CRT:Video Cables: Difference between revisions
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Revision as of 07:40, 26 February 2022
Interface (signal scheme/protocol) can vary regardless of the connector type.
Connectors
If you are looking for high quality pre-made cables that output to a specific connector, generally RetroGamingCables or Retro Access are the best options.
SCART to BNC
- Female SCART
- Male SCART
- If you want a SCART switch that supports audio out:
SCART to RCA
BNC to RCA
DIY
- If you are great at soldering, one option is to buy a console-specific video port from Console5 and replace the end of an Xbox 360 component cable with it. These are well shielded RCA cables that can carry RGBS plus audio left/right and you can adapt them to BNC with a balun.
Impedance Matching Balun
- F-type 75 Ohm to Twin-lead 300 Ohm
- (can be used in both directions)
Switches
A list of switches can be found on the FAQ page.
Interfaces
Most of the following information here is for 15KHz displays (240p/480i only) and not for 31KHz+ displays (480p+).
RGB
3, 4, or 5 channels. Usually 3, 4, or 5 BNC or 1 SCART.
RGB (or RVB in France) is a shorthand for one of the following:
| Acronym | Channels | Description | Supported Consoles |
|---|---|---|---|
| RGsB | 3 | Sync on Green (SoG) | PlayStation 2 |
| RGBS (Composite Sync) | 4 | RGB with Composite Sync (CSYNC) signal | Mega Drive / Genesis 1 & 2, SNES (NTSC), Neo Geo AES, Jaguar, Saturn, and PlayStation (with small mod) |
| RGBS (Sync on Luma) | 4 | RGB with Luma as the sync signal | PlayStation, PlayStation 2, Dreamcast, N64, Xbox, SNES |
| RGBcvS* | 4 | CSYNC over composite video (composite video Sync). Also known as “sync on composite” | Xbox, PlayStation, SNES (PAL), Saturn (PAL), and GameCube (PAL) |
| RGBHV | 5 | Independent sync (horizontal & vertical) | Dreamcast |
- Like RGBS, but sync is taken from a full composite signal. It’s a quick and dirty solution, and common.
For consoles which output a CSYNC over composite video, a sync stripper cable or module can be added to filter out the chroma/luma from Composite video and leave just the HV composite sync. See Sync Blaster at (retrogamingcables.co.uk). Similarly, CSYNC can be stripped from luma and routed to the CSYNC pin of the video port.
The difference between the sync separation types is often not noticeable, but the more separation the less chance of interference. Choose the most separated option which your equipment supports (depending on cable availability).
Component
3 channels. Usually in 3 RCA cables. Also known as YUV and YPbPr.
“Y” transmits brightness information (Luma) and CSYNC, “U” & “V” transmit colour information (Chroma).
Component is a very high quality video signal derived from RGB. Transmission bandwidth (and storage) is reduced by a large margin via exploiting the limitations of human vision and relationships between colour attributes to its advantage. The formulae for deriving the weighted signals are as follows:
Y = 0.3R + 0.59G + 0.11B U = 0.493(B - Y) V = 0.877(R - Y)
Green information is not sent as it can be derived from these relationships.
There is also a similar YCbCr, but this is a digitally encoded signal.
- Supported by: Xbox, GameCube, PlayStation 2, PlayStation 3, Xbox 360, Wii. HD Retrovision cables perform conversion of RGB to Component.
S-Video
2 channels. Usually as a 4-pin connector cable: 2 ground, 1 Chroma, 1 Luma & CSYNC.
S-Video is derived from component video where Y retains the same level of fidelity along with synchronization signals, but the U & V signals are quadrature modulated and sent as one signal down the second wire.
S-video is considered a higher quality signal and is well supported by hardware from the mid 1990s and later.
- Supported by: SNES, PlayStation, PlayStation 2, Dreamcast, N64, Xbox, Phillips CDi.
- Easily Modded Consoles: Master System, Genesis, 32X, SNES Mini
Composite
1 channel. Usually one RCA.
Composite, as the name implies, is a complex signal. It was designed for NTSC, PAL, and SECAM broadcasting and contains the information for hue and saturation (together chrominance), luminance, horizontal, and vertical sync all in one channel. That’s 5 distinct video signals mixed into one wire. This does not contain audio.
While it is often downplayed as inferior to other video signal types, it remained a standard for which many CRTs and game consoles were designed to handle. The quirks and lossiness of the signal were sometimes exploited in games to create useful effects such as smoothed colour dithering and fake transparency. Examples here on Genesis and SNES (nerdlypleasures.blogspot.ca) and here with the transparent tubes in Sonic 2 (youtube.com). On the other hand, visual defects such as dot crawl and jitter can be a real nuisance of interference between the 5 signals. Many consumer TVs have a "comb filter" designed to eliminate interference issues, but often times professional or broadcast monitors do not have a comb filter as studios often wanted to be able to see interference issues and eliminate them during broadcast.
Composite supports up to 480i resolution in NTSC and 576i in PAL.
RF
1 channel. Usually F-type coax, sometimes RCA, sometimes twin-lead.
RF (Radio Frequency) is a Frequency Modulated signal in the UHF band usually incoming from an antenna or long run cable. This signal contains modulated composite video and mono/stereo audio. It does a great job of transmitting a signal over very long distances over air or wire with little loss.
Most televisions feature an RF tuner and demodulator to handle RF input. The most common connector is the F-type (coax, like cable TV). Much older televisions (early 1980s and earlier) usually have two screws to fasten down a twin-lead antenna. Rarely they will have an RCA-type connector which expects RF input. Televisions with a rotary select dial usually indicates that it only supports RF input. Depending on the television, the RF tuner is usually connected to all inputs and may be designed to handle both 300 Ohm and 75 Ohm. The F-type connector is almost always expecting 75 Ohm input. Check the TV user guide or service manual to be sure. It will not harm the television to feed the wrong impedance, but the signal may be too weak to see.
If the impedance from your console to the TV is mismatched, you need a balun (transformer) – a very simple circuit and cheap to buy for less than $5 USD.
Comparison
RF is merely FM encoded Composite plus audio for long run transmission. It is prone to heavy interference from external RF signals.
Composite is a complex signal for simple transmission of light and colour information, which partly suffers by design (limited colour fidelity) and partly by interference due to transmission and reception equipment quality.
S-Video is a big step up in quality over Composite. By merely separating the signals to two wires, most of the problems we see with Composite are eliminated.
Component (YPbPr) is where very high fidelity comes into play. Slight differences may be noticeable only when compared directly to the original, and only really depends on the particular hardware used.
RGB is the original signal.