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

Richard King rak at cs.man.ac.uk
Tue Mar 18 18:54:49 EST 2003

Hi Matt,

> Yep, I think MJPeg tools would definitely do the conversion to various
> different video formats, while ts2ps would demultiplex the initial
> transport stream.
It will. though as as I said in my last message you're going to have to 
have a way of telling ts2ps which PID's you want.  

> The only problem then is to get this stream into a
> virtual v4l interface ( if indeed this is possible ). I did look around
I'm not sure this is the most useful way of doing it. Myth currently 
doesnt support incoming MPEG2 streams from a V4L device and I'm not sure 
the V4L api supports datastreams with both the audio and video embedded. 
It would certainly take a while to implement this in Myth so you might as 
well write some direct support into Myth.

If you meant decoding the MPEG2 stream and then feeding it into the V4L 
subsystem this is definately possible with something like vloopback 
(though it might need a bit of work to get it into a useful shape for 
this - disclaimer: only looked at it for 2 mins :S ) This method is going 
to be incredibly wasteful of resources though.

> on the web to try and find out if it's possible to pipe a stream in this 
> way but couldn't find anything referring to similar stuff - if anyone 
> knows how to do this I will certainly test it out. I would also imagine 
> there would be timing and synchronising issues. 
vloopback looks like a good start. You said in another mail that it only 
supports sending from a V4L device, my initial impressions suggest this is 
not the case, though they are VERY initial impressions ;) AFAICS vlookback 
requires you to feed a virtual V4L device (say /dev/video0) and it will 
then mirror than input out on another V4L device (say /dev/video1). As 
long as you have a program that can feed it the video in the right format 
it should work

> As I said in my previous mail the channel changing would require a 
> script and a config file. The config file lists the channel frequencies 
> on the dvb signal, and cross references them to the mythtv epg. This 
> would need to be filled somehow by tv_grab_uk, or perhaps generated 
> automatically by another script. The channel change script would then 
> convert the mythtv channels to the correct frequency and call dvbtune. 
In some countries it should be possible to get the data for the EPG out of 
the transport stream. (I think freeview in the UK only broadcasts Now and 
Next information right now though)

> However, even on the initial feedback to this post it certainly looks 
> like there is some interest so here's hoping someone picks this up and 
> runs with it. I'm available for testing, documentation and other 
> non-programmer type stuff ..... 
This is my /big/ project when I finish uni this summer, assuming I'm not
beaten to it. My intention is to make Myth support a form of plugins to
support various inputs with my target being: V4L, DVB and internet
streams; with FM radio, DAB and American Digital TV/HDTV being easily
supported if someone wanted to write the support.

Richard King
E-mail: rak at cs.man.ac.uk

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