Cisco 3005 - VPN Concentrator - Gateway Operation Manual page 32

C I SCO SYSTEM S, IN C.
Number of B Frames
This value is the number of B frames to use between other types of frames. It can
range from 0 to 7, with 0 indicating that B frames will not be used. Note that some
decoders or system networks do not perform well when using B frames and thus
this setting should be thoroughly tested. For most applications, 0 B frames should
be used.
Perceptual Option
This setting specifies whether the codec should use conservative perceptual
optimization when encoding. Conservative perceptual optimization is a process by
which the codec attempts to identify "important" and "unimportant" regions in the
video frame. After identifying the regions of the frame, the codec will give a higher
priority to the quality of important regions, at the expense of the quality of
unimportant regions. The results of this feature will vary considerably depending on
the types of video being encoded.
Lookahead
This setting specifies the number of frames after the current frame, up to 30, that
the encoder will evaluate before encoding the current frame. Lookahead may
improve encoding efficiency.
Closed Captioning Page
Open Captions
When Open Captions is enabled, Line21 CC1 captions are decoded and rendered
on top of the incoming video. Thus, unlike 608, 708 or SAMI captioning, the
rendering of closed captions is done on top of video in the encoder instead of in the
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