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  1. #21
    Join Date
    Jan 2008
    Location
    Montreal
    Posts
    4,784
    Quote Originally Posted by Donovan's Monkey View Post
    But the ABC and CW stations from Rochester NY broadcast on the same frequency. ABC is 13-1, CW is 13-2, with both broadcast in HD, so apparently it is possible to have a sub-channel in HD. Although in this case both are 720p, not the 1080i used by all of the Canadian stations that I am aware of.
    You are reffering to WHAM-TV.

    It's possible for 2x 720p feeds to co-exist on the same channel, with a lot of stretching (see this wiki: http://en.wikipedia.org/wiki/Digital...nnel#Tradeoffs )

    But the issue remains the same: There's only 19.4 Mbps of bandwidth to share. A few months ago, Global Toronto HD had a 18.5 Mbps video feed with 2 audio feeds (384 kbps each), using up the whole allocated 19.4 Mbps so the video feed was superb. (It is now 15.5 Mbps)

    When multiplexing, the main channel lose picture quality. If a station broadcast 2 HD feeds at equal bitrate, the feeds are reduced to a max of 9.3 Mbps video each (add 384 Kbps for audio), which is crap for MPEG-2 compression. So, choices have to be made: quality or quantity?

    By the way, it's also possible to broadcast a 480i image in 16:9 format (ex: WCAXtra 3.2 Burlington). It's not because a digital subchannel fills your HDTV screen that it's necessarily high definition.

    On a semi-related subject, the CRTC secured mandatory carriage of MétéoMedia and The Weather Network on cable/satellite until 2018, but since subdigital OTA channels have to be approved by the CRTC and the fact that canadian networks won't launch a subchannel if they ain't carried on cable and/or satellite, it probably means that no local canadian station will dare launching an OTA weather updates channel.
    "It's not a rerun if you haven't watched it yet." (© 2010 by TVViewer)
    "Ne jamais s'obstiner avec un épais. Il va vous abaisser à son niveau et vous battre avec l'expérience."

  2. #22
    Join Date
    Aug 2007
    Location
    Toronto area
    Posts
    1,048
    Quote Originally Posted by InMontreal View Post
    ... By the way, it's also possible to broadcast a 480i image in 16:9 format (ex: WCAXtra 3.2 Burlington). It's not because a digital subchannel fills your HDTV screen that it's necessarily high definition. ...
    I did not know that. I haven't seen it done yet, but it probably would be better to broadcast a sub-channel in 16:9 if the source image was that aspect ratio.
    Now I'm not sure what the WHAM Rochester ABC/CW set-up is. I looked at wikipedia, and it seems to indicate The CW WHAM-DT2 13-2 is SD. I can usually receive the Rochester UHF stations, but almost never the VHF stations, so I can't just easily check it myself. This site stated that both The CW and ABC were 720p on WHAM 13, but maybe it's possible they saw The CW 13-2 in 16:9 as you suggested, and incorrectly assumed it was HD.
    Last edited by Donovan's Monkey; 08-08-2011 at 09:53 PM.

 

 

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