Because the NTSC color television standard relies on the absolute phase of the color information, color errors occur when the phase of the video signal is altered between source and receiver, or due to non linearities in electronics. To correct for phase errors, a tint control is provided on NTSC television sets, which allows the user to manually adjust the phase relationship between the color information in the video and the reference for decoding the color information, known as the "color burst", so that correct colors may be displayed.
The tint control is normally set by sight to create satisfactory skin tones in a picture. The range of adjustment typically allows these colors to be adjusted from a green to a magenta tint. Television sets produced in recent decades typically include a (sometimes non-defeatable) distortion of the color decoding spectrum, to minimize the visual effects of phase error and lessen the need to adjust the tint control.
On broadcast equipment, such as timebase correctors and studio monitors, this control is typically marked "phase," as it adjusts the phase of the color signal with respect to the color burst signal.
Since the problem of phase errors in the real world became well known after the introduction of NTSC, the later PAL and SECAM color television standards attempted to correct for them. PAL uses the same color modulation scheme as NTSC but averages the received color information over adjacent scan lines, resulting in reduced color detail but canceling out small to moderate phase errors. (Severe phase errors result in picture grain and loss of color saturation in the PAL scheme.) SECAM uses a different modulation scheme that does not rely on the phase of the color signal. Because of this the amplitude of the color signal (color saturation) is unaffected as well. Because SECAM only broadcasts half the color information on each line, the color resolution is halved just like in the PAL system. Most TV sets designed for these later standards lack tint controls, as PAL and SECAM are not supposed to experience the problems a tint control would correct. (This leaves the viewer unable to correct for color errors originating at the transmission site, however.) Multistandard sets have tint controls for NTSC viewing, but the controls are inoperative when watching PAL or SECAM signals.
Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog signal.
Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal. Chrominance is usually represented as two color-difference components: U = B′ − Y′ (blue − luma) and V = R′ − Y′ (red − luma). Each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard.
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC) in 1941. In 1961, it was assigned the designation System M.
Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields per second, and associated with CCIR analogue broadcast television systems B, D, G, H, I or K. The articles on analog broadcast television systems further describe frame rates, image resolution, and audio modulation.
SECAM, also written SÉCAM, is an analog color television system that was used in France, some parts of Europe and Africa, and Russia. It was one of three major analog color television standards, the others being PAL and NTSC. This page primarily discusses the SECAM colour encoding system. The articles on broadcast television systems and analog television further describe frame rates, image resolution, and audio modulation. SECAM video is composite video because the luminance and chrominance are transmitted together as one signal.
Colorburst is an analog video, composite video signal generated by a video-signal generator used to keep the chrominance subcarrier synchronized in a color television signal. By synchronizing an oscillator with the colorburst at the back porch (beginning) of each scan line, a television receiver is able to restore the suppressed carrier of the chrominance (color) signals, and in turn decode the color information. The most common use of colorburst is to genlock equipment together as a common reference with a vision mixer in a television studio using a multi-camera setup.
Composite video is an analog video signal format that carries standard-definition video as a single channel. Video information is encoded on one channel, unlike the higher-quality S-Video and the even higher-quality component video. In all of these video formats, audio is carried on a separate connection.
SMPTE timecode is a set of cooperating standards to label individual frames of video or film with a timecode. The system is defined by the Society of Motion Picture and Television Engineers in the SMPTE 12M specification. SMPTE revised the standard in 2008, turning it into a two-part document: SMPTE 12M-1 and SMPTE 12M-2, including new explanations and clarifications.
A test card, also known as a test pattern or start-up/closedown test, is a television test signal, typically broadcast at times when the transmitter is active but no program is being broadcast.
Hanover bars, in one of the PAL television video formats, are an undesirable visual artifact in the reception of a television image. The name refers to the city of Hannover, in which the PAL system developer Telefunken Fernseh und Rundfunk GmbH was located.
SMPTE color bars are a television test pattern used where the NTSC video standard is utilized, including countries in North America. The Society of Motion Picture and Television Engineers (SMPTE) refers to the pattern as Engineering Guideline (EG) 1-1990. Its components are a known standard, and created by test pattern generators. Comparing it as received to the known standard gives video engineers an indication of how an NTSC video signal has been altered by recording or transmission and what adjustments must be made to bring it back to specification. It is also used for setting a television monitor or receiver to reproduce NTSC chrominance and luminance information correctly.
Broadcasttelevision systems are the encoding or formatting systems for the transmission and reception of terrestrial television signals.
In telecommunications, a pilot signal is a signal, usually a single frequency, transmitted over a communications system for supervisory, control, equalization, continuity, synchronization, or reference purposes.
A Vectorscope is a special type of oscilloscope used in both audio and video applications. Whereas an oscilloscope or waveform monitor normally displays a plot of signal vs. time, a vectorscope displays an X-Y plot of two signals, which can reveal details about the relationship between these two signals. Vectorscopes are highly similar in operation to oscilloscopes operated in X-Y mode; however those used in video applications have specialized graticules, and accept standard television or video signals as input.
Time base correction (TBC) is a technique to reduce or eliminate errors caused by mechanical instability present in analog recordings on mechanical media.
Television standards conversion is the process of changing a television transmission or recording from one video system to another. Converting video between different numbers of lines, frame rates, and color models in video pictures is a complex technical problem. However, the international exchange of television programming makes standards conversion necessary so that video may be viewed in another nation with a differing standard. Typically video is fed into video standards converter which produces a copy according to a different video standard. One of the most common conversions is between the NTSC and PAL standards.
Differential gain is a kind of linearity distortion which affects the color saturation in TV broadcasting.
The color killer is an electronic stage in color TV receiver sets which acts as a cutting circuit to cut off color processing when the TV set receives a monochrome signal.
This glossary defines terms that are used in the document "Defining Video Quality Requirements: A Guide for Public Safety", developed by the Video Quality in Public Safety (VQIPS) Working Group. It contains terminology and explanations of concepts relevant to the video industry. The purpose of the glossary is to inform the reader of commonly used vocabulary terms in the video domain. This glossary was compiled from various industry sources.
Composite artifact colors is a designation commonly used to address several graphic modes of some 1970s and 1980s home computers. With some machines, when connected to an NTSC TV or monitor over composite video outputs, the video signal encoding allowed for extra colors to be displayed, by manipulating the pixel position on screen, not being limited by each machine's hardware color palette.