· Broadcast Engineer
Conventional ad hoc digital sat delivery uses 4 slots (directly adjacent slices of the bandwidth each on a separate frequency) per transponder, typically fed ad hoc by 4 separate uplinks from separate sources, which allows 4 different clients to timeshare the transponder on demand at any given time, simultaneously. Since DBS uses all of the xponder all of the time, they instead send a single MPTS (multiple program transport stream) which is one wideband carrier with the modulation holding the elemental programs from 4 sources all in the same stream. DISH leverages this by arranging the spot beams for the big 4 on the same xponder in each market.dpeters11 said:...I couldn't figure out how it's possible to use one tuner to get 4 networks at the same time, but in other places it sounds like it isn't recording them in the traditional sense.
A conventional DVR/IRD demodulates the MPTS signal and then demuxes the program signal of interest, discarding the rest. That then goes to the HDD for playback. IOW, even a conventional DVB tuner can (has the bandwidth to) see the entire transponder at once, but conventionally, only a fraction of the MPTS (a single program) is recorded.
The Hopper does not demux directly after demod, but sends the entire MPTS to the HDD. Then, at playback, it does the demux.
So there is nothing new as far as the technology goes, but moving the demux to playback is what makes PTA possible (that, along with fast CPUs and large HDDs).
This, of course, implies that it is impractical to save one show from a recording that actually holds 4 simultaneous shows since the file size is 4 times larger, and why to save a show past the 8-day expiration they have to basically do a playback/rerecord in the background from that partition to the user partition. Pretty slick implementation of conventional pro technology for consumer use, if you ask me. DirecTV will be close behind.
So no, not in the traditional sense (as far as consumer technology goes; TV stations have used this for backhaul for years). But not exactly magical, either.