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Re: HDTV specification primer and a question

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  • jwpottberg
    Some of the info in this link may be helpful, though I don t know if it can be considered a primer : http://www.broadcast.net/~sbe1/8vsb/8vsb.htm Jim ... and
    Message 1 of 9 , Feb 6 5:08 PM
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      Some of the info in this link may be helpful, though I don't know if
      it can be considered a "primer":

      http://www.broadcast.net/~sbe1/8vsb/8vsb.htm

      Jim

      --- In HDTV-in-SFbay@yahoogroups.com, "Mr. Toad's" <junkmail@...>
      wrote:
      >
      > Hi all, it's my first post!
      >
      > I do audio and video compression for a living, mostly internet
      and
      > optical disc formats. I'd love to know where I could find a
      primer
      > on HDTV compression and error correction schemes, how the 6 MHz
      and
      > the bit rate relate to each other, etc. I know it won't exactly
      be
      > light reading. If anyone could refer me to any site on the net
      > that's worth looking into I'd much appreciate it.
      >
      > Also, something I've noticed... I'm watching both HDTV OTA and my
      mac
      > on the same 1080P projector. the mac is set to 1920 X 1080
      > (interlaced), presumably the OTA broadcast is the same 1920 X
      1080,
      > everything is HDMI 1.3 (tuner, cables, switcher, projector, the
      Mac
      > is DVI output into an HDMI convertor cable to the switcher) yet
      when
      > I switch back and forth between the two sources, they are
      different
      > sizes. The OTA signal is maybe 5% larger. Does this make any
      > sense? I did check the monitor options on the Mac to make sure
      that
      > overscan was off.
      >
      > To take that illustration one step further, when I boot the Mac
      the
      > projector shows the same size footprint that the OTA would show,
      then
      > resizes to about 5% less once the OS loads and the desktop kicks
      in.
      > I realize this isn't a Mac tech support forum, I'm more curious
      to
      > know why two devices set to 1920X1080 output are represented
      > differently. OTA HDTV is 1920 X 1080, right?
      >
      > Thanks in advance,
      >
      > Tardon
      >
    • Don Hackler
      Google this: dtv formats It will show you a bunch of useful sites.. The Wikipedia entries for Digital_television and High-definition_television are pretty
      Message 2 of 9 , Feb 6 5:31 PM
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        Google this: dtv formats
        It will show you a bunch of useful sites.. The Wikipedia entries for
        Digital_television and High-definition_television are pretty good.

        Most stations are sending 720p or 1080i on the HD channnels.

        The Mac video is probably being mapped pixel-to-pixel on your monitor,
        but the OTA video may be getting
        overscanned automatically by your monitor. (You didn't say how your OTA
        signal is getting to your monitor...)
        The Mac may be telling the monitor to disable the overscan when it is
        feeding the monitor.

        - Don

        Mr. Toad's wrote:
        > Hi all, it's my first post!
        >
        > I do audio and video compression for a living, mostly internet and
        > optical disc formats. I'd love to know where I could find a primer on
        > HDTV compression and error correction schemes, how the 6 MHz and the
        > bit rate relate to each other, etc. I know it won't exactly be light
        > reading. If anyone could refer me to any site on the net that's worth
        > looking into I'd much appreciate it.
        >
        > Also, something I've noticed... I'm watching both HDTV OTA and my mac
        > on the same 1080P projector. the mac is set to 1920 X
        > 1080 (interlaced), presumably the OTA broadcast is the same 1920 X
        > 1080, everything is HDMI 1.3 (tuner, cables, switcher, projector, the
        > Mac is DVI output into an HDMI convertor cable to the switcher) yet
        > when I switch back and forth between the two sources, they are
        > different sizes. The OTA signal is maybe 5% larger. Does this make
        > any sense? I did check the monitor options on the Mac to make sure
        > that overscan was off.
        >
        > To take that illustration one step further, when I boot the Mac the
        > projector shows the same size footprint that the OTA would show, then
        > resizes to about 5% less once the OS loads and the desktop kicks in.
        > I realize this isn't a Mac tech support forum, I'm more curious to
        > know why two devices set to 1920X1080 output are represented
        > differently. OTA HDTV is 1920 X 1080, right?
        >
        > Thanks in advance,
        >
        > Tardon
        >
        > On Feb 4, 2008, at 11:26 AM, toychinook wrote:
        >
        >> "Bit rate" is a very complicated issue, making the value of this
        >> number close to
        >> meaningless by itself.
        >>
        >> Today each OTA DTV station has 6 megahertz to use as they wish. 6
        >> megahertz is
        >> generally adequate for an HD program. But 40% of the bits in an OTA
        >> DTV broadcast are
        >> redundant (error correction) bits, not necessary in a cable broadcast
        >> since atmospheric
        >> noise is excluded.
        >
        >
      • Mr. Toad's
        Thanks Don, ... The Mac and the Tuner are both going DVI into the HDMI switcher. I m just switching back and forth between the two. Overscan is off on the
        Message 3 of 9 , Feb 6 5:53 PM
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          Thanks Don,


