[mythtv-users] Re: DVB Issues

Kenneth Aafl°y ke-aa at frisurf.no
Fri Mar 26 22:28:08 EST 2004

>> 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. 
> Hmmm... Wondered what happened if you waited long enough... Normally I 
> get impatient and abort with Ctrl+C at the console. 

It's usually stuck in a event handler (i think), so it won't respond.

>> Because of that, and since the backend is fixated on that 
>> channel, there seems to be no easy way to tune to another, 
>> working one! 

See my DVB post a bit earlier.

>> To get the system back running I have to use the channel 
>> editor or hack the database so that the channel in question 
>> is one that is actually showing some programming. 

> Been there, done that! 
> Another way is to: 
> 1. stop backend. 
> 2. change "first channel" for DVB card, with mythtv-setup or
> database editor.  
> 3. restart backend.

Think, that's what he meant!

> However, killing the backend like this is rather inconvenient...
> (I have the TV in my lounge room display live from my analog card,
> forcing MythTV to allow me to show live from the DVB card in my
> bedroom; when ever I reset the backend I have to reset everything
> else, too).

Yea, kinda annoying, ain't it?

> There should be some way of changing the channel (eg. with command
> line utility) via the backend without trying to receive a video
> feed.

Command line util???

There should be some protection against a recording/livetv getting started and 
no video show, yes..look for a previous posting by me.

> Also, on the topic of DVB: 
> * we have radio feeds broadcast via DVB here. I stupidly tried to
> setup one with no video PID but an audio PID. Same problem
> reoccurred as above.  

This should be coupled with the mythmusic stuff, which will get easier with 
the new music layer in development right now.

> * MythTV needs to realize that things can go wrong, and it shouldn't
> die in a heap if for some reason it can't get any signal. Just
> display a message "No signal received" and try to go back to a
> working channel. Obviously there will be cases where no channels 
> work (eg. some fool unplugs antenna), it needs to be able to
> gracefully cope with this too. I am using 0.14, this might be fixed
> in CVS?  

Agree here, there is far to litte error checking in the RingBuffer amongst 
others, the problem is that once you try to improve one condition in there, 
it usually has unwanted side effects..this could be a candidate for a branch 
of the libmythtv lib, so the error checking conditions could be fixed without 
affecting main development. I have some fixes in my tree, that makes it 
easier for the backend to react on errors, but it's very much experimental.

> * Same DVB channels have no analog equivalents and some analog
> channels have no DVB equivalent. I suspect MythTV can't cope very
> well with either case. eg. I have a suspicion that MythTV would try
> to record channel 31 on DVB, as DVB is preferred for recordings,
> even though channel 31 doesn't have any DVB settings defined (not
> tested).  

This is really not a problem with the DVB code per see, because it just does 
what it's told. If you configure one video-source for each card, this won't 
happen. The problem is with partially shared video-sources.

> * MythTV *really* needs to be able to load DVB channels directly from
> channels.conf file; this could be loaded directly into the database
> (some table may be required to map channels from channels.conf into
> MythTV channels) or by the backend directly reading the 
> channels.conf file. Probably the first better fits into the existing  
> MythTV model, I would image it shouldn't be too difficult either. Is 
> anybody doing anything like this? I don't want to re-invent the wheel. 

Yeah, either transforming (again) the dvb database to a vdr format specifier 
(so that a vdr file virtually can be copyed into the database), or an import 
feature in the channel editor would be great. I'm not going to do it however, 
as I've got too much to work on already (a private project taking far too 
much time).

> * Aspect ratio. DVB is wide aspect ratio. This displays fine on a
> computer screen. When displaying it on TV using the decoder in a 
> PVR350, the decoder "squashes" the image up to fit into standard 
> 4:3, which is obviously wrong. Pushing "W" cycles through modes 
> without any effect. Ideally I would like 2 modes:  
Have you tried the cvs of mythtv from after say about 2-3 months? There was a 
great addition that calculates the correct aspect ratio from your XFree 
DisplaySize/DPMS Values? Or maybe I just read that wrong, the PVR don't 
support scaling yet?, in wich case it would belong on the ivtv forum/mailing 
list, btw. when's there gonna be a forum for mythtv? :)

> * Issues with not being able to change channels need to get fixed in
> latest DVB driver code (assuming they haven't already been fixed in CVS).

You said that already, remember?


Kenneth Aafl°y
ke-aa at frisurf.no

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