VIVOTEK Vivotek Automobile Electronics vc8201 Manuel D’Utilisation

Page de 203
 
 
VIVOTEK
 
62 - User's Manual
■ Intra frame period
Determine how often 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.
■ Video quality
•  Constant bit rate: A complex scene generally produces a larger file size, meaning that 
higher bandwidth will be needed for data transmission. The bandwidth utilization is 
configurable to match a selected level, resulting in mutable video quality performance. 
The bit rates are selectable at the following rates: 
20Kbps, 30Kbps, 40Kbps, 50Kbps, 64Kbps, 
128Kbps, 256Kbps, 512Kbps, 768Kbps, 1Mbps, 2Mbps, 3Mbps, 4Mbps, 6Mbps, 8Mbps, and 
16Mbps
. You can also select 
Customize and manually enter a value up to 40Mbps.
- Target bit rate
: select a bit rate from the pull-down menu. The bit rate ranges from 20kbps 
to a maximum of 16Mbps. The bit rate then becomes the Average or Upper bound bit rate 
number. The Network Camera will strive to deliver video streams around or within the bit 
rate limitation you impose.  
- Policy:
 If Frame Rate Priority is selected, the Network Camera will try to maintain 
the frame rate per second performance, while the image quality will sometimes be 
compromised. If Image quality priority is selected, the Network Camera might drop some 
video frames in order to maintain image quality.  
•  Fixed quality: On the other hand, if 
Fixed quality is selected, all frames are transmitted 
with the same quality; bandwidth utilization is therefore unpredictable. The video quality 
can be adjusted to the following settings: Medium, Standard, Good, Detailed, and 
Excellent. You can also select 
Customize and manually enter a value.  
- Maximum bit rate:
 With the guaranteed image quality, you might still want to place a bit 
rate limitation to control the size of video streams for bandwidth and storage concerns. 
The configurable bit rate starts from 1Mbps to 40Mbps.  
The Maximum bit rate setting in the Fixed quality configuration can ensure a reasonable 
and limited use of network bandwidth. For example, in low light conditions where a Fixed 
quality setting is applied, video packet sizes can tremendously increase when noises are 
produced with electrical gain.  
You may also manually enter a bit rate number by selecting the 
Customized option.