i'v read the request about drone/slave-mode. the request is for high numbers of cards in a system.
today i use vdr as server for my dvb-s cards. but it's crazy to use a vdr only for stream tv over the network. a simple, for the user, system like tvheadend is realy better. let me tell about the distributed sytem idea...
my son have a own tv. in the livingroom i have another tv. my daugther have a tv. i want to watch tv on pc. my pc havn't any tv-card. my son gav a good place for dvb-t. in the livingroom i have a place for dvb-s (the cable ends here). if tvheadend have a list of other tvheadend devices it can use the other devices (like my pc without any frontend-device.... ok, i can connect to any online tvheadend, but witch is online?).
how can it work?
any tvheadend send cyclic a udp brodcast (witch other tvheadend is online) for automatic mode or i use a list of ip's for my known systems.
if i get a channel-request on my tvheadend and the device is busy (i record other channel, or the channels ar not serviced by my device) tvheadend request the known other tvheadendsystems and forwards the traffic form the other device. if it's possible with the htsp-protokoll only a redirect to other device is send.
to handle the devices correct i need a priority-list.
1. recording have first prio. if i record (and connected to any system) i can't intterrupt this. if any connected to my system and he record my distributed stream i can't change the channel (but i reqest over the network for other free device ;-) who can service my request).
2. my system have prio. if any use my tveadend (not for recording) the user is disconnected if i change the transponder/muxes. the disconnected system try any other free tvheadend to connect. yes if i zap the other gets connection-errors.
with this workflow, you can make a dvb-system-farm with many devices the network can handle. you don't need a big server to handle many card's. cheap and lowpower-systems can handle the dvb's at any places with networkconnection.
in a simplest way you can distribute the unfiltered data from the muxes and my local tvheadend split it. it handles the extern system like a dvb-device. only a command for tuning is required.
i hope you can understand this (with my bad englisch).