Manual
1038 Part XIII Appendixes
Color Sampling Ratio
Color sampling ratio refers to the ratio of luma (Y) samples to each color difference
sample (C
B
and C
R
). For example, 4:2:2 color sampling means that for every four pixels
of luma information stored, only two C
R
samples and two C
B
samples are stored. By
reducing the number of chroma samples, less information is recorded. This is usually
acceptable because the luma signal contains more of the detail our eyes see, so the
chroma signal doesn’t need to be stored as accurately.
The following table shows a list of color sampling used in various digital video formats:
Sampling ratio Description
4:4:4 Each R, G, and B channel, or each Y´, C
B
and C
R
channel, is sampled,
and no samples are skipped. There are almost no tape formats that
record with this color sampling ratio.
4:4:4:4 Full sampling rate for each color channel, plus a fourth alpha
channel.
4:2:2 Every other chroma sample is skipped, so the color resolution is
halved. For example, the first pixel in a line contains Y´, C
B
and C
R
samples. The next pixel contains only a Y´ sample. This pattern
repeats. Most professional video formats use 4:2:2 color sampling.
4:2:2:4 4:2:2 sampling rate for each color channel, plus an alpha channel at
the full sampling rate.
4:1:1 Only one of every four chroma samples is recorded, so the color
resolution is quartered. The first pixel in a line contains Y´, C
B
and C
R
samples. The next three pixels only contain Y´ samples. This pattern
repeats.
4:2:0 This ratio has a different meaning than the others. This does not
mean that there are 2 C
R
samples and 0 C
B
samples. Instead, on
one line, there are two C
R
samples for every four Y´ samples., but
no C
B
samples. On the next line, there are two C
B
samples for every
four Y´ samples, but no C
R
samples. This pattern repeats. Therefore,
each line contains only C
R
or C
B
samples, but not both.
Sampling ratio Video formats
4:4:4 HDCAM SR
(Few video formats record this format because so much data
is required.)
4:2:2 Digital Betacam, D-1, D-5, DVCPRO HD, DVCPRO 50
3:1:1 HDCAM
4:1:1 NTSC DV, NTSC DVCAM, and DVCPRO
4:2:0 PAL DV, PAL DVCAM, and HDV