[linux-dvb] Problem with Avermedia AverTV DVB-T USB2.0 (a800)

Patrick Boettcher patrick.boettcher at desy.de
Thu Aug 11 08:18:10 CEST 2005

Hi Matt,

On Wed, 10 Aug 2005, Matt Holgate wrote:
> I'm having an intermittent problem with my Avermedia USB2.0 DVB-T a800 box. 
> I'm running kernel 2.6.13-rc6 and built the latest drivers from dvb-kernel 
> CVS (I also tried the drivers distributed with 2.6.13-rc6).
> The problem seems to happen about 50% of the time, and occurs when the 
> channel is set using tzap (also built using latest dvb-apps CVS). If I run 
> tzap, then use dvbstream piped into mplayer (in another terminal), then about 
> half the time it seems to tune correctly, the other half I get a blocky 
> corrupt mess.

I can confirm this observation. Unfortunately there is a bug somewhere in 
either dvb-usb or even dvb-core. I'm not sure where to look:

> Oddly, tzap seems to think it is locked onto the signal. Even more strangely, 
> it always gives 2 plausible lines of output, followed by all subsequent lines 
> with a signal strength of 0, an SNR of ffff and a ber and unc of 0! (note 
> that it does this whether or not the tuning is successful). Surely something 
> is wrong there, as the values do not seem at all sensible (see below).

Don't rely on SNR and Signal strength. They are not calculated correctly 
and thus wrong. Rather rely on BER and UNC (the lower there better the 

And also tuning _is_ always successful (as you can see on UNC and BER). 
The problem is, that somewhere the arriving MPEG2-TS data is not handled 

Can you please try the following:

run tzap -r "BBC One Scot" and let mplayer play /dev/dvb/adapter0/dvr0 
directly (you don't need dvbstream, when playing locally).

When mplayer appears to have the blocky picture, try to run dvbscan -c, 
while tzap is still running.

It if won't time out, but put out the channels of this frequency, than the 
problem is probably the software-demuxer (unlikely), otherwise it is a bug 
in the dvb-usb-framework...

Sorry for this mess,

   Mail: patrick.boettcher at desy.de
   WWW:  http://www.wi-bw.tfh-wildau.de/~pboettch/

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