Recovering Colo(u)r From PAL Tele-recordings

You will never see every episode of Doctor Who, and that’s not because viewing every single episode would require a few months of constant binging. Many of the tapes containing early episodes were destroyed, and of the episodes that still exist, many only live on in tele-recordings, black and white films of the original color broadcast.

Because of the high-resolution of these tele-recordings, there are remnants of the PAL color-coding signal hidden away. [W.A. Steer] has worked on PAL decoding for several years, and figured if anyone could recover the color from these tele-recordings, he could.

While the sensors in PAL video cameras are RGB, a PAL television signal is encoded as luminance, Y (R+G+B), U (Y-B), and V (Y-R). The Y is just the black and white picture, and U and V encode the amplitude of two subcarrier signals. These signals are 90 degrees out of phase with each other (thus Phase Alternating Line), and displaying them on a black and white screen reveals a fine pattern of ‘chromadots’ that can be used to extract the color.

64 thoughts on “Recovering Colo(u)r From PAL Tele-recordings

    1. There are too many facebook nitwits on HaD it seems, constantly people like [What the UK] and of those ilk making their pathetic ’emulating PC’ confrontation comments.

      So if HaD can find a way to get rid of these people, please do.

  1. Hi guys great story.

    Not too sure if you are aware (coming America), but the guy in the pictures at the top of this page is Jimmy Savillie. He is one of the uk’s most prolific sex offenders to date.

    Just thourght you should know

    1. Piss off mate, aright.

      You would not complain if the recovery was of nazi soldiers or hitler or pol pot or stalin or some such would you? Nope, because why would you since it’s about recovery of material.

      Britain is just completely hysterical and should take a note from their own history and ‘remain calm’.

      Now go to a store and see books of tony blair on sale, making him money, all nice and proper. You can pay with creditcard so the US banks get their cut too, all proper and nice.

  2. Using that color image is slightly misleading for the article (likely unintentional). That color image is actually a still taken from an existing color tape. If you look further down the page you can find the actual recovered color image. It’s amazingly close to the original but there are a few changes, especially the red box around the number 1.

  3. Don’t let HAD fool ya. The pictures shown in this post are NOT before-and-after, as most would assume by their juxtaposition. The color image on the right is from color videotape, used only as a known reference to check accuracy of color recovery from the black-and-white image on the left. The actual recovered image is somewhat less accurate.

  4. Not only is this story 6 years old but the stills used are of Jimmy Savile who it turns out abuse and raped hundreds of children , most of which were in hospital at the time.

    Old story and poor taste

  5. I would never imagined I’d see Jimmy Saville, One of the UKs most prolific paedophiles, on the front page of Hackaday.
    OK so he was a popular childrens entertainer in his day but we now know his very dark secrets.
    I’m sure there are other stock BBC footage that would be more fitting for restoration.

  6. The process has been used to re-colour (to use the British excess vowel spelling) some old episodes of Dr. Who and the pilot episode of Are You Being Served.

    There are 97 missing episodes of Dr. Who, from 26 series. Audio of all the missing episodes exists due to either separate original recordings by the BBC or by fans who recorded at home by various means.

    Some of the episodes have been reconstructed using animation, partial video or film recordings and still images.

    The BBC is still searching for any copies of episodes of all their shows prior to 1978. That’s when they finally wised up and quit destroying the original films and destroying or erasing and re-using the tapes. Many of the recovered episodes have come from film copies sent to TV stations in other countries which were then kept instead of being destroyed or returned to the BBC.

    There’s an incentive if you return a copy of a lost BBC program. You get a free DVD copy of the episode after they’ve done whatever restoration it needs and have it digitized.

  7. Errr, ntsc uses u and v enciding just as much as pal does. Phase alternating lines stands for, well, phase alternating lines : encoding of color is pretty much the same as in ntsc but the phase of the u and v signal is inverted every other line. This allows automatic calibration of the hues (no blue faces or red trees, as shown on early ntsc tv sets).

