[mythtv-users] Mooting architecture for a DataDirect replacement

Rod Smith mythtv at rodsbooks.com
Fri Jun 22 19:18:16 UTC 2007

On Friday 22 June 2007 14:25, Jay R. Ashworth wrote:
> We're a bit early in the game to be in a position to be required to go
> reverse engineer everyone else's solutions, and I have a day job, and a
> family, just like lots of other people.
> If there are people who a) have Copious Free Time, and b) tcpdump and
> c) those PVR's, I'd be happy to hear input.

I don't know a lot of details, but I do know that TiVo uses at least three 
methods for program distribution, depending on the box type:

1) DirecTV units obtain most (all?) of their guide data from DirecTV's
   digital guide data feed. Obviously this isn't an option for MythTV,
   at least not unless/until somebody comes out with hardware to
   directly receive satellite signals on a PC and Linux drivers for said
   hardware. (I believe such things exist in Europe, but not in the US,

2) Standalone (SA) TiVos record paid programming with digitally encoded
   data. This is usually on the Discovery Channel, IIRC, and the
   program looks like a bunch of blinking squares on the screen surrounding
   a message that says, in effect, that this is TiVo guide data. I don't
   know the details of how this data is encoded.

3) SA units also receive guide data via daily phone calls, which go through
   a dial-up ISP. The protocol involved is HTTP (or perhaps a secure variant
   of the same); TiVo operates a server for this purpose. I don't know how
   the data are encoded -- that is, what sort of file format is used. I
   don't believe the file format is really an issue, though.

So basically, what MythTV does now with Zap2It is quite similar to what TiVo 
does, at least for method #3. Method #2 wasn't always used; in TiVo's early 
days, it was all done via #3. I *PRESUME* that method #2 was implemented as a 
cost-cutting measure, to reduce load on their server and the bill from the 
ISP(s) they use to handle user dial-up traffic. Similarly, your method uses 
NNTP to minimize the costs on the community -- if we wanted to use the same 
protocols we use now but just set up our own server, we'd need to pay for it 
in some way. Most of us already pay for NNTP via our ISPs, so it's a logical 
choice to use to minimize costs.

Rod Smith

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