Mailing List Archive: MythTV: Dev

Error: Wrong PMT and Failed CRC check after UK freeview network changes

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roger at beardandsandals

Nov 24, 2009, 4:20 AM

Post #1 of 5 (1324 views)
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Error: Wrong PMT and Failed CRC check after UK freeview network changes

After the recent DVB transmission network changes here if the north west
of England my rescanning of transports on mythtv 0.21 installation
seemed to have worked OK (after a few hiccups involving the the
transport scan picking up frequencies from the main transmitter not the
relays out of the NIT). However after a while I noticed that one channel
was not picking up EIT(EPG) information. This channel was BBC2,
serviceid 4287 on transportid 4168. Other channels on the same transport
appeared to getting updated guide data fine.

I turned on eit and siparser logging and noticed the following errors
being logged when I switched live tv to the BBC2 channel (which viewed
perfectly!).

2009-11-23 17:44:42.324 PESPacket: Failed CRC check 0x76174442 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:43.322 PESPacket: Failed CRC check 0x76174443 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:44.327 PESPacket: Failed CRC check 0x76174444 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:45.323 PESPacket: Failed CRC check 0x76174445 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:46.323 PESPacket: Failed CRC check 0x76174446 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:47.328 PESPacket: Failed CRC check 0x76174447 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:48.325 PESPacket: Failed CRC check 0x76174448 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:49.313 PESPacket: Failed CRC check 0x76174449 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:50.327 PESPacket: Failed CRC check 0x76174450 !=
0xc3bfa4b5 for StreamID = 0x70
2009-11-23 17:44:51.324 PESPacket: Failed CRC check 0x76174451 !=
0xc3bfa4b5 for StreamID = 0x70
...
2009-11-23 17:44:53.715 DTVSM(201) Error: Wrong PMT; pmt->pn(6016)
desired(4287)
2009-11-23 17:44:53.721 DTVSM(201) Error: Wrong PMT; pmt->pn(4544)
desired(4287)
2009-11-23 17:44:53.722 DTVSM(201) Error: Wrong PMT; pmt->pn(4288)
desired(4287)
2009-11-23 17:44:53.723 DTVSM(201) Error: Wrong PMT; pmt->pn(4608)
desired(4287)
2009-11-23 17:44:53.724 DTVSM(201) Error: Wrong PMT; pmt->pn(4672)
desired(4287)
2009-11-23 17:44:53.726 DTVSM(201) Error: Wrong PMT; pmt->pn(4352)
desired(4287)
2009-11-23 17:44:53.727 DTVSM(201) Error: Wrong PMT; pmt->pn(4736)
desired(4287)
2009-11-23 17:44:53.728 DTVSM(201) Error: Wrong PMT; pmt->pn(4168)
desired(4287)

I then used dvbsnoop to look at the PAT and PMT. The PAT showed that the
PMT for 4287 was being transmitted on PID 200 and the snoop for this PID
produced a correctly formatted PMT with the correct program number (4287).

I then noticed that I never saw a PAT for the correct transport (4168)
being built, other numerous other ones were. My suspicion is that
somehow an old PAT is being used although a quick glance through the
database did not produce any obvious candidates for where it might be
stored. So my first question is. Does myth cache PATs and if so where?
If it doesn't then how does it determine which PMT pids to look at?

Also I wonder if the CRC errors are something to do with this as they
occur immediately before the Wrong PMT errors are logged.

I do not want to upgrade to 0.22 (it does not seem to be available on
debian.multimedia yet) before I have bottomed this out.

Any ideas anyone?

Thanks,

Roger
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mythtv-dev mailing list
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roger at beardandsandals

Nov 25, 2009, 6:36 AM

Post #2 of 5 (1175 views)
Permalink

Re: Error: Wrong PMT and Failed CRC check after UK freeview network changes [In reply to]

