Originally Posted by mabuttra
Originally Posted by WillN937
My observation is that the PSIP data is ephemeral and is sent on pretty much a continuous basis. I say this because anytime you want to refresh the data you can just tune to a channel and frequently the data for a time block comes and goes. By that I mean you can be looking at the guide for a channel and the info will disappear and then a few seconds or minutes later will reappear.
The disappearing and reappearing data seems to be a bug in the DTVPal. There is no question that tuning to a channel will download that stations guide data for how ever many hours they send out. The question has always been how frequently, when the DTVPal is in standby mode, the DTVPal does a channel sweep to keep the guide filled in for all the channels. My PSIP data seems to update about every 2 hours.
Disappearing/reappearing data has also been reported on the CM-7000Pal thread. It's mostly a problem with extended show descriptions, it seems.
There are recommendations re: how often to send guide data, but they are very lax:
EIT-0: (the 3-hour block containing the show currently airing): repeat at least every 0.5 seconds
EIT-1: (the next 3-hour block): repeat at least every 3 seconds
EIT-2 and up: repeat at least every minute
Luckily almost everyone sends out guide data much more frequently. Nobody wants to remain tuned to a single frequency for 60 seconds to pick up more than a few hours of guide info - especially if you have 20-30 RF channels to check! But extended descriptions are sent in different tables, the ETTs, and those are repeated less often.
What the Pal puts into its guide should be a function not only of how often the Pal scans for updates, but also how long it "listens" to each frequency and what data the station happens to transmit during each "listening" interval.
I've observed that when you're tuned to a station, it will update the listings for that station more or less continuously. On occasion, that does seem to involve deleting info (particularly extended descriptions), which will fill back in once the appropriate data is received again.