Originally Posted by kenavs
You do have to go to the actual frequency that the station broadcasts on first, since the tuner has no way of knowing what the assigned frequency for the station is, other than to do a complete scan of all of the frequencies and searching for active stations. When it finds one, it reads the PSIP data to determine what the station is known as. During a full scan, the ATSC tuner would have found a digital station at UHF 15. The PSIP data would have told it that the station was known as 14 which is the frequency assigned to the station's analog(NTSC) transmitter and placed the entry in the channel memory.
The answer to the 3575's channel loss problem for analog cable users has been here all along... its name is "PSIP."
From the ATSC.org website (bold and caps added for emphasis): "The Program and System Information Protocol (PSIP) Standard, document A/65, is a collection of tables designed to operate within every transport stream for terrestrial broadcast of digital television. The purpose of the protocol is to facilitate the tuning of programs by specifying the information at the system and event levels for all virtual channels carried in a particular transport stream. Additionally, information for analog channels - as well as digital channels from other transport streams - MAY be incorporated."
Analog cable users are getting their digital channels thru an analog
feed (a "different transport stream") and the cableco isn't including the PSIP (they "MAY" but don't have to), so there is no PSIP to "facilitate the tuning of programs...." That is, analog cable users have no "tracking data" to maintain stability as they tune to or surf those channels.
I'm on basic analog cable and receiving 6 orphan digital channels... why would my cableco include the PSIP for those digital channels I'm not paying extra for?
The mandatory inclusion of PSIP for OTA transmission and digital cable is why people who use those feeds, like Suplex, get 37 or more rock-solid video channels!
Is this a problem statement with NO solution!?
Good stuff from PSIP.org website, esp. 2nd para.:
Program and System Information Protocol (PSIP) is data that is transmitted along with a station's DTV signal that tells DTV receivers important information about the station and what is being broadcast. The most important function of PSIP is to provide a method for DTV receivers to identify a DTV station and to determine how a receiver can tune to it. PSIP identifies both the DTV channel and the associated NTSC (analog) channel. It helps maintain the current channel branding because DTV receivers will electronically associate the two channels making it easy for viewers to tune to the DTV station even if they do not know the channel number.
In addition to identifying the channel number, PSIP tells the receiver whether multiple program channels are being broadcast and, if so, how to find them. It identifies whether the programs are closed captioned, conveys V-chip information, if data is associated with the program, and much more. If broadcasters do not include properly encoded PSIP data in their DTV signals, receivers may not correctly identify and tune to the station. Therefore, it is vital that all broadcasters understand PSIP and include the data in their DTV stations signals. PSIP is a mandatory Advanced Television Systems Committee (ATSC) Standard."