Roger James wrote:
> After the recent DVB transmission network changes here if the north
> west of England my rescanning of transports on mythtv 0.21
> installation seemed to have worked OK (after a few hiccups involving
> the the transport scan picking up frequencies from the main
> transmitter not the relays out of the NIT). However after a while I
> noticed that one channel was not picking up EIT(EPG) information.
> This channel was BBC2, serviceid 4287 on transportid 4168. Other
> channels on the same transport appeared to getting updated guide data
> fine.
>
> I turned on eit and siparser logging and noticed the following errors
> being logged when I switched live tv to the BBC2 channel (which viewed
> perfectly!).
>
> 2009-11-23 17:44:42.324 PESPacket: Failed CRC check 0x76174442 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:43.322 PESPacket: Failed CRC check 0x76174443 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:44.327 PESPacket: Failed CRC check 0x76174444 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:45.323 PESPacket: Failed CRC check 0x76174445 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:46.323 PESPacket: Failed CRC check 0x76174446 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:47.328 PESPacket: Failed CRC check 0x76174447 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:48.325 PESPacket: Failed CRC check 0x76174448 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:49.313 PESPacket: Failed CRC check 0x76174449 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:50.327 PESPacket: Failed CRC check 0x76174450 !=
> 0xc3bfa4b5 for StreamID = 0x70
> 2009-11-23 17:44:51.324 PESPacket: Failed CRC check 0x76174451 !=
> 0xc3bfa4b5 for StreamID = 0x70
> ...
> 2009-11-23 17:44:53.715 DTVSM(201) Error: Wrong PMT; pmt->pn(6016)
> desired(4287)
> 2009-11-23 17:44:53.721 DTVSM(201) Error: Wrong PMT; pmt->pn(4544)
> desired(4287)
> 2009-11-23 17:44:53.722 DTVSM(201) Error: Wrong PMT; pmt->pn(4288)
> desired(4287)
> 2009-11-23 17:44:53.723 DTVSM(201) Error: Wrong PMT; pmt->pn(4608)
> desired(4287)
> 2009-11-23 17:44:53.724 DTVSM(201) Error: Wrong PMT; pmt->pn(4672)
> desired(4287)
> 2009-11-23 17:44:53.726 DTVSM(201) Error: Wrong PMT; pmt->pn(4352)
> desired(4287)
> 2009-11-23 17:44:53.727 DTVSM(201) Error: Wrong PMT; pmt->pn(4736)
> desired(4287)
> 2009-11-23 17:44:53.728 DTVSM(201) Error: Wrong PMT; pmt->pn(4168)
> desired(4287)
>
> I then used dvbsnoop to look at the PAT and PMT. The PAT showed that
> the PMT for 4287 was being transmitted on PID 200 and the snoop for
> this PID produced a correctly formatted PMT with the correct program
> number (4287).
>
> I then noticed that I never saw a PAT for the correct transport (4168)
> being built, other numerous other ones were. My suspicion is that
> somehow an old PAT is being used although a quick glance through the
> database did not produce any obvious candidates for where it might be
> stored. So my first question is. Does myth cache PATs and if so
> where? If it doesn't then how does it determine which PMT pids to look
> at?
>
> Also I wonder if the CRC errors are something to do with this as they
> occur immediately before the Wrong PMT errors are logged.
>
> I do not want to upgrade to 0.22 (it does not seem to be available on
> debian.multimedia yet) before I have bottomed this out.
>
> Any ideas anyone?
>
> Thanks,
>
> Roger
After much logging and looking at the code and my database setup, I can
only conclude that this is related to the CRC errors. I think the wrong
PMT error is a red herring as I have not seen it again for a couple of
days. However there a lots of CRC errors and service 4287 still does not
get any EIT data. dvbsnoop does not report any crc errors. I have line
of sight to the transmitter which is less than a mile away so
transmission errors are unlikely. The StreamID of 0x70 is not a valid
PES stream ID as far I can see all valid ones should have the top bit
(0x80) set and the received CRC increasing by one on each packet looks
very suspicious. Googling for the Failed CRC error reveals a lot of
cases where the stream ID of 0x70 is reported.

Once again has anyone got any thoughts on this?

Roger
_______________________________________________
mythtv-dev mailing list
mythtv-dev [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev

stuart at tase

Nov 25, 2009, 6:48 AM

Post #3 of 5 (1169 views)
Permalink

Re: Error: Wrong PMT and Failed CRC check after UK freeview network changes [In reply to]

On Wednesday 25 Nov 2009 14:36:32 Roger James wrote:
> After much logging and looking at the code and my database setup, I can
> only conclude that this is related to the CRC errors. I think the wrong
> PMT error is a red herring as I have not seen it again for a couple of
> days. However there a lots of CRC errors and service 4287 still does not
> get any EIT data. dvbsnoop does not report any crc errors. I have line
> of sight to the transmitter which is less than a mile away so
> transmission errors are unlikely. The StreamID of 0x70 is not a valid
> PES stream ID as far I can see all valid ones should have the top bit
> (0x80) set and the received CRC increasing by one on each packet looks
> very suspicious. Googling for the Failed CRC error reveals a lot of
> cases where the stream ID of 0x70 is reported.

