Example of U-V color plane, Y value = 0.5, represented within RGB color gamut

Animation of all the possible RGB colors in the YUV color space. Time is Y, X-axis is U and Y-axis is V. (see image above) The black square delimits the (-0.5,-0.5)-(0.5,0.5) range.

An image along with its Y, U, and V components.

The YUV model defines a color space in terms of one luma and two chrominance components. The YUV color model is used in the PAL, NTSC, and SECAM composite color video standards. Previous black-and-white systems used only luma (Y) information and color information (U and V) was added so that a black-and-white receiver would still be able to display a color picture as a normal black and white pictures. Image File history File links Download high-resolution version (800x800, 53 KB) Example of U-V colour plane; Y-value = 0. ... Image File history File links Download high-resolution version (800x800, 53 KB) Example of U-V colour plane; Y-value = 0. ... Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Image File history File links Size of this preview: 200 × 598 pixelsFull resolution (1600 × 4780 pixel, file size: 1. ... Image File history File links Size of this preview: 200 × 598 pixelsFull resolution (1600 × 4780 pixel, file size: 1. ... A comparison of different color spaces. ... As applied to video signals, luma represents the brightness in an image (the black and white or achromatic portion of the image). ... Chrominance (chroma for short) comprises the two components of a television signal that encode color information. ... Television encoding systems by nation. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... SECAM, also written SÉCAM (Séquentiel couleur à mémoire, French for Sequential Color with Memory), is an analog color television system first used in France. ...

YUV models human perception of color in a different way than the standard RGB model used in computer graphics hardware. REDIRECT RGB color model ...

Y stands for the luma component (the brightness) and U and V are the chrominance (color) components. The YPbPr color model used in analog component video and its digital version YCbCr used in digital video are more or less derived from it (Cb/Pb and Cr/Pr are deviations from grey on blue-yellow and red-cyan axes, whereas U and V are blue-luminance and red-luminance differences), and are sometimes inaccurately called "YUV". The YIQ color space used in the analog NTSC television broadcasting system is related to it, although in a more complex way. As applied to video signals, luma represents the brightness in an image (the black and white or achromatic portion of the image). ... Chrominance (chroma for short) comprises the two components of a television signal that encode color information. ... YPbPr (also referred to as YPrPb, PrPbY, and PbPrY) is a color space used in video electronics. ... Three cables, each with RCA plugs at both ends, are often used to carry analog component video Component video is a video signal that has been split into two or more components. ... A colour image and the Y, Cb and Cr elements of it. ... This article needs to be cleaned up to conform to a higher standard of quality. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ...

Mathematical derivations and formulae

YUV signals are created from an original RGB (red, green and blue) source. The weighted values of R, G, and B are added together to produce a single Y signal, representing the overall brightness, or luminance, of that spot. The U signal is then created by subtracting the Y from the blue signal of the original RGB, and then scaling; V is created by subtracting the Y from the red, and then scaling by a different factor. This can be accomplished easily with analog circuitry. REDIRECT RGB color model ... Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 625–750 nm. ... Leafy green fountain in Wattens, Austria. ... The term blue may refer to any of a number of similar colours. ...

Mathematically, the analog version of YUV can be obtained from RGB with the following relationships

The U and V components can also be explicated in the same way as Y, to obtain

It is supposed, in all the previous equations, that .

As a consequence, the range of the transformed components is given by

The inverse relationship, from YUV to RGB, is given by

Alternatively, using a matrix representation, the formulae become

There are some points regarding the RGB transformation matrix:

• The top row is identical to that of the YIQ color space
• If then . In other words, the top row coefficients sum to unity and the last two rows sum to zero.
• These formulae use the more traditional model of YUV, which is used for analog PAL equipment; digital PAL and digital NTSC HDTV do not use YUV but YCbCr.

This article needs to be cleaned up to conform to a higher standard of quality. ... Television encoding systems by nation. ... Television encoding systems by nation. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... Projection screen in a home theater, displaying a high-definition television image. ...

Numerical approximations

Prior to the development of fast SIMD floating-point processors, most digital implementations of RGB->YUV used integer math, in particular fixed-point approximations. In the following examples, the operator "a >> b" denotes an integer division by a power of two, which is equivalent to a right-shift of a by b bits.-1... In mathematics, a fixed point of a function f is an argument x such that f(x) = x; see fixed point (mathematics). ...

In 16-bit (modulo 65,535) arithmetic, we have Modular arithmetic (sometimes called modulo arithmetic, or clock arithmetic because of its use in the 24-hour clock system) is a system of arithmetic for integers, where numbers wrap around after they reach a certain value — the modulus. ...

