[mythtv] Re: Adding DVB-T support to MythTV

[Edward Wildgoose]

I just posted some notes on DVB to myth-users because I couldn't remember where I had seen this thread.  
 
There seems to be an easy and a hard way to do this.  The easy way is to use a pipe against the mpg stream (I think you can even use mjpeg tools for this?).  You would then need a fairly simple unix sockets application to emulate the receiving socket.  I think something simple could be knocked up in perl, but I wonder if it wouldn't cause synchronisation problems with audio (assuming audio is actually decoded?).  Buffering problems would also be an issue I guess.
 
The hard but better way would be to bypass the decode and re-encode step altogether.  This will require a change to myth (possibly substantial if adding an mpeg decoder is not straightforward).  Basically myth can avoid reading from /dev/video0, encoding and putting into the record file, but reading directly from /dev/dvb.  However, on playback it will then be decoding mpeg whereas the current system only appears to decode mjpeg or MPEG4 (is that right?)
 
The DVB project is doing exactly this and quote use of a AMD 450Mhz machine, so resources are obviously a lot lower if you don't need to encode (and quality is probably a lot higher by avoiding the redundant decode/encode step).
 
Sounds like an interesting project anyway.

-----Original Message-----


I have also posted this suggestion to the list. See my earlier post with my idea about channel changing scripts - what is needed is something to parse a seperate config file between channel numbers and dvbtune frequencies. As far as acutally using the card, I've only just got mine and haven't even tried it yet. Does the dvb driver actually create a v4l interface ( I think it creates a /dev/dvb device but is this a standard v4l interface ) ? The docs for the dvb driver are v.beta and it's complicated stuff. I belive in the full featured dvb-s cards ( with an onboard mpeg decoder ) this is a v4l interface so it would work out the box with mythtv once an external channel change script is available If the interface can't be connected to directly via mythtv using the /dev/dvb interface as a v4l interface, then your other option is to use a seperate mpeg card ( for example the realmagic hollywood plus ) which with the dvb driver it is possible to s! ! end the mpeg output from the dvb-t card into the mpeg card and out through the tv out on the mpeg card as decoded video. This output could then be rerouted back in through another cheap wintv card, which can be used by mythtv. This is a bit of a messy workaround involving three cards to do the work of one - I'm not a programmer but there should be a way to either decode the mpeg output of the dvb-t card in software and create a v4l interface which mythtv can use. I looked around at just doing this with pipes - to convert the transport or program stream and then pipe it to a virtual v4l interface. I can decode the stream to various video formats using pipes but couldn't find any answer about how to make a decoded stream available as a /dev/video. Anyone got any clues on piping streams direclty to a virtual /dev/video ? The problems associated with this approach would probably be timing issues due to the high level of processing going on. However, it would be interesting to hav e! ! the discussion and see what else is thrown up. 


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