Cannot select 1920x1080 (interlaced) @50Hz outside of Media Centre

Discussion in 'Windows Media Center' started by Gareth D. Phillips, Nov 9, 2007.

  1. Hi. I am really struggling to find a solution to a problem as I dont know if
    it is an OS issue, or a driver issue but I am leaning toward OS... Any help
    would be very much appreciated.

    I have a fairly new ATI Radeon 2400Pro graphics card in my Vista 32-bit
    Ultimate machine. I chose this card as it is apparntly good for H.264
    playback etc. I have a 37" 1080i LCD TV which is connected to the card using
    DVI - HDMI (DVI on the card, HDMI on the TV)

    The best resolution the screen supports is 1080i (1920x1080) so I am making
    the assumption that HD video and Blu-Ray / HD-DVD is going to look best in
    this res (also the BBC broadcast in 1080i on the BBC HD channel in the UK)

    50Hz is very important in the UK as without running @ 50hz video on live TV
    or DVD etc is very glitchy. Here lies my problem:

    Within Media Cente if I try to select 1920x1080i @50Hz I CAN as long as I
    select "Select All Modes" and then scroll to the end of the list. The INFO
    feature on my TV confrims that the res is indeed 1080i (it doesnt confirm the
    refresh rate but the smoothness of video suggests that the signal is indeed
    50hz)

    The problem is there is no way I can select 50hz outside of Media Centre. In
    the display properties in control pannel if I select "list all modes" there
    are only options for 25 and 30hz if I recall. No 50hz and no 60hz. I can run
    in 1080i @30hz but video is not smooth at all. Instead I am forced to run in
    [email protected] As soon as I open Media Centre the refresh goes back to my desired
    1080i @50hz.

    Can anybody suggest why the 50hz option is unavailable for 1080i? I have
    tried the Catalyst control centre and even within this app there is no way of
    forcing this res. I am using the latest version of the card drivers (7.10).

    The card can surely do 1080i @50 as this is what Media Centre is set at! ?

    Thanks in anticipation.
     
    Gareth D. Phillips, Nov 9, 2007
    #1
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  2. Gareth D. Phillips

    RalfG Guest

    I think it's a case of misunderstanding how display resolution works and
    confusing refresh rate/line frequency with framerates. 1080i25 is the actual
    PAL display rate for 1080i HDTV resolution, there is no 1080i50 AFAIK. All
    the values for PAL and NTSC (etc) are dictated by the specifications for
    each mode. The video driver takes care of it all so you needn't be concerned
    about those details as long as you can pick the display resolution you need
    within the PAL format.

    1080i resoluton is an "interlaced" display mode while 720p resolution is
    "progressive" scan mode. Progressive scan is what a typical computer monitor
    uses, scanning every line sequentially, ie. @50hz for PAL, 60hz for NTSC.
    At interlaced resolutions like 1080i only every other line is scanned, so
    each half screen is displayed alternately, at 25hz for PAL and 30hz for
    NTSC. To the eye it appears as if the full screen is being displayed at
    nearly 50hz or 60hz. Your display would need to be "1080p" capable to work
    at the 50hz setting.

    The ATI Catalyst Control Center has the neccessary region settings for TV
    plus additional display settings for HDTV resolutions. You are able to force
    HDTV resolutions that aren't detected automatically but it isn't advisable
    to choose a resolution setting that your display isn't capable of .. such as
    1080p50 when its maximum resolution is 1080i25.
     
    RalfG, Nov 9, 2007
    #2
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  3. Thanks, I appreciate your help and I think you have clarified a lot. However
    despite kind of understanding what you are saying, I AM able to select 1080i
    @ 50 inside media centre (but not outside it) - this is definitley
    interlaced also - not P. I definitley cannot display 1080p
     
    Gareth D. Phillips, Nov 9, 2007
    #3
  4. Gareth D. Phillips

    RalfG Guest

    Previously you stated that no rate was listed in Media Center at 1080i and
    that you only assumed it was @50hz.
    Its still a question of misunderstanding, this time of the notation being
    used. Simply selecting 1080i in PAL mode is all that is required to get the
    correct display output.

    1080i in PAL mode only displays 50 half frames (fields) per second, which is
    equivelent to 25 full frames per second. It's not different from standard
    definition PAL TV (576i) in that way. Typically when Interlaced resolutions
    are quoted with a rate number it is the field rate, not the frame rate or AC
    line frequency that is meant, so 1080i50 means 1080 interlaced lines @50
    fields (=1/2 frames) per second. OTOH progressive scan resolutions like
    720p50 or 1080p60 do mean frame rates of 50fps or 60fps.

    ATI's own notation for HDTV resolution settings, from their Catalyst Help:

    a.. 720p60- Use this format for displaying 720p HDTV content broadcasted
    in traditional NTSC countries (North America and Japan).
    b.. 1080i30-Use this format for displaying 1080i HDTV content broadcasted
    in traditional NTSC countries (North America and Japan).
    c.. 1080p60-Use this format for displaying 1080p HDTV content broadcasted
    in traditional NTSC countries (North America and Japan).
    d.. 720p50-Use this format for displaying 720p HDTV content broadcasted in
    traditional PAL and SECAM countries (Europe, Australia, most of Asia, Africa
    and South America).
    e.. 1080i25-Use this format for displaying 1080i HDTV content broadcasted
    in traditional PAL and SECAM countries (Europe, Australia, most of Asia,
    Africa and South America).

    There's a pretty good description of interlaced resolutions here:

    http://en.wikipedia.org/wiki/Interlace

    And the PAL specification here:

    http://en.wikipedia.org/wiki/PAL
     
    RalfG, Nov 9, 2007
    #4
  5. Gareth D. Phillips

    jolt Guest

    The best resolution would actually be it's native resolution which for most
    37" LCDs would be 1366 x 768. If the native resolution is 768 and you set
    the output to 1080 the set will simply scale the display back to the native
    resolution. It's a little confusing but feeding the set it's native
    resolution looks best unless the scaler in the set is superior to the video
    cards scaling.
     
    jolt, Nov 10, 2007
    #5
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