ADS Technologies USBAV-708 INSTANT VIDEOMPX, Руководство пользователя

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The
Guide
105
El
ec
tro
ko
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pr
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sio
ng
ra
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Wh
a
t is
th
e E
K
G
?
Electrokompressiongraph
We saw in Bitrate mode—Multipass that after each pass of a Multipass encoding
a log file is written containing an analysis of the video encoded during the pass,
used in turn to optimize the rate-control strategy for any successive pass.
Normally the rate-control will use the information from the log file in an unbiased
fashion, lending equal weight to all frames and basing frame quantizers upon the
bitrate and frame complexity. However, the encoder itself can not conceive of the
actual content of a video as humans can, or accurately determine how the
human eye will perceive the quality of any particular sequence of video to be.
At low-bitrates it is often desirable to intentionally bias the rate-control as to raise
or lower the quality of a particular section of video. For example, when encoding
a movie in its entirety it is likely the viewer will be less concerned with the quality
of the titles than that of the movie itself. It would thus be desirable that the titles
are encoded with a higher quantizer (lower quality), and the bits freed by doing
so used to enhance the quality of the actual movie. Alternatively, where a
particular video sequence demands exceptional quality it is desirable to bias the
rate-control in such a way that a lower quantizer is selected and bits are drawn
from the remainder of the video in order to enhance the sequence.
The EKG makes this possible by
allowing the data in the log file to
be displayed and manipulated
graphically between passes,
displaying the video associated
with the data for ease of use.
The EKG offers fine tuning
unavailable in other encoding
software.
A complete description of the log
file data was covered in
Bitrate
mode—Multipass .
What is the EKG?
The Electrokompressiongraph