Vivotek IB8360-W, Руководство пользователя

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VIVOTEK
User's Manual - 67
■ Dynamic Intra frame period
High quality motion codecs, such as H.264, utilize the redundancies between video frames to
deliver video streams at a balance of quality and bit rate.
The encoding parameters are summarized and illustrated below. The I-frames are completely
self-referential and they are largest in size. The P-frames are predicted frames. The encoder
refers to the previous I- or P-frames for redundant image information.
P I P P P P P P P P P P P P P P P P P P P I
P I P P P P P P P I P P P P P P P I
Static scene
Activities
P P P
P I P P P P P P P I P P P P P P P I
By dynamically prolonging the intervals for I-frames insertion to up to 10 seconds, the bit rates
required for streaming a video can be tremendously reduced. When streaming a video of a
static scene, the Dynamic Intra frame feature can save up to 53% of bandwidth. The amount of
bandwidth thus saved is also determined by the activities in the field of view. If activities occur
in the scene, firmware automatically shortens the I-frame insertion intervals in order to maintain
image quality. In the low light or night conditions, the sizes of P-frames tend to be enlarged due
to the noises, and hence the bandwidth saving effect is also reduced.
Streaming a typical 2MP scene normally requires 3~4Mb/s of bandwidth. With the Dynamic Intra
frame function, the bandwidth for streaming a medium-traffic scene can be reduced to 2~3Mb/s,
and during the no-traffic period of time, down to 500kb/s.
H.264 Frame Types
Dynamic Intra Frame w/
static scenes
Dynamic Intra Frame w/
activities in scenes
■
Smart stream II