Axis Q1755, Руководство пользователя

Страница: 16 / 66

16
AXIS Q1755/-E - Video & Audio
Video Stream
To avoid bandwidth problems on the network, the frame rate allowed to each viewer can be limited. Select the Unlimited
radio button to allow the highest available frame rate or select the
Limited to
... radio button and enter a value (1-30) fps in
the field.
Text Overlay Settings
Use these settings to include a text, date, and time as
overlay in the video stream. Click
for information on
available options.
Preview
For a preview of the image before saving, select video format
and
Open . When satisfied with the settings, click Save .
Audio
Check the Enable Audio box to enable audio.
Note:
The checkbox
Enable Audio Support
under
System Options > Security > Audio Support
must also be checked to
enable sound in the product. See Audio Support, on page 32
.
Configuration settings from Video & Audio > Audio Settings are displayed under Current Audio Settings . See Audio
Settings, on page 20 for more information on the audio settings.
H.264
GOV Settings
The GOV structure describes the composition of the H.264 video stream which consists of 2 image forms, I-images and
P-images. An I-image is a complete image, whereas a P-image is only the differences in the image as compared with the
previous image. The GOV length determines how many P-images are sent before the next complete I-image is sent.
Setting the GOV-length to a higher value may save some bandwidth but if there is congestion on the network, there may be
noticeable decay in the video quality. Setting the GOV-length to a lower value increases the video quality, in this case.
GOV length should not be higher than the set frame rate when using a pre-trigger buffer see Pre- and post-trigger buffers , on
page 32.
Bit Rate Control
The bit rate can be set as Variable Bit Rate (VBR) or Constant Bit Rate (CBR). VBR adjusts the bit rate according to the image
complexity, using up bandwidth for increased activity in the image, and less for lower activity in the monitored area.
CBR allows you to set a fixed
Target bit rate
that consumes a predictable amount of bandwidth. As the bit rate would usually
need to increase for increased image activity, but in this case cannot, the frame rate and image quality are affected
negatively. To partly compensate for this, it is possible to prioritize either the frame rate or the image quality whenever the bit
rate needs to be increased. Not setting a priority means the frame rate and image quality are equally affected.
Note:
To determine a reasonable bit rate, go to
Setup > Video & Audio > Video Stream > Image
. Under
Text Overlay
Settings
, check the
Include text
checkbox and enter the code
#b
in the
Include text
: field. The current bit rate will
display as a text overlay on the Live View page.
To preview the image stream while configuring the GOV settings and Bit rate control, select Open... under Preview.
Text, date
overlay
& time