ADS Technologies USBAV-708 INSTANT VIDEOMPX, Руководство пользователя

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Moving the slider left of center, or lowering
the modulation value, biases bandwidth in
favor of high-motion frames and
consequently away from low-motion
frames. Moving the slider right of center,
or raising the modulation value, biases
bandwidth in favor of low-motion frames
and consequently away from high-motion
frames.
When determining the most appropriate bitrate modulation it is
important to remember that quality is subjective. The optimal bitrate
modulation will vary from video to video and also upon the preference of
the viewer and their personal sensitivity to different types of artifacting.
Let us consider some examples where it is beneficial to use the bitrate
modulation control.
Consider the encoding of an action movie containing several
explosion scenes or other fast-paced action and imagine the
quality tending to degrade where there is significant motion in the
scene. Moving the bitrate modulation slider left of center towards
high motion will improve the quality consistency - the degree of
adjustment relative to the level of correction required.
Once again taking an action movie as an example, imagine
encoding at a very limited bitrate in order to create video suitable
for Internet distribution. It might be desirable to intentionally bias
bandwidth
away from fast-motion scenes. Explosion scenes and
other short fast-motion sequences may consume so much of the
total available bandwidth that they actually starve the encoder of
free bits as it encodes the majority of the video, leading to low-
motion sequences that appear disproportionately degraded.
Biasing bandwidth towards low-motion will cause the fast-motion
scenes to appear at slightly lower quality, but the quality in the
remainder of the video may appear much improved.
Consider a scenic video in which the camera is panning across a
landscape and zooming in and out but pausing for periods to show
features in detail. In this situation we might like to bias bandwidth
so that low-motion scenes receive more bits than high-motion
scenes. In this way we could enforce that the highest quality is
afforded to scenes in the video where the camera focuses on
detailed features in the landscape.
Motion complexity
Unmodulated bitrate
Bitrate modulated in favor of high-motion
Bitrate modulated in favor of low-motion
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