VIVOTEK
User's Manual - 64
■ Frame size
You can set up different video resolution for different viewing devices. For example, set a smaller
frame size and lower bit rate for remote viewing on mobile phones and a larger video size and a higher
bit rate for live viewing on web browsers. Note that a larger frame size takes up more bandwidth.
■ Maximum frame rate
This limits the maximum refresh frame rate per second. Set the frame rate higher for smoother video
quality and for recognizing moving objects in the field of view.
If the power line frequency is set to 50Hz, the frame rates are selectable at 1fps, 2fps, 3fps, 5fps, 8fps,
10fps, 15fps, 20fps, 25fps, 30fps, 40fps, 45fps, and 50fps. If the power line frequency is set to 60Hz,
the frame rates are selectable at 1fps, 2fps, 3fps, 5fps, 8fps, 10fps, 15fps, 20fps, 25fps, 30fps, 40fps,
45fps, 50fps, 55fps, and 60fps. You can also select
Customize
and manually enter a value.
■ Intra frame period
Determine how often for firmware to plant an I frame. The shorter the duration, the more likely you
will get better video quality, but at the cost of higher network bandwidth consumption. Select the intra
frame period from the following durations: 1/4 second, 1/2 second, 1 second, 2 seconds, 3 seconds,
and 4 seconds.
►Dynamic Intra frame period
High quality motion codecs, such as H.265, 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 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.264/265 Frame Types
■
Smart stream II