Y = min(abs(r * 2104 + g * 4130 + b * 802 + 4096 + 131072) >> 13, 235)

U = min(abs(r * -1214 + g * -2384 + b * 3598 + 4096 + 1048576) >> 13, 240)

V = min(abs(r * 3598 + g * -3013 + b * -585 + 4096 + 1048576) >> 13, 240)

whereas, for 8 bit (modulo 255) math, we have

Y = (( ( 66 * R + 129 * G + 25 * B + 128) >> 8) + 16)

U = ( ( -38 * R - 74 * G + 112 * B + 128) >> 8) + 128

V = ( ( 112 * R - 94 * G - 18 * B + 128) >> 8) + 128

Luminance/chrominance systems in general

The primary advantages of luminance/chrominance systems such as YUV, and its relatives YIQ and YDbDr, are that they remain compatible with black and white analog television (largely due to the work of Georges Valensi). The Y channel saves nearly all the data recorded by black and white cameras, so it produces a signal suitable for reception on old monochrome displays. In this case, the U and V are simply discarded. If displaying color, all three channels are used, and the original RGB information can be decoded. This article needs to be cleaned up to conform to a higher standard of quality. ... An image along with its Y, Db, and Dr components. ... Analog television (or analogue television) encodes television and transports the picture and sound information as an analog signal, that is, by varying the amplitude and/or frequencies of the broadcast signal. ... Georges Valensi was a French telecommunications engineer who, in 1938, invented and patented a method of transmitting color images so that they could be received on both color and black & white television sets. ...

Another advantage of YUV is that some of the information can be discarded in order to reduce bandwidth. The human eye has fairly little color sensitivity: the accuracy of the brightness information of the luminance channel has far more impact on the image discerned than that of the other two. Understanding this human shortcoming, standards such as NTSC reduce the amount of data consumed by the chrominance channels considerably, leaving the eye to extrapolate much of the color. NTSC saves only 11% of the original blue and 30% of the red. The green information is usually preserved in the Y channel. Therefore, the resulting U and V signals can be substantially compressed. This article does not cite any references or sources. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ...

However, this color space conversion is lossy. When the NTSC standard was created in the 1950s this was not a real concern since the quality of the image was limited by the monitor equipment, not the compressed signal being received. However today's modern television is capable of displaying more information than is contained in these lossy signals. To keep pace with the abilities of new technology, attempts have been made to preserve more of the YUV signal while recording images, such as S-Video on VCRs. This does not cite any references or sources. ... S-Video (also known as Y/C) is a baseband analog video format offering a higher quality signal than composite video, but a lower quality than RGB and component video. ... The video cassette recorder (or VCR, less popularly video tape recorder) is a type of video tape recorder that uses removable cassettes containing magnetic tape to record audio and video from a television broadcast so it can be played back later. ...

Instead of YUV, YCbCr was used as the standard format for (digital) common video compression algorithms such as MPEG-2. Digital television and DVDs preserve their compressed video streams in the MPEG-2 format, which uses a full YCbCr color space. The professional CCIR 601 uncompressed digital video format also uses YCbCr, primarily for compatibility with previous analog video standards. This stream can be easily mixed into any output format needed. Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ... MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... Video compression refers to making a digital video signal use less data, without noticeably reducing the quality of the picture. ... MPEG-2 is a standard for the generic coding of moving pictures and associated audio information [1]. It is widely used around the world to specify the format of the digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. ... CCIR 601 is the old name of a standard published by the CCIR (now ITU-R) for encoding interlaced analogue video signals in digital form. ...

YUV is not an absolute color space. It is a way of encoding RGB information, and the actual color displayed depends on the actual RGB colorants used to display the signal. Therefore a value expressed as YUV is only predictable if standard RGB colorants are used (i.e. a fixed set of primary chromaticities, or particular set of red, green, and blue). An absolute color space is a color space in which colors are unambiguous, where they do not depend on any external factors. ...

Confusion with YCbCr

YUV is often and mistakenly used as the term for YCbCr. However, they are different formats. YUV is an analog system with scale factors different than the digital YCbCr system.[1] A colour image and the Y, Cb and Cr elements of it. ...

Types of sampling

To get a digital signal, YUV images can be sampled in several different ways; see chroma subsampling. A sample refers to a value or set of values at a point in time and/or space. ... In digital image processing, chroma subsampling is the use of lower resolution for the colour (chroma) information in an image than for the brightness (intensity or luma) information. ...

Converting from YUV to RGB

function RGB* YUV444toRGB888(Y, U, V); converts YUV format to simple RGB format and could be implemented using floating point arithmetic as:

• YUV444

 Y = 0.299R + 0.587G + 0.114B U = − 0.147R − 0.289G + 0.436B V = 0.615R − 0.515G − 0.100B 

On older, non-SIMD architectures, floating point arithmetic is much slower than using [fixed point] arithmetic, so an alternative formulation is:-1...

 C = Y - 16 D = U - 128 E = V - 128 

Using the previous coefficients and noting that clip() denotes clipping a value to the range of 0 to 255, the following formulas provide the conversion from YUV to RGB:

 R = clip(( 298 * C + 409 * E + 128) >> 8) G = clip(( 298 * C - 100 * D - 208 * E + 128) >> 8) B = clip(( 298 * C + 516 * D + 128) >> 8) 

• YUV422

INPUT: Read 4 bytes of YUV (u, y1, v, y2 ) OUTPUT: Writes 6 bytes of RGB (R, G, B, R, G, B)

 u = yuv[0]; y1 = yuv[1]; v = yuv[2]; y2 = yuv[3]; 

Using this information it could be parsed as regular YUV444 format to get 2 RGB pixels info:

 rgb1 = YUV444toRGB888(y1, u, v); rgb2 = YUV444toRGB888(y2, u, v); 

YUV422 can also be expressed in YUY2 FOURCC format code. That means 2 pixels will be defined in each macropixel (four bytes) treated in the image.
A FOURCC (literally, four character code) is a sequence of four bytes used to uniquely identify data formats. ... Image File history File links No higher resolution available. ...

