5-wire
Far too much VGA cable, for Resolume
What it does
An FFGL effect for Resolume Arena and Avenue that models a transmission line. Everything on screen is what happens to a signal on its way down five conductors: red, green, blue, H and V.
Coax loses the square root of frequency. That's skin effect, it's why the datasheets quote dB per 100 m at a given frequency, and it has a closed-form step response, erfc(alpha over two root t), that's strictly causal with a tail hundreds of pixels long. Three things follow from that one curve, and none of them is drawn separately: the picture goes soft, a bright edge smears to the right and only to the right, and the same response is still going four hundred pixels later, which is what streaking is. A symmetric blur is the usual way to get this wrong, and it reads instantly as "blurred" rather than "long cable".
Everything else depends on where in the chain a thing joins the signal. A ghost needs a mismatch at both ends, the far end to send the signal back and the amplifier to send it forward again, so a properly back-matched amplifier kills ghosting stone dead on a line nobody terminated, and each bounce lands softer than the last because it's been down the cable twice more. Colour fringes come from three conductors of different lengths: near zero for five coaxes cut off one drum, tens of nanoseconds for a CAT5 balun, whose pairs are twisted at different rates on purpose. Crosstalk couples a neighbour's rate of change rather than its level, so it outlines edges and never tints flat colour. Hum rides on the sync conductor as well as the picture, so the bar bends the lines it crosses. And there are no controls for line jitter or a rolling frame. They're what's left when the receiver runs out of sync margin.
The main thing the plugin sets out to show is that Pre-Emphasis and Cable EQ are the same filter at opposite ends of the cable, and still not the same control. Both invert the loss and both bring the picture back. But the noise, the reflections and the crosstalk all join in between. The equaliser at the display comes after them and lifts them along with the picture, so a hundred metres equalised at the receiver is sharp and grainy. The same correction at the amplifier is sharp and clean, and pays in headroom instead, because pre-emphasis overshoots every edge into the rail. That's why a proper distribution amplifier offers both, and why the plugin ships the same run as three presets, so the difference is one click away.
The equaliser is calibrated in metres, like the knob on a real cable equaliser, so setting it for the wrong length goes wrong in the way you'd recognise. There are five cable types, from proper RGBHV coax on BNC down to a ribbon loom with no shield worth the name, and ten factory presets. Universal macOS bundle and a Windows x64 DLL.
- One cable, one filter: the soft picture and the streak behind a caption are the same square-root-of-frequency response, not two effects
- Strictly one-sided — edges smear to the right and only to the right, which is the difference between a long cable and a blur
- Ghosts derived from the impedance at both ends, landing at twice the cable's transit time and getting softer every bounce
- Pre-Emphasis at the amplifier and Cable EQ at the receiver: the same filter, and only one of them lifts the noise
- An equaliser calibrated in metres, so under- and over-equalising both look like what they are
- Five cable types — RGBHV coax, a moulded VGA lead, mini-coax, a CAT5 balun and a ribbon loom — each with its own loss, velocity, conductor skew and screening
- Per-conductor skew that fringes vertical edges, and crosstalk that outlines them without tinting flat colour
- Mains hum that bends the lines it crosses, RF ingress as a herringbone, and a noise floor the equaliser has to lift
- Sync on its own two conductors: line jitter and a rolling frame emerge from a thin sync margin rather than from sliders
- A failing DC clamp, and the sampling phase every VGA monitor has an auto-adjust button for
- Pixel Clock, because the same 30 m lead is invisible at 640x480 and a plain ghost at 1600x1200
- Ten factory presets, including the same hundred metres of cable with nothing done, fixed at the display, and fixed at the amplifier
Where it stands
Released at v0.1.4. The three point releases since changed nothing in the picture: v0.1.2 shipped a Windows installer that no longer touches the system PATH (the earlier one could overwrite it), v0.1.3 gave the effect a proper description in the field Resolume shows, and v0.1.4 only changed the name Resolume lists it under, now "SW 5-wire", so the Stoatworks plugins sit together in its browser. The cable model is checked numerically by an offline harness driving the real plugin class in a headless GL context: unit gain at DC, a strictly one-sided response that never rises with frequency, a −3 dB point that tracks the square-root law, an equaliser that's the inverse of the cable and never softer than the cable on its own (an earlier design was, and nothing flagged it), a six-pass chain that matches the C++ kernel end to end on four cables, reflections within two pixels of twice the transit time, and none at all from a back-matched amplifier. All thirty controls change the picture, and all ten presets survive a host that ignores parameter value events, which is the host Resolume actually is. Still open, and worth knowing before a show: it has never been loaded into Resolume or any other FFGL host, so the parameter declarations and the About block are unproven in a real inspector. Nothing has been built for Windows locally, only in CI, and there's no OpenFX build. The loss figures, velocity factors and CAT5 skew are the manufacturers' own, but the crosstalk, pickup and sync constants were set by eye rather than measured against a real run.
Watch it running
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