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Before asking this, I read the Wikipedia article. I've been confused about this for many, many years. I'd like to finally get it straightened out.

What exactly is the difference between "RGB" and "component" video? Is "RGB" a form of "component"? Is "component" like a collection name for RGB, but also some other thing, perhaps several ones?

I know what these are:

  1. RF modulator = What I used for my NES and SNES back in the day. It was quite noisy.
  2. Composite-to-SCART = What my Nintendo 64 and PlayStation had. The N64 cable could also be used on my SNES; it was backwards compatible. Much better than RF.
  3. "Pure SCART" = What my Saturn had, and which supposedly had RGB/component signals inside the cable. Very crispy picture.

I know that SCART is more of a European thing, but I've always heard of "component" and "RGB" used interchangeably. "You can get an RGB cable for better quality", "is that with composite or component video?", etc. Never any other standard within "component", like "YPbPr".

What exactly is the difference between "component" and "RGB"? Did any console ever use non-RGB "component" video?

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  • 7
    You should realize that "SCART" is just a connector, not a video standard at all - In fact, SCART can hold all nearly all relevant video standards (RGB, Component video, composite/BAS/FBAS) all on one single connector
    – tofro
    Oct 15 at 15:22
  • 4
    Reading Wikipaedia is always a mistake... en.wikipedia.org/wiki/…
    – Chenmunka
    Oct 15 at 16:01
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    This isn't very retro. All these formats are still in use, including RF modulation. Although the SCART socket seems to have passed into history.
    – Chenmunka
    Oct 15 at 16:05
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    This is very much a retrocmputing-related question; video is the primary output format of many old microcomputers and video formats are (in my experience dealing with retrocoputing fans both in person and on line) one of the largest sources of confusion in the field. People should be able to come here for any answers relating to old computers, not just answers that could apply to something else as well, because in many cases how would they even know to go look in that non-retrocomputing place, wherever that might be?
    – cjs
    Oct 15 at 23:20
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    Yes, Wikipefia does have many good articles. I just say you should take them with a pinch of salt. There is a lot of misinformation too. Use it as a guide, not as gospel.
    – Chenmunka
    Oct 16 at 7:43
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In short, analog RGB means video is sent as three signals in RGB and analog component video means video is sent as three signals in YPbPr.

The YPbPr is mainly used for transferring television video signals, while RGB is mainly used for non-television computer and graphics video signals (but exceptions to both apply).

The typical definition in video engineering is that analog component video means strictly YPbPr only. In YPbPr component video the brightness information (the Y signal) and two color difference signals (the Pb and Pr signals) are transmitted as three separate components instead of being transmitted as composite signal where they are encoded using some colour encoding method (like PAL, SECAM or NTSC).

So component video does not mean RGB, even if RGB must also be sent as three separate video components over three separate wires. That is called analog RGB video.

And yes, many consoles had component video output - it's the three RCA video connectors coloured red/green/blue, but the signals are Pb/Y/Pr. Same consoles can usually output RGB video as well with a SCART adapter.

Basically the color composite video is the YPbPr that is encoded to single signal using PAL or NTSC color encoding.

If there is only an RF signal input on the TV, it will receive the composite signal that is RF modulated as if it was coming via an antenna.

Some background about subject:

Originally TVs only had an RF input, but as they demodulate the RF into baseband composite video anyway, it was easy to add composite video input connector for external devices.

Composite signal that contains colour information has to be decoded or separated into the three components (YUV/YPbPr) which just needs to be converted into RGB for driving the CRT electron guns. To get better quality and to avoid the degradation due to colour encoding and decoding, a direct YPbPr input was added to bypass colour decoding on the TV - which still needed the conversion to RGB, but that can be considered lossless, while composite colour encodind and decoding is a lossy process which degrades quality.

For some reason (that might be that France used SECAM colour encoding which was completely different from PAL and NTSC and could not be decoded to YPbPr as easily as PAL and NTSC because SECAM also halved the color resolution vertically), European TVs started to use RGB as the external interface to avoid the colour decoding stage completely - which meant that it did not matter if it was a PAL or SECAM TV, they both can receive same RGB.

So the main difference is that SCART is an European thing and TVs with SCART can accept RGB signals that drive the three RGB electron guns directly, while for some reason some other parts of the world began to use interfaces which provided the external connection to the YPbPr section before it gets converted to RGB for the electron guns.

I can't think of a reason why it was like this, but at least the YPbPr input is compatible with monochrome video signal (just use the Y), so a separate monochrome video input was not necessary - even modern TVs that still have YPbPr input will usually use the Y signal as the monochrome or color composite signal input.

As the SCART interface has both color composite input and RGB input, it also supports monochrome video via the composite input, and even requires it for RGB sync, as the RGB has no sync information.

