Maximize Your PS1 Picture: RGB SCART Cable Explained

Index

1. Introduction

Do you remember when you used to connect a PlayStation 1 to your old CRT television (the ones that are now so sought after and valued by the retro community)?

If we take a look at the back of a European or Japanese PlayStation 1 (there may be slight differences depending on the hardware revision), we’ll see:

  • A red RCA connector carrying the right audio channel.
  • A white RCA connector carrying the left audio channel.
  • A yellow RCA connector carrying the composite video signal.
  • And a Multi-AV output connector.

Figure 1. PlayStation 1 rear view.

The PlayStation 1 was bundled with a Multi-AV to RCA cable (Figure 2). Red and white carry the right and left audio channels, and yellow RCA carries the composite video signal.

Figure 2. Multi-AV to audio and composite video RCA connectors.

The composite video (CVBS) signal is “all-in-one,” meaning it contains luminance (Y), chrominance (C), and sync information:

  • Luminance defines the brightness level and black-and-white detail.
  • Chrominance represents the color, modulated at a certain frequency and superimposed on the luminance signal.
  • Finally, the sync signal includes horizontal and vertical pulses that mark the start of each line and each frame.

A good explanation of how composite video works can be found here:

https://www.analog.com/en/resources/technical-articles/basics-of-analog-video.html

Still, here's a summary in my own words of what I've understood.

2. CVBS basic functionality

I must confess this is the first time I more or less understand how this type of video output actually works. When I used to play with my PlayStation 1, I was way too young to grasp any of this (and didn't care to), but only now have I had the need to look it up.

Figure 3 shows a monitor being scanned from top to bottom. Each scanned line is called a scan line (surprise).

Figure 3. Diagram of a monitor with scan lines. Image taken from Analog explanation.

Each scan line has the structure shown in Figure 4. The decoding system knows that a new line of information is about to be transmitted with the falling edge of the first sync tip. The next falling edge indicates that the line has ended. After the first sync tip comes the color burst, which is a frequency and phase reference used to decode the color information during the active video portion of the signal.

Figure 4. Structure of a scan line. Image taken from  Analog explanation.

There are two main variants:

  • NTSC (Never Twice Same Color) → 3.58 MHz
  • PAL (Phase Alternating Line) → 4.43 MHz

What follows is the active video portion of the signal. This is where the brightness and color of each “pixel” are encoded (NTSC or PAL). I’m putting “pixel” in quotes because this is an analog system, but for simplicity, each small chunk of the active video signal corresponds to what we typically think of as a pixel on the screen.

Figure 5. Luminance and chrominance modulation. Left image taken from  Analog explanation. Right signal generated with ChatGPT.

As shown in Figure 5:

  • Luminance is encoded in the amplitude of the signal (from 0 to 1V).
  • Chrominance is modulated in frequency (NTSC or PAL) and superimposed on the luminance. The NTSC or PAL subcarrier frequency determines how the color is modulated and later decoded by the TV.

Let’s do some quick math:

  • The duration of an NTSC scan line is ~63.5 µs.
  • The active portion lasts ~52.7 µs.
  • The typical digital sampling frequency is 13.5 MHz (ITU-R BT.601 standard).

Pixel calculation:

  • 52.7 µs × 13.5 MHz ≈ 710 samples.
  • The BT.601 standard rounds this to 720 active pixels per line in digital video.
  • Of those, typically only ~704 are actually visible (the rest are blanking margins).
  • This already hints at the well-known 720×480 (DVD NTSC) resolution.

But let’s see where the “480” in NTSC comes from.

When the first TV systems were designed, the refresh rate was synchronized with the mains frequency to avoid visible interference (like moving bars on screen).

  • In the US and Japan, mains frequency was (and still is) 60 Hz (59.94 Hz).
  • In Europe, it was 50 Hz.

It was also decided to use interlaced scanning. In NTSC, that means 30 interlaced frames per second, which fits with the 60 Hz refresh.

Duration of one field:

  • NTSC: 1 / 59.94 ≈ 16,683 µs

Number of lines per field:

  • NTSC: 16,683 µs / 63.5 µs ≈ 262.5 lines per field

Since one frame is made of two interlaced fields, the total is 525 lines per frame. They are split as follows:

  • ~480 visible
  • ~45 used for vertical sync, vertical blanking interval, teletext, closed captions, etc.

That's why NTSC resolution is commonly referred to as 480i (720x480). The same exercise could be repeated for PAL (50 Hz).

We could go much deeper into the subject—for example, explaining how interlaced scanning really works, how luminance and chrominance are modulated, or how the TV actually decodes the signal. But that would already fall outside the scope of this document and, honestly, I’d first need to study it properly and make sure I understand it myself.

3. Typical CVBS drawbacks

Composite video (CVBS) is convenient because it carries all the image information (luminance, chrominance, and sync) over a single wire. However, this “all-in-one” approach comes with several drawbacks that directly affect picture quality.

