[mythtv] DVB 7133 uk full dvb-t scan problems

[Stuart Auchterlonie]

On Thu, Aug 25, 2005 at 09:35:44PM +0100, John Pullan wrote:
> Using 7133, Full uk country scan (dvb-t)
> I'm seeing the scanner stop after it processes the first multiplex. It
> segv'd the first time I tried to run it with extra debug, so I ran it
> under gdb where it appeared to freeze. (so I've attached the gdb trace
> of that as well)
> 
> On the plus side it only created one multiplex :)
> 

I'm digging around this at the moment.

The SEGV comes from the SISCAN debug print attempt at the top of
ScanWizardScanner::scan(). A nice little #if 0 has temporarily
solved the problem.... :-)

The reason it is only creating one multiplex is because it is
getting stuck (or frozen..)

It looks like it is waiting for the card to tune.
Here is the relevant logs

--- mythtv-setup log ----

2005-08-26 11:27:25.426 SIScan(0): UpdatePATinDB(): mplex: 1:1
2005-08-26 11:27:25.426 GetBetterMplexID(mplexId 1, tId 8197, netId 1)
2005-08-26 11:27:25.485 GetBetterMplexID(): Returning perfect match 1
2005-08-26 11:27:25.606 SIScan(0): Tuning to  offset 1 mplexid(1)
2005-08-26 11:27:25.636 DVB#0 Frequency: 482000000 BW: 8MHz HP: Auto LP:
AutoC: Auto TM: 2K H: None GI: 1/32
2005-08-26 11:27:25.636 DVB#0 Waiting for event

--- end log ---

and from gdb

--- backtrace ---

#2  0xb7d1fc88 in get_dvb_event (fd=12, event=@0xb5977ca0, block=true)
at dvbchannel.cpp:869
#3  0xb7d1d2b3 in DVBChannel::TuneTransport (this=0x81b9fd8,
channel=@0x81ba0ec, all=false) at dvbchannel.cpp:620
#4  0xb7d15d2b in DVBChannel::TuneMultiplex (this=0x81b9fd8, mplexid=1)
at dvbchannel.cpp:176
#5  0xb7c2280c in SIScan::Tune (this=0x8152b30, transport={_it = {node =
0x818e008}, _offset = 1}) at siscan.cpp:665
#6  0xb7c2311f in SIScan::ScanTransport (this=0x8152b30, transport={_it
= {node = 0x818e008}, _offset = 1}) at siscan.cpp:724

--- end backtrace ---

so it is sitting in get_dvb_event getting EWOULDBLOCK back from
the FE_GET_EVENT ioctl.


Now I remember reading something in the last few days about what
the DVB API does when you request a tune to the frequency the
card is already tuned to (I think this was on linux-dvb mailing list)

I believe the answer that came back was that
a) No Event was delivered if the card had no change in tuning
b) You can't issue a FE_GET_STATUS until a FE_SET_STATUS(?) had be done.


More research to do...
Stuart