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3.
Setting the GOV Length
The GOV length of an H.264 stream is the sum total of I-frames and P-frames in a GOV (Group
of video images). An I-frame, or intra frame, is an image that is coded in its entirety. A P-frame,
or predictive inter frame, refers to parts of earlier images (I-frames and/or P-frames) to code the
frame and therefore uses less bits to transmit the image. Increasing the GOV length decreases
the frequency of I-frames, and therefore reduces bandwidth consumption and image quality.
To set the GOV length:
1.
2.
3.
Video Compression Settings
This section describes how to set the video quality, how to display the compression information
on the home page, and how to enable Constant Bit Rate (CBR) mode.
Setting the Video Compression
You can set the compression level (or quality) for each type of video stream: Motion JPEG,
H.264-1, and H.264-2. Higher bit rates produce higher quality images but require more
bandwidth to transmit the images.
To set the MJPEG compression:
1.
2.
Click the Save button directly below the Video Rotate Type drop-down list.
Click the Streaming tab (Video Format is selected in lefthand column).
Under GOV Settings, type a value in the H.264-1 GOV Length field and/or the H.264-2
GOV Length field.
Note
Enter a GOV Length value in the range from 2 to 64. The default value is 60
(NTSC), or 50 (PAL). The default value is a higher setting, which reduces the
bandwidth consumption and also the image quality. Decrease this value if you
require higher quality images, and bandwidth consumption is not an important
consideration.
Click the Save button directly below the GOV Settings options.
Navigate to Streaming
Under MJPEG Compression setting, in the MJPEG Q factor field, type a value from 1 to
70 (default = 35).
Configuring Video and Audio Streaming | 45
Video Compression (see
Figure
4-2).
800-11873V2 - A - 07/2013
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