[mythtv] QAM tuning problem with HD-3000 & kernel DVB drivers

Bruce Pennypacker bruce at pennypacker.org
Thu Jun 2 15:39:17 UTC 2005

> If this has already been answered sorry but I am catching up on the -dev list
> after a few days of ignoring it.. Are you using hte DVB drivers for starters? 
> (I have to assume you are if you are scaning).. Can you tune to some
> multiplexes where you know channels are and see if you can find an VCTs (i.e.
> data on PID 0x1FFB).. Some cable systems don't send VCTs from what I have
> gathered from the list and when the scaning app gets no meta data it just bails
> out and gives up.. I need to change this, but I need to know if you are getting
> VCTs very slowly, or if they are just not present at all..

Yes, I'm using DVB.  I'm using the HD-3000 DVB support built into the
2.6.11-rc3 kernel. (cx88-dvb module?)

I'm a real neophyte when it comes to all the DVB terminology so bear
with me but it looks like there's data on PID 0x1FFB.  Using the
linuxtv.org dvb-apps I have the following entry in my channels.conf:


If I run "azap -r C82" it shows a signal lock.  I then run dvbtraffic
and its output contains:

0800  1685 p/s   309 kb/s  2535 kbit
0801   131 p/s    24 kb/s   197 kbit
0802    69 p/s    12 kb/s   104 kbit
0840  2063 p/s   378 kb/s  3103 kbit
0841   132 p/s    24 kb/s   199 kbit
0842    67 p/s    12 kb/s   101 kbit
0880  2390 p/s   438 kb/s  3594 kbit
0881   130 p/s    23 kb/s   196 kbit
0882    68 p/s    12 kb/s   103 kbit
1fff  1530 p/s   280 kb/s  2302 kbit
2000 25804 p/s  4737 kb/s 38809 kbit

If I then modify my channels.conf using the PID's 880 & 881 (converted
to decimal) to this:


Then after running azap on this channel I can pipe
/dev/dvb/adapter0/dvr0 to mplayer and view the channel.

Another thing I found is that if I run azap on an OTA channel while
hooked up to an antenna then dvbscan will show output like this:

$ dvbscan -c
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
service is running. Channel number: 25:1. Name: 'FOX Television Boston MA'
dumping lists (1 services)
FOX Television Boston MA (0x0003) 00: PCR == V   V 0x0031 A 0x0034 (eng)
0x0034 (eng)

But if I have the cable hooked up and do the same on a QAM channel that
I've identified then the output is more like this:

$ dvbscan -c
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
WARNING: filter timeout pid 0x1ffb
dumping lists (11 services)
[0002]                   (0x0002) 00: PCR 0x0800          A 0x0801
0x0802 (spa)
[000b]                   (0x000b) 00: PCR 0x0840          A 0x0841
0x0842 (spa)
[0009]                   (0x0009) 00: PCR 0x0880          A 0x0881
0x0882 (spa)
[0008]                   (0x0008) 00: PCR 0x08c0          A 0x08c1
0x08c2 (spa)
[0003]                   (0x0003) 00: PCR 0x0900          A 0x0901
0x0902 (spa)
[0007]                   (0x0007) 00: PCR 0x0940          A 0x0941
0x0942 (spa)
[0001]                   (0x0001) 00: PCR 0x0980          A 0x0981
0x0982 (spa)
[000a]                   (0x000a) 00: PCR 0x09c0          A 0x09c1
0x09c2 (spa)
[0004]                   (0x0004) 00: PCR 0x0a00          A 0x0a01
0x0a02 (spa)
[000c]                   (0x000c) 00: PCR 0x0a40          A 0x0a41
0x0a42 (spa)
[0006]                   (0x0006) 00: PCR 0x0a80          A 0x0a81

> I will be glad to assist you, but chances are I will be digging into this for
> the next few days since my 5th gen Air2PC should be here tomorrow and I want to
> make it work with Cable as well as 8VSB since thats what is specd out to do..

I'll be more than happy to do whatever testing you might need.  As I
said before I don't know much about DVB, etc. but I used to develop
telephony software so I'm used to debugging in realtime streaming
environments.  I've got no problems firing up gdb & tracing through
things as long as you give me a good idea of what you're looking for.
Feel free to e-mail me directly whenever you're done with the Air2PC work.


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