Image Processing Reference
In-Depth Information
720 x 625
720 x 525
400 x 405
Figure 5-12 Common SDTV physical resolutions.
Table 5-2 enumerates some SDTV- and SIF-related resolutions. These are all taken
from manufacturers' literature and the different variants are included to indicate the dis-
parity between them. There are no clearly defined standards for this, so you should be
very careful when selecting input and output sizes in your compression software. It will
be more reliable if you specify exactly the size you want in pixels.
The sizes marked with an asterisk are considered to be canonical due to their inte-
ger relationship to the parent TV image size.
The smaller sizes are often used when compressing video for use on the Web.
They aren't the only sizes that are used but they are quoted in manufacturers' lit-
Some of these sizes are based on multiples of 720, some on 704, and some on the
base value of 768, which implies that some pixel aspect-ratio correction is hap-
pening as well.
Note that for the 1/2, 2/3, and 3/4 sizes, only the horizontal axis is scaled. The
line count remains the same.
High-Definition TV
High-definition TV (HDTV) is regularly broadcast in the United States now, and dur-
ing 2003 and 2004 there has been a resurgence of interest in this medium in Europe. What
is perceived as high definition depends on whether you are in the United States or Europe.
Historically, the earliest widespread UK broadcast TV service was delivered at 405
lines in monochrome. The United States introduced 525 lines, which was seen as superior,
and it also delivered color-TV services to consumers well before the UK. In Europe, 625-line
TV was engineered and delivered during the 1960s and color was introduced in the 1970s.
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