[mythtv-users] Can't Open HDTV Card

R. G. Newbury newbury at mandamus.org
Mon Jan 1 08:49:36 UTC 2007

Gray wrote:
> Thank you for the response :) 
>> 1) Determining if your card is working.
>> Do you have a folder structure under /dev/dvb ??? 
>> You should have /dev/dvb/adapter0 and under that a demux0, frontend0 and 
>> dvr0 folders.
> Yes I have all of these folders :)
> -rwxrwxr-x 1 mythtv mythtv 27646 Dec 31 16:18 dtvscan
> I ran the dtvscan file.  It checked 109 channels just like the mythsetup
> did.  
> Question: how do I know if it scanning for ATSC signals or DVB?
> *[mythtv at localhost dvb-atsc-tools-1.0.4]$ ./dtvscan
> dtvscan ver 1.0.4 - by Jack Kelliher (c) 2002,2005,2006
> Attempting to open /dev/dtv
> Opened FE:/dev/dvb/adapter0/frontend0 4
> Opened DMX:/dev/dvb/adapter0/demux0 5
> Opened DVR:/dev/dvb/adapter0/dvr0 6
> channel = 2 VSB_8
> channel = 3 VSB_8
> channel = 4 VSB_8
> channel = 5 VSB_8
> channel = 6 VSB_8
> channel = 7 VSB_8
> channel = 8 VSB_8
> channel = 9 VSB_8
You don't show the full command line. You should be using:

dtvscan -q -dvb 0 -c 2:150 -o output. The -q is only for QAM256 and you 
want an output file.
A channels.conf looks like this for QAM256: the important number being 
the last one: the serviceid.


> I only showed a few of the 109 results.  None seem to have any signal?
> Are the VSB_8 digital channels?
  If not is it scanning for Analog
> channels? 
  How do I correlate the channel Number to the OTA assigned
> channel number? 
Run the scan properly and you should see channel designations like 18.1

  For example for my location channel number 18.1 is the
> CW channel digitally broadcast OTA signal(Webantenna site) is is
> actually channel 17 according to the FCC? Oh to make it more confusing
> some are shown as HD and I am told there is a format called SD and I am
> clueless about the difference.  But once we can determine if the card is
> working or at least scanning for Digital channels then maybe we tune to
> the proper signals?
Lots of stations transmit HD and SD versions of the same program on 
different subchannels  18.1/18.2 etc.

> Then I tried the dtvsignal check on several of the known high strength
> digital channels; the ones that should have lined up with my local
> broadcast channels and all showed as Signal: 000.
> [mythtv at localhost dvb-atsc-tools-1.0.4]$ ./dtvsignal 35
> using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
> tuning to 599000000 Hz
> video pid 0x0021, audio pid 0x0024
> dtvsignal ver 1.0.4 - by Jack Kelliher (c) 2002,2005,2006
> channel = 35 freq = 599000000Hz
> 30db       0%         25%         50%         75%        100%
> Signal:     |     .     :     .     |     ._____:_____._____|
> Signal: 000 .
>> You can then use the azap program to tune your card to a particular  
>> stream, and mplayer to play the stream (mplayer 
>> dvb://dev/dvb/adapter0/dvr0 is the command IIRC).
> I tried to find the azap program you are referring to apparently it is a
> PChtdv tool but no biggie because you have stated it is the same as the
> dtvscan program anyways.  I don't know how to stream to mplayer though?
> I am not sure by the statement:(mplayer  
>> dvb://dev/dvb/adapter0/dvr0 is the command IIRC) if this is a command I should run?

Azap and atscscan are part of the dvb-apps package available at linuxtv.org.
You run azap, with a tuning file (Cable-Qam256, etc.) to produce a 
listing of digital streams, and a data dump which is a raw channels.conf 
with unique names for each stream.

Then you use azap and the raw file, to tune your card. You can then cat 
the output from /dev/dvb/adapter0/dvr0 to a file test.mpg, and play the 
file with mplayer test.mpg, to see whether the stream is playable. There 
is also a way to play the stream directly.

Browse the mythtv wiki: there are pages referred to which cover this in 


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