Instruction manual

Table Of Contents
Glossary
PIKE Technical Manual V3.1.0
248
Glossary
4:1:1 YUV4:1:1 is a color mode (see YUV).
Chroma subsampling means that a lower resolution for the color (chroma)
information in an image is used than for the brightness (intensity or luma)
information.
Because the human eye is less sensitive to color than intensity, the chroma
components of an image need not be as well defined as the luma compo-
nent, so many video systems sample the color difference channels at a
lower definition (i.e., sample frequency) than the brightness. This reduces
the overall bandwidth of the video signal without much apparent loss of
picture quality. The missing values will be interpolated or repeated from
the preceding sample for that channel.
Sampling systems and ratios: The subsampling in a video system is usually
expressed as a three part ratio. The three terms of the ratio are: the number
of brightness (luminance, luma or Y) samples, followed by the number of
samples of the two color (chroma) components: U then V, for each com-
plete sample area. For quality comparison, only the ratio between those
values is important, so 4:4:4 could easily be called 1:1:1; however, tradi-
tionally the value for brightness is always 4, with the rest of the values
scaled accordingly.
YUV4:1:1 means: chroma subsampling, the horizontal color resolution is
quartered. This is still acceptable for lower-end and consumer applications.
Uncompressed video in this format with 8-bit quantization uses 6 bytes for
every macropixel (4 pixels in a row).
4:2:2 YUV4:2:2 is a color mode (see YUV).
For detailed explanation of chroma subsampling see 4:1:1.
In YUV4:2:2 color mode each of the two color-difference channels has half
the sample rate of the brightness channel, so horizontal color resolution is
only half that of 4:4:4.
ADC ADC = analog digital converter
An analog-to-digital converter (abbreviated ADC, A/D, or A to D) is a
device that converts continuous signals to discrete digital numbers.
Typically, an ADC converts a voltage to a digital number. A digital-to-
analog converter (DAC) performs the reverse operation.
AEC AEC = auto exposure control