Video Signals: A Field Guide
Every color display ever built is natively RGB - three electron guns, three phosphors, three subpixels - so the oldest professional signal is also the simplest: run each primary down its own wire as a raw voltage, add sync on a fourth (or hide it in the green channel: RGsB). Arcade boards, broadcast monitors, and Europe's SCART connector all spoke it fluently.
Nothing is encoded, so nothing degrades in decode: RGB on wires is the purest picture a display can receive, and studio monitors used it for exactly that reason. The price is triple the cable and triple the bandwidth - which is why broadcast never shipped it to homes, and why every other chapter in this guide is a scheme for squeezing these three channels into less wire.
Eleven ways to move a picture
Every video format ever shipped is an answer to one question: how do you get three planes of color (see Y′CbCr) down the wire you can afford? Eleven answers, in the order the industry gave them - from three raw voltages, to everything crammed onto one wire, and back out again into packets with no wire of their own.
One scanline, every format+
The stage above always draws the same 64 microseconds: one television line. Every format carves it the same way - a sync event so the display knows where the line starts, a quiet stretch of blanking inherited from CRT flyback, then the active picture. What changes across a century is only how that structure is expressed: a voltage dip, a logic pulse, a reserved code word (SDI's EAV/SAV), or a timestamp on a packet.
Learn to read one scanline and every waveform monitor, every "no signal" mystery, and every handshake failure becomes the same small set of questions: where is sync, where is the picture, and what happened to the space between.
Sync: the through-line+
Follow sync through the chapters and you follow the whole history. Composite buries it in the same voltage as the picture. Component gives it a dignified home on the Y wire. RGB either grants it its own wire, hides it on green (RGsB), or both (RGBHV - VGA's five-signal answer). SDI abolishes the pulse entirely: sync becomes the digital words EAV and SAV. And ST 2110 abolishes even those - every device disciplines itself to PTP time and sync is just arithmetic.
The pattern: sync migrates from voltage to code to clock. Each migration made chains more reliable and less inspectable with your eyes - which is why the waveform monitor gave way to the protocol analyzer.
One wire, many wires, one wire, no wire+
The chapters swing like a pendulum. RGB starts at three wires. Composite compresses to one - brilliant, lossy. Component swings back to three to escape composite's artifacts; TTL and early digital go wider still (a wire per bit). Then serialization pulls everything back to one: SDI on coax, TMDS on four pairs, and finally IP on no dedicated wire at all.
The driver each time is the same trade the Bandwidth Bucket module prices in Gb/s: wires cost money and connectors fail, but one wire must carry everything, which costs bandwidth - and bandwidth kept getting cheaper. The pendulum stopped when the wire itself stopped being dedicated.
Why analog died+
An analog signal degrades every meter it travels and every device it passes: noise adds, high frequencies roll off (softening the picture), reflections ghost, and levels drift - a 7-cable component run through a patch bay simply looked worse at the far end, and nothing could prove by how much. Every generation of analog tape copied those errors and added its own.
Digital's pitch was never "better pictures" - a clean analog signal was gorgeous. It was regeneration: a bit is re-decided at every hop, so the thousandth copy equals the first, and a marginal link fails loudly instead of gracefully. That cliff-edge behavior (perfect, then gone) replaced analog's slow fade - a trade every installer has cursed at least once.
Where they all survive+
None of these formats is truly gone. Composite hums along in legacy CCTV and RF modulators; component feeds a decade of still-installed projectors; VGA haunts equipment racks, medical gear and lecterns; TTL-style parallel logic drives every HUB75 LED wall panel; RGB lives one inch from your eyes, in the drive lines of every panel; and SDI remains the default plant interconnect while IP grows around it.
This is why a working calibrator still meets all eight: the venue with an SDI plant, the boardroom with an HDBaseT run, the archive with a component deck, the LED wall speaking parallel logic behind its processor. The formats retire; the installed base doesn't.
The calibrator's angle: every hop converts+
Real installations chain these formats: a media player over HDMI, into an HDBaseT extender, out to SDI for the plant, back to HDMI at the display. Every conversion is a place where levels shift (see Signal Range), matrices get assumed (see Y′CbCr), chroma gets resampled, and one box quietly decides it knows best. The picture that arrives is the sum of every opinion along the way.
So the rule from every module in this series applies hardest here: calibrate the chain the client actually watches, verify at the glass with a probe, and when something looks wrong, walk the signal path hop by hop before touching the display. That walk is half of what you hire us for.