[mythtv] Failed DVB recording

[Tom Hughes]

In message <e558cc3b4d.tom at loxley.compton.nu>
        Tom Hughes <tom at compton.nu> wrote:

> In message <1108064943.420bbaaf3b10f at www.digitalregime.com>
>           Taylor Jacob <rtjacob at earthlink.net> wrote:
>
>> Quoting Tom Hughes <tom at compton.nu>:
>> 
>> > I had a DVB recording fail last night. The relevant log extract is:
>> 
>> > 2005-02-09 18:30:04.271 DVB#0 DVB signal 5300 | snr 5000 | ber 143af12 | unc
>> > 7961d18
>> > 2005-02-09 18:30:04.273 DVB#0 Status: LOCK.
>> > 2005-02-09 18:30:04.273 DVB#0 Multiplex Locked
>> > 2005-02-09 18:30:10.966 DVB#0 Timeout Getting PMT
>> > 2005-02-09 18:30:11.096 DVB#0 ERROR - Tuning for channel #4 failed.
>> > 2005-02-09 18:30:11.176 Changing from None to RecordingOnly
>> > 2005-02-09 18:30:11.237 DVB#0 Recorder: Card opened successfully (using PS
>> > mode).
>> > 2005-02-09 18:30:12.265 DVB#0 WARNING - No data from card in 1 second.
>> > 2005-02-09 18:30:13.316 DVB#0 WARNING - No data from card in 1 second.
>> > 2005-02-09 18:30:14.318 DVB#0 WARNING - No data from card in 1 second.
>> >
>> > Obviously it failed to tune the right channel due to a timeout
>> > getting the PMT from the multiplex. I don't know what the cause
>> > of that was, but what happened afterwards is that it continued
>> > to pretend it was recording and spew out those "No data" messages
>> > for the duration of the program.
>> 
>> Can you tune to this multiplex with zap and look at the PMT deltas?  There is
>> currently a 5 second PMT timeout when attempting to get the PIDs for the
>> desired channel.  The average PMT delta is .1 to .2 seconds, so I suspect that
>> there was some issue with the deilvery of it.
>
> OK. I've worked out how to do this now by tuning with tzap and then
> using dvbsnoop to look for the PMT data. They are coming in about
> every 0.19 seconds most of the time - one or are longer but the longest
> that I've seen is about 0.35 or so.

I've had this happen a few more times recently so I decided to try
increasing the timeout to see if it helped but I when I went to look
at the code I found that the timeout is not actually 5 seconds but
is just 0.3 seconds which would explain why I'm having problems as
my gaps between PMTs are sometimes as long as 0.35 seconds.

The code in DVBChannel::Tune does 3000 iterations of the loop and
sleeps for 100us on each pass which gives 300000us or 0.3 seconds.

I've just upped it to 30000 iterations to give a 3 second timeout
and am rebuilding at the moment to see if that improves thing. It
will probably take a few weeks before I'm really sure though as it
doesn't fail very often.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://www.compton.nu/