          The Mac video is probably being mapped pixel-to-pixel on your monitor, 
          but the OTA video may be getting
          overscanned automatically by your monitor. (You didn't say how your OTA 
          signal is getting to your monitor...)
          The Mac may be telling the monitor to disable the overscan when it is 
          feeding the monitor.










          The Mac and the Tuner are both going DVI into the HDMI switcher.  I'm just switching back and forth between the two.

          Overscan is off on the Mac.  I don't see any setup options on the tuner for over or underscan.  I wonder why a projector would automatically apply an over or underscan to one HDMI signal rather than another. Are there flags in a DTV signal that might indicate something like this?

          i was expecting that both were outputting 1920X1080 over HDMI and that the image would be the same size for each.  Hasn't worked out that way.  Note that the HDTV signal is the larger of the two.  The Mac boots up at the same pixel size, then resizes smaller when the desktop appears.

          Thanks for the interest,

          T


























          - Don

          Mr. Toad's wrote:
          > Hi all, it's my first post! 
          >
          > I do audio and video compression for a living, mostly internet and 
          > optical disc formats. I'd love to know where I could find a primer on 
          > HDTV compression and error correction schemes, how the 6 MHz and the 
          > bit rate relate to each other, etc. I know it won't exactly be light 
          > reading. If anyone could refer me to any site on the net that's worth 
          > looking into I'd much appreciate it.
          >
          > Also, something I've noticed... I'm watching both HDTV OTA and my mac 
          > on the same 1080P projector. the mac is set to 1920 X 
          > 1080 (interlaced) , presumably the OTA broadcast is the same 1920 X 
          > 1080, everything is HDMI 1.3 (tuner, cables, switcher, projector, the 
          > Mac is DVI output into an HDMI convertor cable to the switcher) yet 
          > when I switch back and forth between the two sources, they are 
          > different sizes. The OTA signal is maybe 5% larger. Does this make 
          > any sense? I did check the monitor options on the Mac to make sure 
          > that overscan was off. 
          >
          > To take that illustration one step further, when I boot the Mac the 
          > projector shows the same size footprint that the OTA would show, then 
          > resizes to about 5% less once the OS loads and the desktop kicks in. 
          > I realize this isn't a Mac tech support forum, I'm more curious to 
          > know why two devices set to 1920X1080 output are represented 
          > differently. OTA HDTV is 1920 X 1080, right?
          >
          > Thanks in advance,
          >
          > Tardon
          >
          > On Feb 4, 2008, at 11:26 AM, toychinook wrote:
          >
          >> "Bit rate" is a very complicated issue, making the value of this 
          >> number close to 
          >> meaningless by itself.
          >>
          >> Today each OTA DTV station has 6 megahertz to use as they wish. 6 
          >> megahertz is 
          >> generally adequate for an HD program. But 40% of the bits in an OTA 
          >> DTV broadcast are 
          >> redundant (error correction) bits, not necessary in a cable broadcast 
          >> since atmospheric 
          >> noise is excluded.
          >
          > 


        • luenlin
          Just a humble thought. Do the aspect ratios differ between hdtv and mac? I know for sure it is the case in PC graphics cards, where they support 16:10 and
          Message 4 of 9 , Feb 7 10:13 AM
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            Just a humble thought. Do the 'aspect ratios' differ between hdtv
            and mac? I know for sure it is the case in PC graphics cards, where
            they support 16:10 and hdtvs support 16:9

