[mythtv] Assistance debugging a DVB/PMT tuning problem

Mark Paulus mark.paulus at verizonbusiness.com
Thu Jan 24 16:09:20 UTC 2008



Tom Dexter wrote:
> On Jan 23, 2008 5:01 PM, Tom Dexter <digitalaudiorock at gmail.com> wrote:
>> On Jan 23, 2008 4:42 PM, Janne Grunau <janne-mythtv at grunau.be> wrote:
>>> The cable provider doesn't seem to transmit a PMT
>>> on the announced PID. I don't know where dvbscan gets the video and
>>> audio from. running dvbsnoop on PID 0x0 and 0x30 might give further
>>> hints.
>>>
>>>
>>> Janne
>> Thanks Janne!  This is broadcast by the way, not cable.
>>
>> I'm installing dvbsnoop now and will see what it shows.
>>
>> Tom
>>
> Wow...is this turning into an exercise in futility...
> 
> I've never had a need before to use any of these various utilities
> before.  I'm assuming that in order to use dvbsnoop I need something
> to tune in the station.  I have
> media-tv/linuxtv-dvb-apps-1.1.1.20070114 installed under Gentoo which
> has both the dvbscan I used before and tzap, which I want to use to
> tune the channel.  From everything I can gather, tzap apparently wants
> a channels.conf format that looks something like this (from the mythtv
> wiki):
> 
> SBS DIGITAL 1:564500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_64:...
> SBS DIGITAL 2:564500000:INVERSION_AUTO:BANDWIDTH_7_MHZ:FEC_2_3:FEC_2_3:QAM_64:...
> 
> ...but no matter how I run dvbscan (even with -o zap, which is
> supposed to be the default) I get a format like I posted earlier:
> 
> WNJB-DT:183028615:8VSB:49:52:3
> NJN-3:183028615:8VSB:81:84:5
> NJN-4:183028615:8VSB:97:100:6
> 
> ...which causes tzap to error out with "ERROR: error while parsing
> inversion (syntax error)". I installed dvbtune, and that errors out
> with "Unknown FE type. Aborting".  From what I'm reading that's caused
> by changes in the DVB api.  The only option I could actually get
> working was to let mythbackend do the tuning...but since mythtv can't
> actually receive that channel, my only option was to plug the channel
> number 58.1 into the cardinput table and start the frontend...jeeeez.
> 
> Anyway, doing that I was able to run 'dvbsnoop -n2 0x0', but trying
> 0x30 just hung with no output.  Here's the output using 0x0:
> 
> dvbsnoop V1.4.00 -- http://dvbsnoop.sourceforge.net/
> 
> ------------------------------------------------------------
> SECT-Packet: 00000001   PID: 0 (0x0000), Length: 24 (0x0018)
> Time received: Thu 2008-01-24  10:11:21.607
> ------------------------------------------------------------
>   0000:  00 b0 15 07 d9 cd 00 00  00 03 e0 30 00 05 e0 50   ...........0...P
>   0010:  00 06 e0 60 56 39 47 43                            ...`V9GC
> 
> PID:  0 (0x0000)  [= assigned for: ISO 13818-1 Program Association Table (PAT)]
> Guess table from table id...
> PAT-decoding....
> Table_ID: 0 (0x00)  [= Program Association Table (PAT)]
> section_syntax_indicator: 1 (0x01)
> (fixed): 0 (0x00)
> reserved_1: 3 (0x03)
> Section_length: 21 (0x0015)
> Transport_Stream_ID: 2009 (0x07d9)
> reserved_2: 3 (0x03)
> Version_number: 6 (0x06)
> current_next_indicator: 1 (0x01)  [= valid now]
> Section_number: 0 (0x00)
> Last_Section_number: 0 (0x00)
> 
>     Program_number: 3 (0x0003)
>     reserved: 7 (0x07)
>     Program_map_PID: 48 (0x0030)
> 
>     Program_number: 5 (0x0005)
>     reserved: 7 (0x07)
>     Program_map_PID: 80 (0x0050)
> 
>     Program_number: 6 (0x0006)
>     reserved: 7 (0x07)
>     Program_map_PID: 96 (0x0060)
> 
> CRC: 1446594371 (0x56394743)
> ==========================================================
> 
> 
> ------------------------------------------------------------
> SECT-Packet: 00000002   PID: 0 (0x0000), Length: 24 (0x0018)
> Time received: Thu 2008-01-24  10:11:21.686
> ------------------------------------------------------------
>   0000:  00 b0 15 07 d9 cd 00 00  00 03 e0 30 00 05 e0 50   ...........0...P
>   0010:  00 06 e0 60 56 39 47 43                            ...`V9GC
> 
> PID:  0 (0x0000)  [= assigned for: ISO 13818-1 Program Association Table (PAT)]
> Guess table from table id...
> PAT-decoding....
> Table_ID: 0 (0x00)  [= Program Association Table (PAT)]
> section_syntax_indicator: 1 (0x01)
> (fixed): 0 (0x00)
> reserved_1: 3 (0x03)
> Section_length: 21 (0x0015)
> Transport_Stream_ID: 2009 (0x07d9)
> reserved_2: 3 (0x03)
> Version_number: 6 (0x06)
> current_next_indicator: 1 (0x01)  [= valid now]
> Section_number: 0 (0x00)
> Last_Section_number: 0 (0x00)
> 
>     Program_number: 3 (0x0003)
>     reserved: 7 (0x07)
>     Program_map_PID: 48 (0x0030)
> 
>     Program_number: 5 (0x0005)
>     reserved: 7 (0x07)
>     Program_map_PID: 80 (0x0050)
> 
>     Program_number: 6 (0x0006)
>     reserved: 7 (0x07)
>     Program_map_PID: 96 (0x0060)
> 
> CRC: 1446594371 (0x56394743)
> ==========================================================
> 
> Hopefully that worked correctly, given the kludged way I had to go
> about it.  I'd love to get tzap working correctly with the right
> channels.conf format and retry scanning 0x30.  That format doesn't
> appear to be documented anywhere I can find.
> 

Doing a google for 'tzap channels.conf' led me to this page, which
might be helpful for settting up your channels.conf file:
http://brej.org/dvb/

I use the following script to help me investigate Transport Streams
captured via my QAM-256 card from my cable provider.  It finds 
all the info about your stream, PAT, PMT and PID info:

for i in "$@"
do
    dvbsnoop -n 10 -nph -s ts -tssubdecode -if "$i" > "$i.dvbsnoop"
done

To create a file, I use 'dvbstream <-c card> -o 8192 > file.ts'
dvbstream can be found out there on the web somewhere.  Hmmm.  Looks
like I am using a debianized version, so should be no problems finding
a version.
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