Bringing Back The CRT TV Experience In Software

Cathode-Retro is a collection of shaders and sample C++ code for reliving the glorious days when graphics were composite video signals displayed on a CRT screen. How? By faking it in software and providing more configuration options than any authentic setup ever had.

Love it or don’t, there’s nothing quite like it.

Not satisfied with creating CRT-style color images with optional scanlines and TV picture controls like tint and saturation, Cathode-Retro can emulate more nuanced elements as well.

The tool includes the ability to imitate things like the slight distortion of a period-correct curved screen, the subtle effects of different methods CRT displays used to actually work (such as shadow mask vs aperture grille), and even taking into account the slight distortion of light refracting imperfectly through the glass face of the CRT. There’s even options for adding noise and ghosting, which may spark some artistic ideas.

If all you need is software to recreate an old-school CRT terminal, we have you covered. But if your needs are a bit more low-level, Cathode-Retro might be what you’re missing.

44 thoughts on “Bringing Back The CRT TV Experience In Software

  1. Color convergence? Bringing the 3 CRT beams together in an exact point at every place on the screen is near impossible. Dynamic circuitry (magnetic coils etc) tweak the deflection of the 3 beams to get the spot as near a spot as possible over all the screen. When convergence is poor the 3 colors can be seen distinctly separate. I’d hope that the crt TV experience would include a simulation of (bad) convergence and correction.

    1. I used to repair CRTs and colour convergence wasn’t that hard. Customers used to comment on colour clarity which is ironic as I uses a different technique as I am colourblind.

      The harder thing to emulate (I have considered doing this in VHDL) is that fact that different phosphors have different persistence rates.

      Phosphors are one of the more significant differences between studio/professional monitors and consumer quality.

  2. The other day I was reminiscing about the Vertical and Horizontal Hold controls on old TVs. Modern TVs don’t need them, but it sure was nice back in the day to solve a problem so easily. 😉

      1. Not to mention purity and convergance. Convergance became far more important when people started hooking video games and computers to CRT TVs. All of a sudden, having the red, green, and blue line up perfectly at the edges and corners of the screen became far more important. People would often expect the impossible out of cheaply made color TVs.

          1. Don’t forget the little generator that produced dots and croshatches for when you were performing the convergence. I still remember how some of the convergence pots would get hot in use, then the plastic parts would crumble when you tried to turn it.

  3. I, for one, do not miss the wight of a 19″ CRT. Trinitron monitors were great, but they took up half your desk and gave you a workout if you ever had to move them. I love my 24″ 4k LCD monitor. Reminiscing is great, but thank you, modern tech for letting me see my work more clearly and saving power and weight!

    1. Honestly I missed my 19″ iiyama 1600×1200 CRT until LCDs finally advanced past 1080p.

      My current 1440p 165 Hz HDR400 Asus LCD is miles ahead of my old CRT. The 1080p 60Hz SDR screen I had in between – not so much.

  4. At last a use for 4k screens under 55″. Now if they could somehow put back the information lost when they ‘upscale and sharpen’ all the old TV shows. I saw Cheers last week in a waiting room and the opening credits were barely recognizable. Not to mention the original star trek where alternate scenes the uoscaling would decide the character had chest hair and nipples or not randomly (though maybe that was censoring?).

    Either way, bringing back the cool CRT effects is OK in my book. Makes the old games pop again.

  5. I wonder if anyone has tried to write software to emulate the whole thing. You feed it an audio file representing the rf, the software decodes it like a spice simulation and draws vectors representing the electron beam to work out which bit of the phosphor it will hit.

  6. If you want a real CRT experience, with a little effort you can find a legit TV that the owner will let you have if you can move it yourself. They are lurking in the basement, attic and disused rex room of everyone over about 70.
    My friend got one just so Duck Hunt would work. We also sourced a hanky particle board tv stand that would crush a toddler if you push it laterally. For the full experience.

    1. Not in Europe, sadly. We take everything with us when we move.
      There’s no treasure left behind in unused homes.

      In the states, furniture and equipment is rather left behind for next person who moves in, right?

      1. >In the states, furniture and equipment is rather left behind for next person who moves in, right?


        Sometimes when people get kicked out of a place they leave crap behind but in general We too take everything with us when we move.