    1. NTSC encodes in YIQ, PAL in YUV. (Very similar really). The alternating phase meant that visually any path differences in the reception – which would give rise to weird tint problems (visble in NTSC) – were visually cancelled by alternating this error on alternate lines of the image.
      An improvement to the NTSC signal (sometimes called never twice the same color). Also PAL generally was 625lines 50Hz vs NTSC 425/60Hz. The PAL red phosphor (in teh CRT) was typically also slightly redder than the NTSC one which was slightly oranger.
      OH TMI…

      1. “The alternating phase meant that visually any path differences in the reception – which would give rise to weird tint problems (visible in NTSC) – were visually cancelled by alternating this error on alternate lines of the image.” Absolutely correct. Really surprised at the poor description of PAL in the original posting. Even more surprised at the image used. In very bad taste IMHO.

        1. A remarkable technical story (written well before public knowlege of Jimmie Saville’s atrocities), I wonder what techniques will be needed to find lost episodes from todays programs (such as the 4K masters of old, colourised* films that were destroyed in the recent past).

          *yes colourised – all vowels are required.

  8. PAL is called PAL, not just because of the phase difference between the colour components, but because this phase difference switches around between lines. I believe it’s this switching trick that makes the colours in PAL better than those in NTSC, since it’s then easier to extract the two original signals.

    Anyway, it’s neat if they can extract any of this information from a B&W recording!

    1. I made frame grabbers for Apple II’s in the 80’s. When I first got them working I had a B&W Sony camera. I tested color by grabbing video from the San Francisco and San Jose TV stations. Channel 7 produced the alternating dot patterns (NTSC color burst reference switches phase with each line) and channel 4 and 5 did not. I never found out why.

  9. It may not sound it after reading this, but I love America. But goddamit you people live in a bubble and have no idea what is happening on planet Eatth. A more offensive picture for an article could not have been chosen.

    1. That is a bit of a hyperbole I think. A still image from the 80’s with Saville in a weird shirt could not be more offensive than say Anne Frank’s head photoshopped into some vintage B&W German leather bondage porn?

      1. I think this article talks about BBC, that is in fact a UK establishment and not German. Also your proposed event occurred some decades before this technique described here became relevant.

    2. Since we are lumping in all of America based on one persons article, maybe we could also assume that most of planet Earth just doesn’t give a shit what goes on in the UK anymore.

  10. And while we are at it, lets never post a picture of Hitler again, that will surely rid the world of fascism.. What a bunch of knee-jerk PC bullshit.
    Perhaps erase the tele-recordings as well, because that is how we gain a complete historical record that we could learn from…

      1. And this picture is used within the context of Saville being almost omnipresent on BBC television in the 70’s and 80’s. (and also that shirt must be the ultimate litmus test for this project).

        Point is that this image is in no way defending, supporting or connected to the actions by Saville making it a non-symbol to go ape-shit-crazy over. Complaining about this is so utterly detached from the real problem and the real world that the only thing that is gained is weight to the erroneous concept that such superficial grievances actual have merit and are somehow mean something.

  11. The images are from 2008, back then Jimmy was a saint. This reminds me a bit of how some anti-smoking campaigners wanted all black and white films that showed cigarettes be edited to remove them. Or the puritans that wanted Michelangelo’s David castrated. The guy was evil, he is dead, lets move on.

    Interesting article, thanks HaD.

  12. Putting aside the image of Jimmy Savile; my understanding of how this works is nothing intrinsic in the way the PAL (AKA Picture Always Lousy) but an unintended consequence of a fudge – there was not enough bandwidth in the channel for the dominance and the luminance to be separated fully so the colour is aliased on the monochrome image. It is why the BBC avoided things like suits with narrow stripes the high frequency luminance signal was aliased onto the chrominance and gave some really trippy colour effects.

  13. It’s amazing how many people think that British local news is somehow relevant enough that every person on the planet should have full knowledge of all of it at all times.
    And people think Americans are self-centered?

    This in no way is meant to endorse that perverted pile of human filth, but please get over yourselves already.

    1. I have every Who episode in existence on a hard drive. This includes reconstructed episodes, and some audio recordings. The VLC playlist comes in at just over a month. If you don’t want to sleep, or eat, yeah, you could do it in about a month.

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