Apple Final Cut Pro 7 - Manual (Page 1905)

Video formats Color recording method
1", 3/4" U-matic, 1/2", VHS, D-2, D-3 Composite
Hi-8, S-VHS Y/C (S-Video)
Betacam SP, Digital Betacam, DVD, DV, D-1, D-5 Y
′
C
B
C
R
(component)
Computer graphics and digital cinema acquisition. Although video
originates in and is displayed in this format, it is rare for tape formats
(Y
′
C
B
C
R
is used instead).
RGB
Today, almost all digital video formats are Y
′
C
B
C
R
(component). Computers typically store
image data using RGB, although many Y
′
C
B
C
R
(component) formats can now be processed
natively on the computer (such as DV).
Video Sample Rate and Bit Depth
The video sample rate of a digital video format determines how often the light intensity
of each video line is sampled.
Description Sample rate
HD video luma (Y
′
) sample rate. 74.25 MHz
HD video chroma (C
B
C
R
) sample rate. This is half of the luma sample
rate, used for 4:2:2 HD video.
37.125 MHz
Early NTSC digital video recorders sampled video at exactly four
times the frequency of the color subcarrier signal (3.58 MHz x 4).
This is the origin of the 4 in color sample ratios such as 4:2:2. 14.3 MHz
This is the sample rate for the luma (Y
′
) channel for SD digital video.
This sample rate was chosen to work with both NTSC and PAL digital
video. The 4 in 4:2:2 is now represented by this sample rate.
13.5 MHz
This is the sample rate for the color difference channels in 4:2:2
video. This is half of 13.5 MHz. 6.75 MHz
Color Sample Ratio
Color sample 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 Y
′
data
stored, only two C
R
samples and two C
B
samples are stored. By reducing the number of
chroma samples, less color detail is recorded and less bandwidth is required for storage
and transmission. Because we are less sensitive to color detail than we are to luma detail,
subsampling the chroma signal can be considered perceptually lossless. In absolute terms,
chroma subsampling can make processes like chroma keying much more difficult.
Description Sample ratio
Each R, G, and B channel, or each Y
′
, C
B
, and C
R
channel, is sampled
at the same rate. Maximum color detail is maintained.
4:4:4
1905 Appendix B Video Formats