        If you read the comment again youll see that they arent speaking of abandoned homes.
        >They are lurking in the basement, attic and disused rex room of everyone over about 70.
        They are saying Old people still have old tvs in their homes that they are often willing to part with if you do the work of hauling them away for them.

      2. “Treasure left behind” happens often in enough in Germany. Watch “Bares für Rares” with Horst Lichter some time. You’ll see people bring in stuff they found when they bought a house – stuff just left in the attic or the basement.

    2. What I meant to say is that stuff often gets thrown away here.
      The homes are smaller in general and there’s little storage space.
      Especially the old people try to down-size and prefer luxury and the latest tech.
      What you described was true in the 2000s, though.
      At this time, CRTs were stillccommon and thus considered to be still worthy.

    3. I have a friend in the broadcast biz, who had a Trinitron CRT that must have been 27 inches. Thing was HUGE (and very expensive), but he “needed it for work” — legit, since he was in charge of the broadcast hardware for the station. I think he sold it rather than move it :-)

  7. The ultimate in shadow mask TV technology was the true flat CRT. The shadow mask was heated and stretched then a glass ring was molded around its edge. When the mask cooled it was super tight and would not distort when heated by the electron beams.

    Sony got to that concept earlier with their aperture grille with wires stretched vertically in a semi-cylindrical frame, with the radius matching the distance to the beam emitter so focus didn’t matter for horizontal sweep, just vertical scanning.

    Dot triad “spherical” CRTs always had the sharpest, best detailed image but were less bright and printing the three phosphors dots with precision was tricky. Shadow masks had to be designed to warp *into* alignment when at operating temperature.

    When the Trinitron design simplified the phosphor printing with vertical stripes, the rest of the industry answered with the slot mask. Same stripes but on a “spherical” tube and shadow mask that had vertically staggered columns of rectangular holes, each one covering a 3 color section VS the old dot triad method of a 1 to 1 mask hole to R, G, or B phosphor dot. Slot mask was much brighter than dot triad, but the chunky rectangles made for a less crisp image. Dot triad held on for a while in higher end, high resolution computer monitors.

    It’s a shame nobody made a wide screen, true flat, 1080p dot triad CRT. Would have blown away the same size plasma or LCD in image sharpness. The TV buyers had to settle for the ‘screen door’ look of slot mask or Sony’s lack of vertical definition due to bleeding up and down the phosphor stripes in their Trinitron and WEGA CRTs.

    I remember first seeing slot mask CRTs on video arcade games. I thought it was a neat way to get a brighter image but it didn’t look anywhere near as good as the late 60’s vintage 25″ dot triad TV at home.

  8. What I want to say is that things are often thrown away here.
    Homes are generally smaller and there is little storage space.
    Especially older people who try to save money and prefer luxury and the latest technology.
    What you describe actually happened in the 2000s.

  9. I pushed the boat out some years back and bought a Toshiba 40″ rear projection set. Was I proud of that! However, the basic user-adjustable convergence wasn’t great. I found out that there was a “secret” maintenance code, which was a combination of handset and TV buttons that produced a much more accurate cross-hatch pattern and, after the requisite tweaks, this made for a cracking picture, for the time – far better than when it was delivered. Of course, tech. has now moved on, but it was good in its day, after my “adjustments”.

  10. If you guys want the crt look for your retro games check out RetroArch crt shaders, better yet go on youtube and search up Retro Crisis videos that shows off what those crt shaders do and how they give old games that classic retro look as if you were playing on a old TV again.

    1. It’s technically possible, if LCD monitors based on CCD technology were around.
      CCD is sequentially operated, close to being “line based” like a CRT TV.

      And since old game consoles use 240p/288p, they may not use traditional interlacing, but limit themselves to using one of two fields.

      That’s important, because recreating interlacing with non-CRT technology is a timing sensitive tasks (CCD is slow).

  11. The two biggest problems with old games on HD flat-screens is poor upscaling and the way flat-screens update in whole frames instead of line by line. Neither of which is solved with shades.

    CRTS can switch res so no scaling is necessary. LCD and Oled need to scale all those 224p, 240p, 256p etc games to 1080p or 2160p creating an awful image with jaggies a major loss of fine details and lag.

    Updating in whole frames instead of line by line causes motion blur and lag. And… light guns no longer work.