The CRC errors are unrelated. 0x70 is an unimportant stream which has no CRC
hence the errors, but they don't explain the issue you are seeing.

A dump of your channel and dtv_multiplex tables to pastebin.ca might be
helpful.
--
Stuart Morgan
_______________________________________________
mythtv-dev mailing list
mythtv-dev [at] mythtv
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-dev

roger at beardandsandals

Nov 25, 2009, 9:29 AM

Post #4 of 5 (1160 views)
Permalink

Re: Error: Wrong PMT and Failed CRC check after UK freeview network changes [In reply to]

Stuart Morgan wrote:

On Wednesday 25 Nov 2009 14:36:32 Roger James wrote:
After much logging and looking at the code and my database setup, I can only conclude that this is related to the CRC errors. I think the wrong PMT error is a red herring as I have not seen it again for a couple of days. However there a lots of CRC errors and service 4287 still does not get any EIT data. dvbsnoop does not report any crc errors. I have line of sight to the transmitter which is less than a mile away so transmission errors are unlikely. The StreamID of 0x70 is not a valid PES stream ID as far I can see all valid ones should have the top bit (0x80) set and the received CRC increasing by one on each packet looks very suspicious. Googling for the Failed CRC error reveals a lot of cases where the stream ID of 0x70 is reported.
The CRC errors are unrelated. 0x70 is an unimportant stream which has no CRC hence the errors, but they don't explain the issue you are seeing. A dump of your channel and dtv_multiplex tables to pastebin.ca might be helpful.

Stuart,

Tables pasted to

http://pastebin.ca/1687035"]http://pastebin.ca/1687035

Source 1 is DVB-T(freeview) and source 5 is DVB-S(freesat).

The BBC2 channel is at line 691 and the PSB1 (old MUX 1) mux is at line 697.

multirec is enabled on all adapter cards.

The problem only appears to affect BBC2 on DVB-T. For the time being I have put an xmltvid on the BBC 2 DVB-T channel so I do get some listings on it. This was not set whilst I was doing the tests and there were no listings for that channel in the program table. The BBC 1 channel also did not have an xmltvid at that time but that did seem to be be getting listings from the EIT data.

I feel I must be missing something obvious here.

Thanks,

Roger

roger at beardandsandals

Nov 29, 2009, 12:19 PM

Post #5 of 5 (1083 views)
Permalink

Re: Error: Wrong PMT and Failed CRC check after UK freeview network changes [In reply to]

Roger James wrote:

Stuart Morgan wrote:
On Wednesday 25 Nov 2009 14:36:32 Roger James wrote:
After much logging and looking at the code and my database setup, I can only conclude that this is related to the CRC errors. I think the wrong PMT error is a red herring as I have not seen it again for a couple of days. However there a lots of CRC errors and service 4287 still does not get any EIT data. dvbsnoop does not report any crc errors. I have line of sight to the transmitter which is less than a mile away so transmission errors are unlikely. The StreamID of 0x70 is not a valid PES stream ID as far I can see all valid ones should have the top bit (0x80) set and the received CRC increasing by one on each packet looks very suspicious. Googling for the Failed CRC error reveals a lot of cases where the stream ID of 0x70 is reported.
The CRC errors are unrelated. 0x70 is an unimportant stream which has no CRC hence the errors, but they don't explain the issue you are seeing. A dump of your channel and dtv_multiplex tables to pastebin.ca might be helpful.
Stuart,

Tables pasted to

http://pastebin.ca/1687035"]http://pastebin.ca/1687035

Source 1 is DVB-T(freeview) and source 5 is DVB-S(freesat).

The BBC2 channel is at line 691 and the PSB1 (old MUX 1) mux is at line 697.

multirec is enabled on all adapter cards.

The problem only appears to affect BBC2 on DVB-T. For the time being I have put an xmltvid on the BBC 2 DVB-T channel so I do get some listings on it. This was not set whilst I was doing the tests and there were no listings for that channel in the program table. The BBC 1 channel also did not have an xmltvid at that time but that did seem to be be getting listings from the EIT data.

I feel I must be missing something obvious here.

Thanks,

Roger

I finally tracked this down to an out of date transportid field in the multiplex table. All working now.

Roger

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