[mythtv] re: mythtv with dvb is unusable!

Jason Hoos jhoos at thwack.net
Tue Nov 25 12:45:37 EST 2003


> If you wanted to investigate a programming solution, then I 
> guess looking at the code which reads from the socket.  I 
> guess we either need a non-blocking read and a select call, 
> or else an alarm which can spot that we have hung for more 
> than a certain amount of time.  
> 
> On the backend I suspect it's more complicated because the 
> DVB card is presumably supplying data ok, the problem is 
> presumably that the thread which decodes is not supplying 
> anything.  I think you would need to look carefully at the 
> CAM code in the backend to workout what to do there...

I believe (although I haven't tried it recently) that the same thing occurs
with the HDTV stuff if you tune to a channel with no signal.  A means to
break out of the situation on the frontend would certainly help, especially
if that solution can also signal the backend to stop trying to decode a bad
signal.  What might actually be ideal would be for one end or the other to
detect the situation and just display a "No Signal" message on the screen,
so that you could still flip to another channel, as opposed to being dropped
out of Live TV mode or something like that.  Not sure what you'd do with
recording in this situation though, perhaps somehow encode blank frames?  (I
imagine doing that would be a major headache...)

I know that the pcHDTV drivers have ioctls for checking signal strength; do
the ivtv drivers have something similar, and might they help for something
like this?  Or would it be better to just somehow detect when we have
received a slew of undecodeable frames (one would hope that the "bad packet"
bits in the transport stream would be set in this case)?

Jason




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