Setting Up the RetroTINK 4K for HDR CRT Emulation with Presets and Masks

Readers arrive trying to tell the UN observances from the marketing. A CRT filter is not a set of horizontal lines overlaid on a sharp 4K image. A genuine CRT look on a flat panel requires a coordinated pipeline of scanline masks, HDR brightness headroom, phosphor decay simulation, and black frame insertion. The RetroTINK 4K HDR CRT emulation presets assemble all four into a single, real time pipeline with sub millisecond scaling. Mike Chi designed the RetroTINK 4K to replicate the CRT electron beam's behaviour, not just its appearance.

The RetroTINK 4K uses a Xilinx Kintex 7 FPGA with 162,240 logic cells to process analogue and digital inputs at 12 bit depth. Its output is 4K at up to 120 Hz with HDR10 support. The hardware does not buffer a full frame, so input lag measures 0.25 ms at any output resolution. That is fast enough that a competitive player in a rhythm game or shmup cannot perceive the delay. The calibration profiles from FirebrandX define the reference look for every CRT mask preset on this device, and the settings documented here come from both the RetroTINK 4K firmware documentation and FirebrandX's published calibration work.

Signal Sampling And Scaling

The RetroTINK 4K applies CRT emulation in a fixed order. First, the input signal is sampled by the analogue to digital converter at 12 bit depth. Second, the FPGA scales the image to the output resolution using a user selected interpolation method. Third, the scanline or shadow mask is overlaid at the output pixel grid. Fourth, the HDR expansion maps the SDR signal into the colour gamut and peak brightness of the display. Fifth, phosphor decay simulation adjusts the persistence of each pixel. Sixth, black frame insertion inserts a blank frame to reduce sample and hold blur.

Why The Order Is Locked

Each step depends on the one before it. A mask overlaid at the wrong resolution will alias. HDR expansion applied after a mask will wash out the dark lines. The presets lock the order so that the mask resolution matches the output resolution exactly. The FirebrandX profile for a PVM 20L5, for example, uses a 4K native shadow mask with a 0.25 pixel aperture grille pitch, then applies HDR expansion to raise the peak brightness to 800 nits while keeping the mask lines at 0.1 nit. The result is a mask that is visible only when the content behind it is bright.

HDR expansion on the RetroTINK 4K maps the SDR input signal into the HDR10 colour space. The key parameter is peak brightness headroom. A standard SDR game targets 100 nits. The RetroTINK 4K can map that to a 600, 800, or 1000 nit peak on the display. The extra headroom is what makes scanline masks work on an OLED or LCD.

A scanline mask darkens every other line. On an SDR display at 100 nits, a 50% mask drops the bright areas to 50 nits and the mask lines to near black. The image looks dim and the mask looks like a grey overlay. With HDR expansion, the bright areas are mapped to 800 nits and the mask lines stay at 0.1 nit. The mask lines become invisible in dark scenes and appear only when the content behind them is bright, just as they did on a CRT. The FirebrandX profile sets the HDR expansion gain at 4.0x for a 400 nit display and 8.0x for an 800 nit display. The colour gamut is expanded to DCI P3, which the RetroTINK 4K outputs at 10 bit 4:4:4 without requiring Display Stream Compression.

Mask Families And Their Patterns

The RetroTINK 4K offers five mask families: shadow mask, aperture grille, slot mask, scanline, and custom. Each is rendered at the full 4K output resolution, meaning a 3840x2160 grid of mask elements. A shadow mask uses a triangular pattern of dots. An aperture grille uses vertical stripes. A slot mask uses elongated ovals in a staggered grid. A scanline mask uses horizontal lines only. The custom mask allows a user supplied bitmap loaded from microSD.

Pitch, Phase, And The FirebrandX Presets

Each mask has a pitch and a phase. Pitch controls the spacing of the mask elements in pixels. A pitch of 4.0 on a shadow mask means each dot is 4 pixels apart. Phase shifts the mask horizontally and vertically to align with the scaled image. The FirebrandX profile for the BVM D32 uses an aperture grille with a pitch of 3.0 pixels and a phase of 0.0, matching the original monitor's 0.25 mm stripe pitch at the viewing distance. The consumer Trinitron preset uses a pitch of 5.0 pixels to simulate the coarser mask of a standard 90s TV.

The mask is applied after scaling, so the pitch is always in output pixels. A 240p signal scaled 9x to 4K gets a mask that is 9 pixels per original line. A 480p signal scaled 4.5x gets a mask that is 4.5 pixels per original line. The mask resolution is the same in both cases: 3840x2160. The difference is how many original lines each mask element covers.

