[linux-dvb] receiving on a server and broadcasting to machines?

Stroller linux.luser at myrealbox.com
Fri Jan 5 19:24:51 CET 2007

On 5 Jan 2007, at 16:23, peter pilsl wrote:
> Not sure, if this is the right mailinglist ...  I would be happy if  
> anyone could point me to ...


> I want to to be able to watch TV on two of my laptops (maybe  
> different people looking different channels at the same time) So  
> instead of buying two expensive USB-DVB-cards, I was thinking about  
> buying one cheaper PCI-card and put it into the local server and  
> then broadcast all the channels over the intranet. I've seen such a  
> broadcast-option in my player Kaffeine.
> If it means that a client can connect to the server and request a  
> certain channel and then this channel is transmitted over the  
> network then I would probably be ok !?

You're pretty much describing a Linux-based "networked PVR" (personal  
video recorder) here. There are a couple of other projects besides  
MythTV, but I'll leave recommendations of others to others.

> So now I dont have much idea what this would mean for the cpu-load  
> and the network-load.
> ...
> The clients are connected via WLAN to the server and 20 MBit is a  
> realistic transfer-rate that is achieved all over the covered area.
> I dont have any clue how much bandwith a dvb-stream needs and if  
> the server "broadcasts" the original dvb-stream or an encoded  
> version or whatever.

Standard-definition (SD) TV, conventional digital TV and DVD-quality  
footage is fine, even on "re-purposed" machines and (I think) wifi.  
This is typically 720 x 480 pixels, I think. You would certainly not  
get more than 2 streams across wifi, tho'.

> If broadcast means that the server reads all channels simultanously  
> and send them over the network then the server and network would  
> break down within seconds I guess ... If it means that a client can  
> connect to the server and request a certain channel and then this  
> channel is transmitted over the network then I would probably be ok !?

Commonly the server ("backend") records one channel or one channel- 
per tuner card. It can stream one or more channels across the network  
and the clients ("frontends") tell the server when to change channels  
or stream a different recording.

> I dont even know if the client then has all abilities that dvb  
> brings : like stopping the TV and continue lateron - using  
> programpreview and so on.

Projects such as Myth have done all the work already, and provide a  
telly-like interface (or rather set-top-box-like interface) for these  

> The server is a old 500MHz-Celeron with 512MB which is more than  
> enough for a SOHO-fileserver but maybe not for dvb-server!? On the  
> other hand : I dont want to watch TV on that server. It should just  
> distribute the signal.

I _think_ that'd be ok, at least if you were capturing digital  
signals (using a DVD-T or DVB-S tuner card), although you wants loads  
of disk space for scheduled recordings. I would probably prefer to be  
using a 1ghz machine, myself. Transcoding - converting to a different  
compression-rate or -type - would be very slow on such a machine, but  
that may not matter if you can stream live; MythTV can automatically  
transcode recordings - so that they take up less space - in the  
background during idle time. The frontend machines should be > 1ghz  
for SD playback.

See you on the Myth mailing-list!


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