Most modern SCART interfaces could also accept S-Video (YC, where C is the PAL or NTSC colour-encoded PbPr signal without the Y being added) and YPbPr via the RGB pins, so SCART pins were just used as general purpose analog video input interface.

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  • Passing RGB through to the electron guns will require using three matched high-quality high-voltage amplifiers to avoid color fringing. If a set instead uses luma (Y), R-Y, and B-Y signals, it can generate a G-Y signal (the inverse of a weighted average of R-Y and B-Y) and scale up the signal voltages using use one high-quality amplifier and three lower-quality ones, whose dynamic characteristics won't need to be as well matched.
    – supercat
    Oct 15 at 17:19
  • @supercat The YPbPr signal could come from a gaming console that has to internally convert RGB to YPbPr just because people have YPbPr connectors instead of SCART. It makes no difference if the link between device and TV is RGB or YPbPr, as these usually have identical input bandwidth requirement. Even in the case it is YPbPr into the TV, the TV still needs to convert that to RGB that has to be matched in timing and thus it needs to have the same three high quality high-voltage amplifiers for the RGB electron guns.
    – Justme
    Oct 15 at 17:38
  • Bandwidth requirements for U and V (or a weighted inverted average) are typically lower than for Y, and if Y, (R-Y), (B-Y), and (G-Y) signals are delivered into the high-voltage section, they can be cheaply and easily mixed to form RGB by using resistors without requiring any further amplifier stages. Purpose-designed RGB monitors would simply use three high-quality amplifiers, but television sets--even if equipped with RGB inputs--may be able to save cost by using lower-bandwidth amplifiers for everything but Y.
    – supercat
    Oct 15 at 18:59
  • @supercat Yes, for U and V - but U and V are the low bandwidth signals either being encoded to PAL/NTSC composite or decoded from PAL/NTSC composite, so it already means your signal was low res 480i or 576i. So they are not Pb and Pr signals, which could be a result of say using 1080p gaming console which converts RGB to YPbPr. But in that sense you are correct, that many analog YPbPr systems use lower bandwidth on Pb and Pr, as for example video might be stored as YCbCr using half chroma bandwidth (4:2:2).
    – Justme
    Oct 15 at 19:32
  • "external connection to YPbPr ... I can't think of a reason why it was like this." Presumably because all consumer broadcast or recorded formats are based on luminance and two colour difference signals. Nothing natively uses RGB. So it's straightforward to generate YPbPr from signals already present in a recorder or player. One of the applications for SCART connections is for set top boxes showing subtitles or Teletext pages which can natively generate RGB signals locally.
    – Graham Nye
    Oct 19 at 21:24
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What manufacturers label as component video is one of several forms of analog RGB video, because RGB just means that the red, green, and blue color channels are transmitted separately to keep them from interfering with each other.

"Component video" is more formally known as YPbPr.

Aside from different ways of encoding the color channels, you also need horizontal and vertical synchronization information and there are multiple equally valid ways to communicate that.

VGA is another form of analog RGB video.

I haven't needed to look into this before but, according to Wikipedia's Component video page:

  • SCART typically uses a four-wire RGBS system with sync on its own line
  • Standard VGA uses a five-wire RGBHV system with horizontal and vertical sync on their own lines (Which is why you specifically need to look for monitors with Sync-on-Green support for compatibility with certain devices.)

What people consider to qualify as "RGB" can vary from group to group though. Thus why some people consider YPbPr to be a type of RGB and some people only consider RGB to refer to systems which send the color channels without encoding. (I have no idea if people in the latter group have a consistent opinion of Sync-on-Green.)

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    “[RGB is] more formally known as YPbPr.” — That's not my understanding; according to the page you linked, the ‘Y’ is luma (brightness, a specific combination of R, G, and B), and Pb and Pr are the differences between that and the B and R channels. It can be converted to/from RGB using linear combinations of channels, but it's not the same thing at all.
    – gidds
    Oct 16 at 13:01
  • @gidds What I intended to communicate is that what A/V devices label as "component video" is more formally known as YPbPr. Hence putting that sentence after a paragraph beginning with "Component video is..." I never intended to imply "RGB is..." in that part, so I'll edit to clarify.
    – ssokolow
    Oct 17 at 9:23
  • Thanks. Though I hate to quibble, but isn't YPbPr one of several possible types of component video (of which RGB is another)?
    – gidds
    Oct 17 at 22:00
  • @gidds Technically, yes. In a strictly technical sense, anything that splits apart the components into separate signals is "component video", so RGB is a subset of that... but manufacturers have co-opted the term to specifically refer to YPbPr delivered via three RCA connectors, which makes "inputs and outputs labelled 'component video'" a subset of "encoding schemes and physical specifications for RGB separation". That's why the terminology is such a mess. It's turtles all the way down as far as hazy, contradictory uses go. (Plus, of course, using R/G/B color-coding for the YPbPr connectors.)
    – ssokolow
    Oct 17 at 22:09
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TL;DR The reason it is confusing is because the transition to HD introduced new terminology for video display standards. "Component video" is for HD the popular/layperson terminology, but is essentially what was formerly called RGB in earlier computer display terminology.