Since both luminance and color are encoded into the same signal, their frequency spectra overlap. One could think the luminance information frequency is very low compared to the color information (NTSC 3.58 MHz). However, luminance also contains high-frequency detail (for edges and fine patterns), which extends into the MHz range. At the same time, the chrominance signal is not a single pure tone but a modulated subcarrier with sidebands that spread around 3.58 MHz. As a result, parts of the luminance spectrum and the chrominance sidebands inevitably occupy the same frequency region.

In practice, filters are used to separate them, but because the overlap is real, the separation is never perfect, leading to visible artifacts such as dot crawl or false colors (Figure 6).

Figure 6. Dot crawl (left). Cross-color (right).

There are other drawbacks, but these two are the most significant, as they directly affect image quality.

4. How can we improve our video signal quality?

One straightforward way to achieve a cleaner and sharper image is to separate the color channels instead of mixing them into a single composite signal. Protocols such as RGB with separate sync keep the red, green, and blue channels independent and transmit synchronization information separately.

By avoiding the overlap of luminance and chrominance, this approach:

  • Preserves the full bandwidth of each color channel
  • Reduces artifacts such as dot crawl and cross-color
  • Improves overall image sharpness and color accuracy

Without diving into the technical details of how RGB + sync works, it’s enough to say that this method offers significantly better video quality compared to composite video, which is why retro enthusiasts often prefer RGB connections when available.

5. Extracting RGB and Sync from Multi-AV

Although the cable that comes with the console only provides audio and composite video through three RCA connectors, the reality is that the Multi-AV out connector exposes many more signals. Figure 7 shows the pinout of the connector.

Figure 7. PlayStation 1 Multi-AV connector pinout (Image taken from this forum).

Apart from the already mentioned composite video (pin 6), the Multi-AV connector also exposes other options: RGB (pins 11, 12, and 9), S-Video (Luma – pin 5 and Chroma – pin 7), and the two audio channels.

This is the first time the S-Video protocol appears in this article. S-Video is an improvement over composite video, since in this case the luminance (luma) plus the sync signal are carried over one wire, while the chrominance (chroma) is carried over another. This provides a sharper image than composite video, but it still does not reach the quality levels of RGB.

So, good news: the Multi-AV connector gives us access to the red, green, and blue lines. On the other hand, the bad news: it does not provide an independent sync signal.

To obtain this sync signal, we have three options.

Sync on Composite:
This is the most straightforward option. Most European domestic CRT TVs with SCART input were designed to accept RGB along with composite video as the sync signal. In practice, this means you can simply wire a Multi-AV to SCART cable using pins 11, 12, and 9 (RGB) plus pin 6 (composite video), along with GND and the usual connections. However, as you might expect, the sync will be somewhat noisy, since composite video carries not only the sync pulses but also luminance and chrominance information.

  • Compatibility: ✅ OSSC ✅ Framemeister ✅ RetroTINK ✅ CRT ✅ PVM

Sync on Luma:
This option uses the luminance (Y) signal from the S-Video output of the Multi-AV connector as the sync source. In this case, you simply wire pins 11, 12, and 9 (RGB) together with pin 5 (luma) to SCART, along with GND and the usual connections. Since the luma signal contains luminance plus sync but not chrominance, it provides a cleaner sync than composite video. This makes it a very good compromise: still simple to implement, yet more stable and less noisy than sync on composite. Some PVM do not accept Luma as sync.

  • Compatibility: ✅ OSSC ✅ Framemeister ✅ RetroTINK ✅ CRT ⚠️ PVM

Stripped Csync:
This option provides the cleanest sync signal but requires additional circuitry. Since the Multi-AV connector does not output a dedicated composite sync line, we take the composite video signal from pin 6 and pass it through a sync stripper (commonly using an LM1881). This chip removes the luminance and chrominance information, leaving only the pure sync pulses. The resulting signal is much more stable and noise-free, which makes it the preferred choice for professional monitors (such as Sony PVM/BVM) and upscalers like the OSSC or RetroTINK. However, the need for extra components makes this cable slightly more complex and expensive to build. Some RetroTINK solutions may require adjustments if sync signal is "too clean".

  • Compatibility: ✅ OSSC ✅ Framemeister ⚠️ RetroTINK ✅ CRT ✅ PVM

6. Pix3lmods RGB SCART cable

We have designed a simple PCB that allows us to create custom Multi-AV to SCART cables with RGB and sync signals. The PCB includes an input connector (pads) and an output connector (pads), to which a SCART connector is soldered. The sync in signal depends on the selected option: Sync on Composite, Sync on Luma, or Stripped Csync.

The schematic has been prepared to make the board compatible with additional systems such as PlayStation 2, Super Nintendo, and GameCube, although we have not yet validated the design for these systems.

Figure 8. Pix3lmods RGB SCART PCBA.

Finally, Figure 9 shows the cable, ready to be used.

Figure 9. Pix3lmods RGB SCART cable.

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