of the 
three listed aboive for about 5 seconds it crashes. I then decided to 
use gdb to get a stack trace this is shown below.

[New Thread 163851 (LWP 4902)]
IOBOUND - blocking in ThreadedFileWriter::Write()

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 131081 (LWP 4897)]
0x080b9319 in NuppelVideoRecorder::FormatTeletextSubtitles(VBIData*) (
    this=0x43681008, vbidata=0x46c1560c) at NuppelVideoRecorder.cpp:1584
1584        *outpos = 0;
(gdb) bt
#0  0x080b9319 in NuppelVideoRecorder::FormatTeletextSubtitles(VBIData*) (
    this=0x43681008, vbidata=0x46c1560c) at NuppelVideoRecorder.cpp:1584
#1  0x080ba12d in NuppelVideoRecorder::doVbiThread() (this=0x43681008)
    at NuppelVideoRecorder.cpp:1983
#2  0x080b8a95 in NuppelVideoRecorder::VbiThread(void*) (param=0x43681008)
    at NuppelVideoRecorder.cpp:1418
#3  0x4091a811 in pthread_start_thread () from /lib/i686/libpthread.so.0
#4  0x4091a915 in pthread_start_thread_event () from 
/lib/i686/libpthread.so.0


I do not know the mythtv codebase at all and so am not rearly sure what 
exactly is causing the problem. However as I read its something to do 
with the VBI system. As I understand it VBI is the system used to read 
the teletext data out of the tv signal. I have been having problems with 
disabling the subtitles on the BBC 1 and BBC 2 (the channels that apear 
to work ok). Simply pressing the t key causes the mythfront end to out 
put turning off tt to the terminal. This seems to have no effect though 
on the sub titles. I am not sure if this is realted. 

My setup is as follows.

Mandrake 9.1
AMD 1.4 Ghz CPU
512 meg DDR RAM
40 GB Hard Disk
Sound Blaster Live sound card (using drivers installed by Mandrake 9.1)
Geforce 2 64 MB (Using latest nvidia drivers)
Hauppauge Win TV pci (bt 878 based)


Could someone interprit the stack trace for me or has anyone got any 
idea of a solution to the problem?

Thanks for your help.

Charlie