When people use the term "Component video" nowadays, they are usually referring to the inputs on standard HD (720p, 1080i capable) displays and the corresponding 3-way analog video cables that connect compatible devices. These 3-way connectors are analogous to RGB with embedded sync (e.g. "sync on green"), but use the encoding that is standardized for HD - known as YPbPr. This is fundamentally the same method and quality as older RGB displays, but specific to the description of HD products and their supported resolutions. Whereas RGB might be used for everything from 240p on up to very high computer display resolutions, Component Video is for the HD specific resolutions and supporting devices.

Newer game consoles, such as the Xbox, PS2, and Wii, support Component Video output for compatibility with standard HD displays. The consoles such as the Saturn, which pre-dates the wide adoption of HD displays, support the traditional RGB instead.

Also related is the parallel transition from 4:3 aspect ratio displays to "widescreen". HD is a widescreen format. Most widescreen displays with analog inputs provided support for both RGB (usually via VGA connector) and Component Video. They also can adjust to a 4:3 aspect ratio when that makes sense for the resolution being displayed.

So, in a nutshell, consoles with analog video out moved to supporting widescreen displays and resolutions that were specified by standard HD. In so doing the consoles switched from RGB to Component Video output.

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  • Component video was used in the broadcast industry long before it was used for interconnecting consumer devices.
    – supercat
    Oct 15 at 17:22
  • @supercat You are right. Still, I don't think OP is asking about the broadcast industry, though it does provide an historical context to the term "Component video".
    – Brian H
    Oct 15 at 17:44
  • @BrianH But technically, it's component video that gets encoded to composite in a studio for TV broadcast, and inside the TV composite is decoded back to component video. So inside the TV there already is a component video interface, it's just also made externally available, to allow connecting equipment with better quality and higher resolutions which are not possible using composite.
    – Justme
    Oct 15 at 18:06
  • @Justme That is quite true, too. Still, the way the term "Component video" is popularly used by a layperson is not so technical and just means a particular type of consumer interconnect standard (at least here in N.A.).
    – Brian H
    Oct 15 at 18:43
  • @BrianH: My point is that while the interconnect only became commonplace on consumer equipment around the time DVD players were introduced, it wasn't invented for that purpose. Instead, consumer equipment merely adopted an interconnect standard which the broadcast industry had been using for decades.
    – supercat
    Oct 15 at 19:05
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Welcome to SE.Retrocomputing.

I've been confused about this for many, many years.

Me too. As other answers have discussed the technicalities of the various systems I'll focus on the confusion. I eventually came to realise there are two worlds, each ignoring the other's existence.

In Europe, part of the PAL world, we have, as you noted, the SCART connector. From its introduction in 1977 it offered composite and RGB formats with the standard being extended in the late 1980s to include S-Video. RGB is a component format but looking through some old TV manuals it is always called 'RGB', never 'component'.

In the NTSC world, including North America, the only three-component format used with consumer TV is YPbPr. There is no SCART connector and no easy access to RGB for consumer TV. S-Video exists but, as in the PAL world, is less widely used and is somewhat lower quality than a three-component format.

People in the NTSC world therefore just regard YPbPr and component as being synonymous. There are any number of articles written in the NTSC world confidently asserting that component means YPbPr without mentioning other component formats or pointing out that their claims are only valid in the NTSC TV world. (Of course there is plenty of RGB in areas using NTSC; it's just on computer monitors, either as a collection of up to 5 BNC connectors or later as VGA, but not on TVs.)

To see how pervasive this tendency is even the otherwise excellent answer here by @Justme which discusses PAL, and even SECAM, starts off by equating component video with YPbPr.

So let's have a look at your original questions:

What exactly is the difference between "RGB" and "component" video? Is "RGB" a form of "component"?

Yes, it's one form of component video. However, based on my old TV manuals and my recollections from the time, here in the UK we referred to it as RGB rather than component.

Is "component" like a collection name for RGB, but also some other thing, perhaps several ones?

It's a name for any video format where the TV picture is split across multiple signal lines. In the NTSC world the only popular component format is YPbPr. It's common for people writing in the NTSC world to regard YPbPr as the only component format, to the confusion of PAL users.

For an earlier Retrocomputing look at European TVs and monitor connections see here.

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