    The first problem could be solved with a high quality upscaler. But if anyone creates an OLED that updated line by line like a CRT it would be the best gaming monitor ever created.

    1. The Audio “RF” is about 5 MHz wide.
      A modern day x86 (which isn’t x86) or x64 doesn’t actually do the GHz claimed.

      I’m not saying this isn’t doable, it is doable but you need to find someone that can code at a grass roots level, even perhaps GPU programming so like the best of the game engine developers (which are usually significantly sized teams).

      I cold try it in FPGA/SRAM if I had time as it’s much easier as a parallel process because even though the emulated appearance is sequential, you’re still pumping out the pixels at the original rate for the monitor.

      FPGA eliminates the not enough MHz issue you get with CPUs.

  12. Reading this i am thinking back to my adventures with crt projection. First projector fully analog, 480 lines or something, about 100 potentiometers to set the picture. Each tube had its own geometry settings. Almost each setting had its effects on other settings.

    Not long after that an “old” Barco data 801. 720P capable and digital chassis. In the end an Barco Graphics 808S with near mint tubes, 150mhz pixel clock, color filtering in the lenses, if i am correct 25 or 50 digital point convergence, it was a beauty in Start/mid 2000s where full HD was still on DVHS or usenet downloads. This “tube” projector long dominated over digital lcd and later dlp displaying 1080P60Hz with immense contrast and pixel perfect (i pixels, line perfect..) display and so sharp you could see the grain from the fosfor in the screen if you looked very close.

    80kgs or something in the Living room suspended on the ceiling, tinkering with hardware settings (focus, toe-in, multiple adjustments on lenses and more) but also pcb and component swapping (150mhz neck boards instead of 120) and lots….lots of tinkering with video settings, proch settings, colour calibrations and best of all… heating needed in the room :-)

    After moving to a new house no more beast at the ceiling and eventually went for an big screen TV. Just turn it in with the remote, no “warm up” times, multiple PC’s (scaler, htpc), fan noise, fault finding, hv shock because of an old/leaking lead, parts sourcing, just zap…and a nice picture.

    Thinking back, i kind of mis it :-)

  13. The past couple of weeks I’ve been reincarnating an old console tv as a modern flat-screen (basically getting rid of 70 pounds of guts), so this conversation about emulating the original CRT is fascinating.

    1. I thought FPGA and *RAM would be better because then you can also emulate the different persistence rates of different phosphors by tracking and changing the intensity of each pixel in RAM even though the output frame rate is much higher.

      On problem with the up-scaling is the beam (higher intensity spot) is a larger number of pixels on the LCD.

      As for light guns, there were two methods, one was detection the position of the beam and another was to very quickly flash different areas of the screen and the second method will still work but has a lower resolution.

      This can probably be done in FPGA for any device or a GPU for PC Game emulation.

      So called “filters” are just static and I have some in some emulators but really they don’t look authentic because of the persistence issue. I remember in Galaxian, one of the three colours of the yellow enemy used to streak on some CRTs where the brightness was too high.

      But I’m not a purist and envoy these games from time to time on a LCD.

      I am a member of a FB group dedicated to CRT users (for games) as I can repair them.

    1. That looks nice and all but it’s far from reality.

      Firstly the characteristics of a CRT that make it look like a CRT are dynamic that the phosphors had different brightness and illumination rates and that was highly noticeable with the perceived movement of games.

      Next is the aperture grill. In the example you have given the aperture grill matches perfectly with computer output resolution and that was simply impossible. No amount of trying to fine tune the two different technologies could achieve that and the fact that they were different resolutions and misaligned was actually a characteristic that made a CRT look like CRT.

      The aperture grilles gad the same number of slots per inch for different screen sizes so smaller CRTs had less slots and larger CRTs more slots while the games output resolution didn’t change. So the same game would look different on different screens sizes.

      In the end this was the limiting factor because as computer resolutions increased the apertures became more visible because they were designed for an analogue signal and NOT pixels. So we had smaller apertures but in most cases by the VGA ear a computer monitor had far less apertures than the higher resolutions it was “capable” of and there was no point in attempting to align the screen geometry so that the apertures aligned with pixels. Monitors weren’t stable and even a change in temperature would misalign it if it were at all possible in the first place.

      Really, what made CRTs look like CRTs is their imperfections as a digital monitor because they were designed for an analogue picture.

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