• YUV411

 // Extract yuv components u = yuv[0]; y1 = yuv[1]; y2 = yuv[2]; v = yuv[3]; y3 = yuv[4]; y4 = yuv[5]; 

 rgb1 = YUV444toRGB888(y1, u, v); rgb2 = YUV444toRGB888(y2, u, v); rgb3 = YUV444toRGB888(y3, u, v); rgb4 = YUV444toRGB888(y4, u, v); 

So the result is we are getting 4 RGB pixels values (4*3 bytes) from 6 bytes. This means reducing size of transferred data to half and with quite good loss of quality.

• YUV420p (and YV12)

YUV420p is a planar format, meaning that the Y, U, and V values are grouped together instead of interspersed. The reason for this is that by grouping the U and V values together, the image becomes much more compressible. When given an array of an image in the YUV420p format, all the Y values come first, followed by all the U values, followed finally by all the V values.

The YV12 format is essentially the same as YUV420p, but it has the U and V data reversed: the Y values are followed by the V values, with the U values last. As long as care is taken to extract U and V values from the proper locations, both YUV420p and YV12 can be processed using the same algorithm.

As with most YUV formats, there are as many Y values as there are pixels. Where X equals the height multiplied by the width, the first X indices in the array are Y values that correspond to each individual pixel. However, there are only one fourth as many U and V values. The U and V values correspond to each 2 by 2 block of the image, meaning each U and V entry applies to four pixels. After the Y values, the next X/4 indices are the U values for each 2 by 2 block, and the next X/4 indices after that are the V values that also apply to each 2 by 2 block.

Translating YUV420p to RGB is a rather involved process compared to the previous formats. Taking a 16 by 16 image for example, getting the RGB values for pixel (5, 7) where (0, 0) is the top left pixel would be done as follows. The character "/" implies integer division, meaning that if there is a remainder, it will be discarded.

 Height = 16; Width = 16; YArraySize = Height * Width = 256; Y = Array[7 * Width + 5]; U = Array[(7/2) * (Width/2) + 5/2 + YArraySize]; V = Array[(7/2) * (Width/2) + 5/2 + YArraySize + YArraySize/4]; RGB = YUV444toRGB888(Y, U, V); 

As shown in the above image, the Y, U and V components in YUV420 are encoded separately in sequential blocks. A Y value is stored for every pixel, followed by a U value for each 2x2 square block of pixels, and finally a V value for each 2x2 block. Corresponding Y, U and V values are shown using the same color in the diagram above. Read line-by-line as a byte stream from a device, the Y block would be found at position 0, the U block at position x*y (6*4 = 24 in this example) and the V block at position x*y + (x*y)/4 (here, 6*4 + (6*4)/4 = 30). Image File history File links No higher resolution available. ...

Raw YCbCr streams are often stored in files with extension ".yuv". Here are some freely available examples for research purposes: http://www.tkn.tu-berlin.de/research/evalvid/cif.html. These are simply a sequence of YCbCr frames serialized into a byte stream.

See also

• Chroma subsampling
• S-Video

In digital image processing, chroma subsampling is the use of lower resolution for the colour (chroma) information in an image than for the brightness (intensity or luma) information. ... S-Video (also known as Y/C) is a baseband analog video format offering a higher quality signal than composite video, but a lower quality than RGB and component video. ... A comparison of different color spaces. ... A color model or colour model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. ... An RGB color space is any additive color space based on the RGB color model. ... A representation of additive color mixing—In CRT based (analog electronics) television three color electron guns are used to stimulate such an arrangement of phosphorescent coatings of the glass, the resultant reemission of photons providing the image seen by the eye. ... It has been suggested that process color be merged into this article or section. ... This article or section does not cite its references or sources. ... The HSL color space, also called HLS or HSI, stands for Hue, Saturation, Lightness (also Luminance or Luminosity) / Intensity. ... Mixture of RYB primary colors RYB is a historical set of subtractive primary colors. ... Without further qualification, Lab color space refers to that of Hunter (Richard S Hunter, JOSA, 38, p 661 (1948)), which is an Adams Chromatic Valance Space. ... Television encoding systems by nation. ... An image along with its Y, Db, and Dr components. ... SECAM, also written SÉCAM (Séquentiel couleur à mémoire, French for Sequential Color with Memory), is an analog color television system first used in France. ... This article needs to be cleaned up to conform to a higher standard of quality. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ...

External links

• RGB/YUV Pixel Conversion
• Explanation of many different formats in the YUV family
• Charles Poynton - Video engineering
• YUV422 to RGB using SSE/Assembly