            -- Luen

            --- In HDTV-in-SFbay@yahoogroups.com, "Mr. Toad's" <junkmail@...>
            wrote:
            >
            > Thanks Don,
            >
            > >
            > > The Mac video is probably being mapped pixel-to-pixel on your
            monitor,
            > > but the OTA video may be getting
            > > overscanned automatically by your monitor. (You didn't say how
            your
            > > OTA
            > > signal is getting to your monitor...)
            > > The Mac may be telling the monitor to disable the overscan when
            it is
            > > feeding the monitor.
            > >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            > The Mac and the Tuner are both going DVI into the HDMI switcher.
            I'm
            > just switching back and forth between the two.
            >
            > Overscan is off on the Mac. I don't see any setup options on the
            > tuner for over or underscan. I wonder why a projector would
            > automatically apply an over or underscan to one HDMI signal rather
            > than another. Are there flags in a DTV signal that might indicate
            > something like this?
            >
            > i was expecting that both were outputting 1920X1080 over HDMI and
            > that the image would be the same size for each. Hasn't worked out
            > that way. Note that the HDTV signal is the larger of the two.
            The
            > Mac boots up at the same pixel size, then resizes smaller when the
            > desktop appears.
            >
            > Thanks for the interest,
            >
            > T
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            >
            > >
            > >
            > > - Don
            > >
            > > Mr. Toad's wrote:
            > > > Hi all, it's my first post!
            > > >
            > > > I do audio and video compression for a living, mostly internet
            and
            > > > optical disc formats. I'd love to know where I could find a
            > > primer on
            > > > HDTV compression and error correction schemes, how the 6 MHz
            and the
            > > > bit rate relate to each other, etc. I know it won't exactly be
            light
            > > > reading. If anyone could refer me to any site on the net
            that's
            > > worth
            > > > looking into I'd much appreciate it.
            > > >
            > > > Also, something I've noticed... I'm watching both HDTV OTA and
            my
            > > mac
            > > > on the same 1080P projector. the mac is set to 1920 X
            > > > 1080 (interlaced), presumably the OTA broadcast is the same
            1920 X
            > > > 1080, everything is HDMI 1.3 (tuner, cables, switcher,
            projector,
            > > the
            > > > Mac is DVI output into an HDMI convertor cable to the switcher)
            yet
            > > > when I switch back and forth between the two sources, they are
            > > > different sizes. The OTA signal is maybe 5% larger. Does this
            make
            > > > any sense? I did check the monitor options on the Mac to make
            sure
            > > > that overscan was off.
            > > >
            > > > To take that illustration one step further, when I boot the Mac
            the
            > > > projector shows the same size footprint that the OTA would
            show,
            > > then
            > > > resizes to about 5% less once the OS loads and the desktop
            kicks in.
            > > > I realize this isn't a Mac tech support forum, I'm more curious
            to
            > > > know why two devices set to 1920X1080 output are represented
            > > > differently. OTA HDTV is 1920 X 1080, right?
            > > >
            > > > Thanks in advance,
            > > >
            > > > Tardon
            > > >
            > > > On Feb 4, 2008, at 11:26 AM, toychinook wrote:
            > > >
            > > >> "Bit rate" is a very complicated issue, making the value of
            this
            > > >> number close to
            > > >> meaningless by itself.
            > > >>
            > > >> Today each OTA DTV station has 6 megahertz to use as they
            wish. 6
            > > >> megahertz is
            > > >> generally adequate for an HD program. But 40% of the bits in
            an OTA
            > > >> DTV broadcast are
            > > >> redundant (error correction) bits, not necessary in a cable
            > > broadcast
            > > >> since atmospheric
            > > >> noise is excluded.
            > > >
            > > >
            > >
            > >
            > >
            >
          • Mr. Toad's
            ... On the Mac I m directly setting the monitor dimensions to 1920 X 1080, and there is no way to choose monitor settings by aspect ratio. Also, the aspect
            Message 5 of 9 , Feb 7 4:06 PM
            • 0 Attachment

              On Feb 7, 2008, at 10:13 AM, luenlin wrote:

              Just a humble thought. Do the 'aspect ratios' differ between hdtv 
              and mac? I know for sure it is the case in PC graphics cards, where 
              they support 16:10 and hdtvs support 16:9






              On the Mac I'm directly setting the monitor dimensions to 1920 X 1080, and there is no way to choose monitor settings by aspect ratio.  Also, the aspect ratio appears consistent with 16:9, just smaller by 5% or so than the HDTV signal.

