chroma subsampling

(redirected from color encoding)
Also found in: Wikipedia.

chroma subsampling

The reduction of color resolution in digital component video signals in order to save storage and bandwidth. The color components are compressed by sampling them at a lower rate than the brightness (luma). Although color information is discarded, human eyes are less sensitive to color than to brightness.

YCbCr Is the Digital Equivalent of YUV
The YUV color space is encoded digitally as YCbCr. The luma uses the same Y designation, but U and V become Cb and Cr (for details, see YUV).

YCbCr Is Designated as 4:n:n (Y:Cb:Cr)
The 4 is the sampling rate of the luma, and n:n represents Cb:Cr. Review the illustrations below. Each 8x8 matrix represents a "macroblock" of 64 pixels in a video frame. The pink squares are the pixel locations where the sample is taken. Sony's HDCAM uses a different notation because it compresses both the luma and the colors (see 3:1:1).


Analog or Digital?
Slightly confusing because the outputs on the back of this DVD player are analog, correctly identified as Y, Pb and Pr, not the digital Y, Cb and Cr.


4:4:4 and 4:4:4:4 (No Color Reduction)
The Cb and Cr colors are sampled at the same rate as the luma (Y). MPEG-2 supports 4:4:4 coding, but this is often considered overkill and not needed. However, when video is converted from one color space to another, it is often resampled first to 4:4:4. Four fours (4:4:4:4) adds a transparency channel (see alpha channel).


Analog or Digital?
Slightly confusing because the outputs on the back of this DVD player are analog, correctly identified as Y, Pb and Pr, not the digital Y, Cb and Cr.


4:2:2 (1/2 the Luma Samples)
Cb and Cr are sampled at half the horizontal resolution of the luma (Y). Co-sited means that Cb/Cr samples are taken at the same time as Y. Considered high quality, 4:2:2 is used in professional recording, including DV (at 50 Mbps), Digital Betacam, DVCPRO 50 and MPEG-2.


Analog or Digital?
Slightly confusing because the outputs on the back of this DVD player are analog, correctly identified as Y, Pb and Pr, not the digital Y, Cb and Cr.


4:1:1 (1/4 the Luma Samples)
Cb and Cr are sampled at one quarter the horizontal resolution. Co-sited means that Cb/Cr samples are taken at the same time as the Y, and co-sited 4:1:1 is used in DV, DVCAM and DVCPRO formats.


Analog or Digital?
Slightly confusing because the outputs on the back of this DVD player are analog, correctly identified as Y, Pb and Pr, not the digital Y, Cb and Cr.


4:2:0 (1/4 the Luma Samples)
The zero means that Cb and Cr are sampled at half the vertical resolution of Y. MPEG-1 and MPEG-2 use 4:2:0, but the samples are taken at different intervals. By the time MPEG-2 came along, it was known that 4:2:2 coding was often converted to 4:2:0, which is why MPEG-2 sampling more closely lines up with the 4:2:2 pattern. H.261/263 also uses 4:2:0.

Analog Too


Engineers use the 4:n:n nomenclature loosely to refer to relative bandwidths of analog signals. For example, if digital RGB signals in the computer are converted to analog color difference signals (YPbPr), they start out at 4:4:4 YPbPr. When filtered prior to sampling, they might be characterized as 4:2:2 YPbPr. See YPbPr, YCbCr and YUV.


Analog or Digital?
Slightly confusing because the outputs on the back of this DVD player are analog, correctly identified as Y, Pb and Pr, not the digital Y, Cb and Cr.
References in periodicals archive ?
STBs can convert both analogue and digital signals into NTSC/PAL/SECAM color encoding system.
On Friday, June 26th the Editors' Lounge will host a special evening dedicated to educating the post production community about ACES, the Academy Color Encoding System, as well as the latest in state-of-the-art, reference-grade monitors.
This delivers superior picture quality for S-video compatible equipment, such as devices that have the relevant connections and color encoding.
Beginning with the fundamentals of color and human color perception, the book progresses to in-depth analyses of the nature of color images, digital color encoding, color management systems and digital color interchange.
scene-based and appearance-based color encoding methods;
With the addition of Digital Vision's 2013 rev2 grading and mastering suite (including ACES [ST 2065-1-2012]), a non-proprietary workflow based on the Academy Color Encoding Specification, Eye CandyTM can read the ACES color space directly, de bayer realtime and work non-destructively at half float from the R3d files without rendering.
For Sony PMW-F3, F23, F35 and F65 shooters looking to maintain the full dynamic range of their images in post, Vegas Pro 12 uses OpenColorIO technology from Sony Pictures Imageworks and the Academy Color Encoding Specification (ACES) color space standard to build a comprehensive S-Log workflow solution.
Customized color encoding simplifies the graphical data presentation, allowing users to immediately pinpoint areas for attention.