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Am I seeing an analogue picture?

RichardcoulterRichardcoulter Posts: 30,301
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in Technical #1
I have a digital STB connected to an analogue CRT TV.

A friend says that the way that this works is by the STB converting the signal into analogue so that my old TV can display the digital signals.

Therefore, am I seeing an analogue or digital picture at the end of the process?:confused:

Thanks.

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  • chrisjrchrisjr Posts: 33,282
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    #2
    Richardcoulter wrote: »
    I have a digital STB connected to an analogue CRT TV.

    A friend says that the way that this works is by the STB converting the signal into analogue so that my old TV can display the digital signals.

    Therefore, am I seeing an analogue or digital picture at the end of the process?:confused:

    Thanks.
    It could be argued that all TV pictures as displayed on the screen are analogue. Simply because the way our eyes work is analogue. We perceive images as variations in intensity and frequency of light that vary continuously, analogue style rather than digital.

    So you could say that the word digital only really applies to the method by which the images are transported from their source to your TV screen. Once they arrive at your TV they become analogue in nature otherwise you would not be able to make much sense of what you are seeing.
  • RichardcoulterRichardcoulter Posts: 30,301
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    #3
    chrisjr wrote: »
    It could be argued that all TV pictures as displayed on the screen are analogue. Simply because the way our eyes work is analogue. We perceive images as variations in intensity and frequency of light that vary continuously, analogue style rather than digital.

    So you could say that the word digital only really applies to the method by which the images are transported from their source to your TV screen. Once they arrive at your TV they become analogue in nature otherwise you would not be able to make much sense of what you are seeing.

    Interesting, thank you. So even digital TV's with a built in Freeview tuner eventually turn into analogue!

    I always thought that the way that it worked was that the digital signals were compressed to get more channels in and that the digi boxes decrompressed them to make them watchable.

    I also always assumed that TV's with a built in Freeview tuner would give better pictures because there is no digi box to pass through; maybe if the signal has to be turned into analogue anyway it doesn't make any difference.
  • misarmisar Posts: 3,031
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    Leaving aside "It could be argued that all TV pictures as displayed on the screen are analogue", your friend is correct. An analogue CRT TV knows nothing about digital signals and is receiving the same analogue input from your STB (typically via a SCART cable) that it would have received from an ancient analogue device such as a VHS recorder.
  • chrisjrchrisjr Posts: 33,282
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    #5
    Richardcoulter wrote: »
    Interesting, thank you. So even digital TV's with a built in Freeview tuner eventually turn into analogue!

    I always thought that the way that it worked was that the digital signals were compressed to get more channels in and that the digi boxes decrompressed them to make them watchable.

    I also always assumed that TV's with a built in Freeview tuner would give better pictures because there is no digi box to pass through; maybe if the signal has to be turned into analogue anyway it doesn't make any difference.
    What you see coming off the screen has to be analogue because we perceive the world in an analogue manner.

    The raw digital signal coming off a HD studio camera would need almost the entire capacity of all the muxes on Freeview combined to transmit the amount of data generated. So some form of data compression has to take place if you want more than one channel to watch :) The compressed data is then decoded to be displayed on screen.

    In theory for the SD channels it may not make a huge difference if the signals are decoded by an external box or internally by the TV if a good quality video connection is used. For HD though most of the connection options available like SCART or Composite video on phono sockets can't handle HD resolutions so that will have a noticeable effect on the picture.
  • N.DeanN.Dean Posts: 1,691
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    #6
    This is like the discussion about on-screen versus on-paper books. Book on paper are sometimes called “analogue”, but all writing is digital, because each character is one of a finite set of characters.
  • spiney2spiney2 Posts: 27,058
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    #7
    but light is photons and they are digital. I blame Newton and his silly "wave" theory of light ........
  • ToenToen Posts: 795
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    #8
    No light has a duality. Diffraction and interference can only be explained by wave theory. Photo-electric effect is explained by photon particles (quantum theory).
    This has nothing to do with a television picture but one could say it is digital because the light emitters in the screen are either on or off (dark).
  • nvingonvingo Posts: 8,619
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    #9
    The way DVB-T internal tuners were implemented on early LCD TVs was little different to a scart analogue connection anyway.
    Obviously using the framestore that the digital video information is decoded/decompressed into as the framestore from which the display panel is fed gives a much crisper image than those early IDTVs
  • [Deleted User][Deleted User] Posts: 4,856
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    #10
    Richardcoulter wrote: »
    I have a digital STB connected to an analogue CRT TV.

    A friend says that the way that this works is by the STB converting the signal into analogue so that my old TV can display the digital signals.

    Therefore, am I seeing an analogue or digital picture at the end of the process?:confused:

    Thanks.

    I have a PVR connected to my 4:3 CRT. Good picture quality, mind
  • [Deleted User][Deleted User] Posts: 435
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    #11
    Toen wrote: »
    No light has a duality. Diffraction and interference can only be explained by wave theory. Photo-electric effect is explained by photon particles (quantum theory).
    This has nothing to do with a television picture but one could say it is digital because the light emitters in the screen are either on or off (dark).

    With the most greatest respect ,twaddle!
  • ToenToen Posts: 795
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    #12
    could you explain what you mean by "twaddle". Are you questioning the physics theory or the thread in general?
  • misarmisar Posts: 3,031
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    #13
    Toen wrote: »
    could you explain what you mean by "twaddle".

    twaddle (ˈtwɒd(ə)l/)
    informal
    noun
    1.
    trivial or foolish speech or writing; nonsense.
    "he dismissed the novel as self-indulgent twaddle"
  • Toxteth O'GradyToxteth O'Grady Posts: 8,492
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    #14
    Richardcoulter wrote: »
    I also always assumed that TV's with a built in Freeview tuner would give better pictures because there is no digi box to pass through; maybe if the signal has to be turned into analogue anyway it doesn't make any difference.
    Some very early digital CRT TVs essentially had the guts of an onDigital box in the bottom of them which provided the digital tuner (and of course gave them a smart card slot).

    A housemate of mine had one and the picture quality of the digital channels wasn't as good as my Ondigital STB connected to a CRT via SCART in RGB mode. The picture quality on the integrated set did look like it was connected by composite rather than RGB
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