               I'm over it already, that's life on the bleeding edge.  I just have to zoom in with the projector if I switch to the Mac and I want the DVD or video to fill the screen to the edges, the same as the HDTV signal does.

              Oh, one last thing, the component input on the projector also projects the same size as the HDTV signal, so it appears to be the Mac chain that isn't playing right.

              Thanks,

              Tardon






              -- Luen

              --- In HDTV-in-SFbay@ yahoogroups. com, "Mr. Toad's" <junkmail@.. .> 
              wrote:
              >
              > Thanks Don,
              > 
              > >
              > > The Mac video is probably being mapped pixel-to-pixel on your 
              monitor,
              > > but the OTA video may be getting
              > > overscanned automatically by your monitor. (You didn't say how 
              your 
              > > OTA
              > > signal is getting to your monitor...)
              > > The Mac may be telling the monitor to disable the overscan when 
              it is
              > > feeding the monitor.
              > >
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > The Mac and the Tuner are both going DVI into the HDMI switcher. 
              I'm 
              > just switching back and forth between the two.
              > 
              > Overscan is off on the Mac. I don't see any setup options on the 
              > tuner for over or underscan. I wonder why a projector would 
              > automatically apply an over or underscan to one HDMI signal rather 
              > than another. Are there flags in a DTV signal that might indicate 
              > something like this?
              > 
              > i was expecting that both were outputting 1920X1080 over HDMI and 
              > that the image would be the same size for each. Hasn't worked out 
              > that way. Note that the HDTV signal is the larger of the two. 
              The 
              > Mac boots up at the same pixel size, then resizes smaller when the 
              > desktop appears.
              > 
              > Thanks for the interest,
              > 
              > T
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > 
              > >
              > >
              > > - Don
              > >
              > > Mr. Toad's wrote:
              > > > Hi all, it's my first post!
              > > >
              > > > I do audio and video compression for a living, mostly internet 
              and
              > > > optical disc formats. I'd love to know where I could find a 
              > > primer on
              > > > HDTV compression and error correction schemes, how the 6 MHz 
              and the
              > > > bit rate relate to each other, etc. I know it won't exactly be 
              light
              > > > reading. If anyone could refer me to any site on the net 
              that's 
              > > worth
              > > > looking into I'd much appreciate it.
              > > >
              > > > Also, something I've noticed... I'm watching both HDTV OTA and 
              my 
              > > mac
              > > > on the same 1080P projector. the mac is set to 1920 X
              > > > 1080 (interlaced) , presumably the OTA broadcast is the same 
              1920 X
              > > > 1080, everything is HDMI 1.3 (tuner, cables, switcher, 
              projector, 
              > > the
              > > > Mac is DVI output into an HDMI convertor cable to the switcher) 
              yet
              > > > when I switch back and forth between the two sources, they are
              > > > different sizes. The OTA signal is maybe 5% larger. Does this 
              make
              > > > any sense? I did check the monitor options on the Mac to make 
              sure
              > > > that overscan was off.
              > > >
              > > > To take that illustration one step further, when I boot the Mac 
              the
              > > > projector shows the same size footprint that the OTA would 
              show, 
              > > then
              > > > resizes to about 5% less once the OS loads and the desktop 
              kicks in.
              > > > I realize this isn't a Mac tech support forum, I'm more curious 
              to
              > > > know why two devices set to 1920X1080 output are represented
              > > > differently. OTA HDTV is 1920 X 1080, right?
              > > >
              > > > Thanks in advance,
              > > >
              > > > Tardon
              > > >
              > > > On Feb 4, 2008, at 11:26 AM, toychinook wrote:
              > > >
              > > >> "Bit rate" is a very complicated issue, making the value of 
              this
              > > >> number close to
              > > >> meaningless by itself.
              > > >>
              > > >> Today each OTA DTV station has 6 megahertz to use as they 
              wish. 6
              > > >> megahertz is
              > > >> generally adequate for an HD program. But 40% of the bits in 
              an OTA
              > > >> DTV broadcast are
              > > >> redundant (error correction) bits, not necessary in a cable 
              > > broadcast
              > > >> since atmospheric
              > > >> noise is excluded.
              > > >
              > > >
              > >
              > >
              > >
              >


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