colour subcarrier BrE
color subcarrier AmE

The use of the colour subcarrier means the signals sometimes appear as blue and yellow patterns on a regular PAL TV set.

For example analog television systems transmit a burst of the transmitting colour subcarrier after each horizontal synchronization pulse for reference.

The PAL-M system has a different sound carrier and a different colour subcarrier, and does not use 625 lines or 50 frames/second.

PAL-M is incompatible with 625-line based versions of PAL, because its frame rate, scan line, colour subcarrier and sound carrier specifications are different.

One out of every 4 lines of the high-pass result is then hidden in the remaining 144 black lines at the top and bottom of the picture, using the U colour subcarrier.

Thus, the chrominance (colour) signal is typically 'shoe-horned' into the same channel as the luminance (brightness) signal, modulated on a fixed frequency, known as the colour subcarrier.

The PAL-N system has a different sound carrier, and also a different colour subcarrier, and decoding on incompatible PAL systems results in a black and white image without sound.

This colour burst is not actually in phase with the original colour subcarrier, but leads it by 45 degrees on the odd lines and lags it by 45 degrees on the even lines.

Both luminance and chrominance information in composite video therefore have to be low-pass filtered else crosstalk between high-frequency luminance information and the colour subcarrier will lead to unwanted video artifacts patterning when viewed.

It's not identical to PAL-M and incompatible with it, because the colour subcarrier is at a different frequency; it will therefore display in monochrome on PAL-M and NTSC television sets.

In order that the phase of this locally generated signal can match the transmitted information, a 10 cycle burst of colour subcarrier is added to the video signal shortly after the line sync pulse, but before the picture information, during the so-called back porch.

Like D-2, the composite video signal is sampled at four times the color subcarrier frequency, with eight bits per sample.

( In color TV depending on the system used, superimposed color subcarrier may have slightly higher values. )

These are used to ensure that the television receiver is properly demodulating the 3.58 MHz color subcarrier portion of the signal.

The higher resolution was a necessary consequence of the higher frequency of the PAL color subcarrier.

Many analog videotape systems rely on a downconverted color subcarrier in order to record color information in their limited bandwidth.

The use of the colour subcarrier means the signals sometimes appear as blue and yellow patterns on a regular PAL TV set.

For example analog television systems transmit a burst of the transmitting colour subcarrier after each horizontal synchronization pulse for reference.

(Another way this is often stated is that the color subcarrier frequency is an odd multiple of half the line frequency.)

The color burst consists of a minimum of eight cycles of the unmodulated (fixed phase and amplitude) color subcarrier.

The color subcarrier, as noted above, is 3.579545 MHz above the video carrier, and is quadrature-amplitude-modulated with a suppressed carrier.

The PAL-M system has a different sound carrier and a different colour subcarrier, and does not use 625 lines or 50 frames/second.

PAL VHS color subcarrier is similarly downconverted (but from 4.43 MHz).

PAL-M is incompatible with 625-line based versions of PAL, because its frame rate, scan line, colour subcarrier and sound carrier specifications are different.

Typically, the chrominance bandwidth is reduced in analog composite video by reducing the bandwidth of a modulated color subcarrier, and in digital systems by chroma subsampling.

(Note that neither PAL nor NTSC was itself used, the black and white version of video storage was used with no color subcarrier.)

One out of every 4 lines of the high-pass result is then hidden in the remaining 144 black lines at the top and bottom of the picture, using the U colour subcarrier.

Thus, the chrominance (colour) signal is typically 'shoe-horned' into the same channel as the luminance (brightness) signal, modulated on a fixed frequency, known as the colour subcarrier.

When the frequencies of these signals equals the frequency of the color subcarrier wave, they may create an irritating color dot pattern like confetti, which interferes with the monochrome picture.

To minimise subcarrier visibility on a monochrome receiver it was necessary to make the color subcarrier an odd multiple of half the line scan frequency, the multiple originally chosen was 495.

The modulation technique of the color subcarrier is quadrature amplitude modulation (QUAM ) both in PAL and NTSC systems.

The PAL-N system has a different sound carrier, and also a different colour subcarrier, and decoding on incompatible PAL systems results in a black and white image without sound.

This was the subcarrier frequency originally chosen, but tests showed that on some monochrome receivers an interference pattern caused by the beat between the color subcarrier and the 4.5 MHz sound intercarrier could be seen.

This colour burst is not actually in phase with the original colour subcarrier, but leads it by 45 degrees on the odd lines and lags it by 45 degrees on the even lines.

Both luminance and chrominance information in composite video therefore have to be low-pass filtered else crosstalk between high-frequency luminance information and the colour subcarrier will lead to unwanted video artifacts patterning when viewed.

In the NTSC and PAL color systems, U and V are transmitted by adding a color subcarrier to the composite video signal, and using quadrature amplitude modulation on it.