QAM is one form of modulation. It is standardized, but as is the case with many standards, there are many of them, such as 8VSB. QAM is more efficient, hence many systems are moving to it, but not all.
ATSC defines the signaling, contained within the modulated (and often encrypted) carrier. This is where the standards parameters for 720p, 1080i, etc... are defined. Different carriers can indeed map different channels, use sub-channels (i.e. xxx.1), etc... however if you have a tuner/cablecard setup capable of demodulating the chesen scheme and is ATSC compliant, then grabbing the channels is trivial, as they are all in standardized "locations" within the carrier. The encryption is the biggie... -sc > -----Original Message----- > From: hank [mailto:hgedr...@myrealbox.com] > Sent: Thursday, September 10, 2009 7:08 AM > To: NT System Admin Issues > Subject: RE: [OT] web -> HDTV > > Not an expert. The signaling is standard (QAM) but since the channels > are > virtual they can be mapped anywhere (and sometimes change). The cable > box > gets this mapping information from the cable head end. Other equipment > doesn't. I have a homebuilt DVR (MythTV) and some folks in that > community > figured out how to scan for the channel allocations. > > The other requirement is that a normal tuner can only display > unencrypted > QAM. Some cable operators encrypt more than they need to. > > > -----Original Message----- > From: bounce-8653286-8231...@lyris.sunbelt-software.com > [mailto:bounce-8653286-8231...@lyris.sunbelt-software.com] > Sent: Thursday, September 10, 2009 01:31 > To: NT System Admin Issues > Subject: RE: [OT] web -> HDTV > > I looked at this for a few days with my cousin a couple of months ago, > he > has HD Dish and HD Cox cable and wanted to watch the HD channels on his > mediapc w/ bluray. He currently sees all the standard channels but HD > is > just grey screen. We looked at 6-7 different cards and they all appear > to > sneakily say' over air HD' or in other words antenna based HD. > > Speaking to a rep at Fry's electronics, he said there is no standard > signaling for HD between vendors like it is with analog TV so you cant > find > a card to accommodate all of the different signaling being used. IDK if > I > believe that but it does kind of make sense. > > > > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > > > ---AV & Spam Filtering by M+Guardian - Risk Free Email (TM)--- > > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
