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302 MPEG glossary
M
M
Motion estimation is a further element for reducing data used in MPEG encoding.
M
a
a
P
have been moved either by movement or by camera pan. They can then be left out in the P
a
m
I
M
t
Bit rate
M
p
m
This is different for MPEG: The amount of data available can be used differently for different
display modes. 20 MB can be 4 seconds of DVD Video or 5 minutes Internet streaming in
thumbnail format. The quality of an MPEG video is measured by the width of the created
data stream, the bit rate. This is the amount of the transmitted data per time unit; it is
s
PEG glossary
otion estimation
otion estimation also occurs in the B and P frames. The image difference that still exist
fter
prediction (view page 305) are examined. Complex algorithms are used to search for
n original occurrence of the macro block in the reference frame of each macro block of the
or B frame (these are units of 2x2 blocks specially combined for this purpose), which
nd B frame. Only the information by how far and to where the macro block has been
oved is saved instead. This vector is called the motion detector.
n the
General encoder settings (view page 298), you can specify the quality of the final
PEG video. This factor also influences the time required for encoding. The longer it takes,
he better the quality.
PEG is a format used for storage and transferring. With older formats (e.g. AVI) you could
redict that 20 seconds of movie would result in 20 MB of data. The file size is this a direct
easurement of quality.
tated in kBit/s or bit per second.
Bits, not bytes are used, since the data word width has to address the transmission
restrictions.
The file size can be calculated from the average bit rate, if its length is known:
F
F=File size BRV= BRA= t=Length in s
B
F
(
r
C
The color value of each image point consists of the color values for the primary colors red,
g
= (BRV + BRA) * t
Video bit rate Audio bit rate
lock
or almost all image file editing techniques the image is subdivided into 8 x 8 pixel blocks
image points). This should be noted if you would like to used user-defined image
esolutions (width/height), and they should always be a multiple of 8.
hroma format
reen, and blue (RGB), and for traditional and technical reasons it is transformed into one