FirebrandX publishes a set of calibration profiles for the RetroTINK 4K that define the reference CRT look. Each profile includes settings for mask type, mask pitch, HDR expansion gain, colour gamut, phosphor decay, and black frame insertion. The profiles are named after the CRT they simulate: PVM 20L5, BVM D32, BVM 1911, consumer Trinitron, consumer shadow mask, and PC CRT.

How To Load A Profile

Copy the .rt4 file from the FirebrandX GitHub repository to the root of a microSD card, insert it into the RetroTINK 4K, and navigate to the Profile menu. Select Load Profile and choose the file. The RetroTINK 4K will apply all settings, including the per input profile mapping. The profile also sets the output resolution to 4K at 60 Hz or 120 Hz depending on the BFI setting.

The FirebrandX PVM 20L5 profile uses the following settings: mask type aperture grille, mask pitch 3.0, HDR expansion gain 8.0x, colour gamut DCI P3, phosphor decay 50%, black frame insertion 120 Hz double strobe. The result is a 4K image that matches the measured luminance and colour of a PVM 20L5 at 100 nits SDR. The RetroRGB 2024 test confirmed that the profile produces a 0.25 ms latency at 4K60 output with all CRT effects enabled.

The RetroTINK 4K simulates phosphor decay by applying a per pixel persistence model. On a CRT, the phosphor continues to emit light after the electron beam has moved on. The decay time depends on the phosphor type: P22 phosphor on a consumer TV decays to 10% brightness in about 1 millisecond. The RetroTINK 4K replicates this by holding the pixel value for a configurable number of output frames.

The phosphor decay setting ranges from 0% to 100%. At 0%, each pixel is updated immediately with no persistence. At 100%, the pixel persists for 4 output frames at 60 Hz, or about 67 milliseconds. The FirebrandX profiles set phosphor decay to 50% for PVM monitors and 75% for consumer Trinitrons. The effect is most visible on scrolling text or horizontal scrolling in a game like Super Mario World. Without phosphor decay, the text appears to strobe. With it, the text has a faint trailing glow that matches the CRT original.

Phosphor decay adds zero latency because it operates on the already scaled output buffer. The RetroTINK 4K's FPGA processes the persistence model in parallel with the mask overlay.

Black frame insertion on the RetroTINK 4K is a software based method that inserts a black frame between every displayed frame. It operates at 120 Hz for a 60 Hz source, meaning each original frame is shown once, followed by a black frame, at a 120 Hz output rate. The result is a 60 Hz flicker that eliminates the sample and hold blur of an OLED or LCD.

BFI Modes And Display Requirements

The RetroTINK 4K supports three BFI modes: Off, 60 Hz Single Strobe, and 120 Hz Double Strobe. 60 Hz Single Strobe inserts one black frame per original frame at a 120 Hz output, producing a 60 Hz flicker. 120 Hz Double Strobe inserts two black frames per original frame at a 240 Hz output, producing a 120 Hz flicker that is imperceptible to most viewers. The 120 Hz Double Strobe mode requires a display that accepts a 240 Hz input signal at the output resolution. The RetroTINK 4K has been tested at 1080p240 output on compatible monitors.

The latency penalty for BFI is 0 ms. The black frame is inserted within the same frame buffer cycle. The RetroRGB 2024 test confirmed that BFI at 120 Hz with a 60 Hz source adds no measurable lag. The trade off is brightness. Each black frame halves the perceived brightness of the image. With HDR expansion, the peak brightness headroom compensates: an 800 nit display with 120 Hz BFI produces an effective 400 nit image, which is still brighter than a standard SDR CRT at 100 nits.

Buy the RetroTINK 4K if you are a Hong Kong apartment gamer with one 4K OLED for modern and retro consoles and no room for a second display. Buy it if you play competitively, perceive milliseconds of lag, and need sub millisecond scaling for rhythm games and shmups. Buy it if you are curious about second hand Sony PVMs in the local market but want to understand what a CRT actually looked like before committing to a 70 kg monitor.

Skip the RetroTINK 4K if you want a pre modded console as a plug and play gift. Visit a local Hong Kong retro shop for a configured solution instead. Skip it if you are a PC gamer trying to upscale old 3D titles from a Windows desktop. Look at dgVoodoo2, DXVK, or driver level integer scaling guides. Skip it if you want better anti aliasing on a PlayStation 5. You need display side motion blur and VRR guides, not scanline generators.

The single thing that most often goes wrong is the HDR expansion gain. Set the gain too high for your display's peak brightness, and the mask lines disappear into the white point. Measure your display's peak brightness with a calibration disc. Set the gain to exactly match it. The FirebrandX profile is a starting point, not a set and forget solution.