Sunday, 20 April 2014

Red faces

High Definition TV is all digital. So if you have HD footage from a TV series, actually made in HD in the first place, you should be able to see it perfectly on your TV exactly as the producer wanted it to be seen.

There really is no reason to change it. Indeed, changing it in any way is more work for the TV channel, etc. It is bad enough they slap their damn logo on the image, but why make any changes?

I am sure I have blogged, like many others, on the total stupidity of overscan on HD TVs. TV screens are made with 1920x1080 pixels for full HD to match the format, and a full HD source should put the 1920x1080 pixels from the source on to the TV one-to-one. But for some stupid, and largely historical, reason some TVs are set, by default, to scale up the image so that we see slightly less than the full width and height stretched to TV size. This makes every single pixel softer as it is a calculated value from adjacent pixels. They are quite good at it, but it is different to the original and not as clear. Make sure you always set your HD TV to show HD images correctly and turn off overscan.

But I have started to notice some serious problems with some HD channels. Notable watching NCIS on Universal HD (on Sky), the colour is adjusted. Only during the programme, not the adverts, but people have red faces. It looks shite. Watching NCIS on another channel like FOX HD is fine.

Why the hell would anyone adjust an HD programme? Why not send each pixel as is without scaling or adjusting or anything. That gives the producer the best chance of showing the viewer what they intended. Yes, TVs have adjustments, though that really is a tad unnecessary though local lighting and colours could be relevant then.

Annoying.

15 comments:

  1. Go build a boat instead...

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    1. Watching TV is rare these days, and was a brief background task while coding, as I have been since 7am...

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  3. A lot of TV stations in the USA mess with the sound too. They do some sort of compression / volume normalisation. If you have a quiet scene in a TV show they slam the volume right up so something as quiet as a pin dropping is as loud as when someone speaks a few seconds later.

    Infuriating.

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    1. Well, dynamic range compression is sometimes useful, although not always desirable. For example, when watching something late at night at low volume (so as not to wake the rest of the household), lots of dynamic range is a problem since you can't hear the quiet bits.

      Ideally they would transmit both the compressed and uncompressed soundtracks so you could choose yourself.

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  4. Don't forget colour space issues; there are three that matter here:

    Old NTSC. Thiend.s a standard that was based around phosphors available easily in the late 40s, and has trouble with red; many US sets are adjusted to make this material look good, as broadcasters didn't move away from it until the 1980s.

    BT.601. This is the standard SD colour space based on PAL/SECAM phosphors and used by virtually all non-US broadcasters for SD.

    BT.709. This is the HD colour space, and differs from BT.601 slightly, so that it's easier to generate with modern phosphors or LCD screens.

    I suspect you're watching in BT.709, but the broadcast was originated in old NTSC and treated as BT.601 by the UK end

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  5. Most TVs have a setting to disable overscan for HD sources. The mystery is why this isn't the default, and why you'd ever want to set it to anything else?

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    1. I'm told the defaults are horrendous for a reason - they look good on a shop floor. Hence 'dynamic' is default (all the colours look oversaturated and unnattural) and overscan makes the picture look bigger.

      The first thing I do on encountering a new TV is set it to natural colours and switch the overscan off :p

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  6. It Gets Worse.

    I have a computer monitor which is apparently a repurposed LCDTV design. With a 16:10 aspect ratio, that's already a little weird - broadcast content is either in 4:3 or 16:9, or letterboxed from one of those formats to whatever the source material is.

    The stupidest thing, however, is that if I turn off overscan yet connect it to an Nvidia graphics card over HDMI (the only digital input), it leaves a black border around the edge corresponding to the area that would have been hidden with overscan - in which such minor things as menu bars, scrollbars and taskbars tend to be found. There is a workaround, but it is so tedious to apply (since it has to be *re*applied every time I reinstall or upgrade the drivers) that I simply exile all of my Nvidia hardware away from it.

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  8. Just trying watching Coronation Street on ITV HD, it's probably the worst colour treatment possible.
    Lots of banding, obvious gamma compression / shifting.
    When it should be straight BT.709. Suspect they want to make it look good/natural on over saturated display in local Tesco. Obviously not on a properly calibrated display.

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  9. Surely your TV picture has been stuffed through some lossy compression anyway, hasn't it? So the hope that's you're seeing the same pixels the director/editor intended is vain...

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    1. Sure, but the lossy compression at least tries to keep it *looking* the same as before.

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  10. Hello. Not that I understood all of what you said but what I got was televisions over scan thereby creating red faces. So does that mean my NCIS collection of dvds is not faulty but my crappy Korean military exchange television is ruining my viewing experience? Cuz that would make sense.

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