[mythtv-users] Re: DVB no-signal behavior

Kenneth Aafl°y ke-aa at frisurf.no
Fri Mar 26 21:56:56 EST 2004


>On Sun, 21 Mar 2004, Ville Vehvilainen wrote: 
>
>> I'm using MythTV with the TechnoTrend DVB-C card. In my area there are 
>> some DVB channels that do not broadcast continuosly, only having a signal 
>> when there is some actual programming underway. When trying to tune to one 
>> of these channels when there is no signal I get the following behavior: 
> ... 
>
>> The frontend does not cope well with this situation. It does not accept 
>> any keyboard input during the tuning attempt, and eventually returns to 
>> the menu. Subsequent attempts to watch liveTV result in the same behavior. 
> 
> Following up on my own post here - this ought to be a reply to Brian May's 
> DVB issue list, but my mailserver barfed and ate a couple days' worth of 
> messages... 

> In short: the "no-signal" behaviour also seems to appear in cases when the 
> channel is encrypted. We have here a couple of channels that show free 
> content most of the time, but occasionally have encrypted shows. My 
> TechnoTrend DVB-C card does not have any support for a CAM and thus can 
> _never_ decrypt those shows, so the responsibility for gracefully 
> handling those situations _must_ be on the application. 

> In these cases I have two options: hack the database to force Myth to tune 
> to another channel, or wait until the encrypted program ends. Both options 
> are very cumbersome and tend to have a really negative effect on the GAF. 

> This may well be (partially) a DVB driver issue; however, since MythTV is 
> already known to cope rather badly with unexpected data I'm inclined to 
> believe this is a Myth problem. 

It's a MythTV issue, and not a driver problem. The cause is that the code in 
MythTV does not check if there is an incoming stream before ending the tune. 
This is partly because of the layout of MythTV Capture Card code (ie. that a 
card is split into a tuner and it's recorder), and partly because of me 
beeing lazy when I reimplemented the DVB layer.

I've got a early adopter solution in my own tree, but it's kinda unstable. 
What it provides is a messagebox on the frontend (if no stream is available) 
that gives the choice of trying a bit more or backing out to the menu (which 
could be easily extended to support changing to another channel). If you 
would like a rough patch against cvs to work with, I'll be happy to provide 
some diffs against my tree.

Kenneth


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