Please explain "sub-channels"

Discussion in 'Archived Threads 2001-2004' started by Chris White, Jul 25, 2001.

  1. Chris White

    Chris White Second Unit

    Joined:
    Feb 12, 1999
    Messages:
    391
    Likes Received:
    0
    Trophy Points:
    0
    The local hdtv stations are listed with a normal channel number. For example:
    WESH-DT NBC Channel 11
    WFTV-DT ABC Channel 39
    WKMG-DT CBS Channel 58
    However, whenever I see someone refer to ABC, they say it is actually channel 39.1. Sorry if this seems like a stupid question, but does this mean that if I had a high definition receiver and wanted to watch ABC, that I would set the channel to 39.1? Are all digital stations this way? In other words, are the channels listed above really 11.1, 39.1, and 58.1??
    I'm concerned about this because I want to be able to connect a high definition receiver to both my tv (component cable) and to my Replay (s-video cable). BUT, as I understand it, the Replay is not capable of tuning in a sub-channel such as 39.1 If there is a cable channel 39 and a digital channel 39, the Replay can handle that - it simply renumbers one of them as channel 1039 (or something like that).
    ------------------
    The Whites' Home Theater Website
    Pictures, DIY Projects, Glossaries, FAQ, Links, Toshiba Tips & Tweaks
     
  2. Chip_Slattery

    Chip_Slattery Stunt Coordinator

    Joined:
    Jan 10, 2001
    Messages:
    151
    Likes Received:
    0
    Trophy Points:
    0
    Chris,
    Basically what it boils down to is that each digital channel does map out as you describe (39.1, 39.2 or 39-1,39-2). This is known as "multicasting" and allows a single digital station to provide SD programming on up to four sub-channels. Imagine the following:
    39.1 = Normal programming
    39.2 = 24 hour local weather
    39.3 = interactive programming
    39.4 = 24 hour "home shopping"-type channel
    For a more in-depth (and probably more accurate [​IMG]) explanation take a look at this site.
    I'm not familiar with ReplayTV so hopefully someone else can help you out on that question.
    Hope this helps to clear it up a bit.
    Chip
    [Edited last by Chip_Slattery on July 25, 2001 at 12:14 PM]
     
  3. Stephen Tu

    Stephen Tu Screenwriter

    Joined:
    Apr 26, 1999
    Messages:
    1,573
    Likes Received:
    0
    Trophy Points:
    0
    Not only are there subchannels, but there is the issue of channel number remapping. Suppose the normal analog broadcast of ABC was on channel 7. Now the digital broadcast is on channel 39, but the station can also broadcast instructions that tell your receiver to still display/select the channel number as 7, so that people don't have to learn the new digital channel numbers. So it might be, depending on
    your receiver
    7 - old analog broadcast
    7.1 - digital channel 39 subchannel 1 (HDTV)
    7.2 - digital 39 sub 2 (SD, or alternate programming)
    etc.
    Not all subchannels are always active, and they might be showing several SD channels, one HD and 1/2 SD, any of a number of combinations. The programs could be the same program in different formats, or different programs entirely.
    What's worse, for the channel remapping, is that sometimes that equipment that broadcasts the remapping data goes down, and then it changes back to 39. (HDTV is still in its infancy!)
    As for Replay (and Tivo for that matter), it has no knowledge about digital channels, subchannels or remapping, so that means you basically have to use manual timers to set up the recording, if you want to record OTA stuff, and use timers also on the HDTV settop, or change the channel yourself. Eventually, when there are enough settops out there, presumably the PVR mfgers will update their software to deal with these issues.
    Another issue with current settops is that you can't watch in HD and record in SD simultaneously; there is a mode switch and if you leave it in "HD" then Replay won't record anything. Generally I recommend getting a 2nd cheap, non-HD receiver to use as a Replay slave.
     
  4. Chris White

    Chris White Second Unit

    Joined:
    Feb 12, 1999
    Messages:
    391
    Likes Received:
    0
    Trophy Points:
    0
    Thanks guys. I understand now. I don't like it, but I understand. It looks like I basically have a choice to make - watch hdtv with commercials or cable tv (via the Replay) without commercials.
     
  5. Todd Hochard

    Todd Hochard Cinematographer

    Joined:
    Jan 24, 1999
    Messages:
    2,312
    Likes Received:
    0
    Trophy Points:
    0
     
  6. Chris White

    Chris White Second Unit

    Joined:
    Feb 12, 1999
    Messages:
    391
    Likes Received:
    0
    Trophy Points:
    0
    Even though the Replay will only record 480i, my hope was that the 480i feed from a set top box would be a much cleaner signal than what I'm currently getting from Adelphia cable. TWC may have a long wait for its STBs, but just be thankful you're not stuck with Adelphia.
    I've decided I'm not going to buy a receiver yet. If it weren't for Replay, I wouldn't watch much tv at all. So until there is a set top box that integrates satisfactorily with the Replay, I'll wait. If I were to buy one today it would probably be the Samsung since 1) the Samsung is the only unit that will output both 1080i and 480i at the same time and 2) all I want is OTA reception. However, the Samsung does not have a serial data input for control by the Replay, unlike the Sony HD100. I understand Zenith is developing a combination receiver/pvr so I may just wait for that.
     
  7. Allan Jayne

    Allan Jayne Cinematographer

    Joined:
    Nov 1, 1998
    Messages:
    2,404
    Likes Received:
    0
    Trophy Points:
    0
    Yet another use of these sub-channels is different camera (viewing) angles you can choose from, say for a football game.
    So don't cast aside the complication of dot one or dot 2 after the (main) channel number -- yet.
    Other video hints: http://members.aol.com/ajaynejr/video.htm
     

Share This Page