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3
Advanced Configuration
The parameters in the Settings section will have a significant
impact on the quality and bandwidth requirements of the video
stream. In general it is recommended that the default values are
used initially, and then individual parameters can be modified and
tested incrementally to determine if the bandwidth and quality
requirements are met.
For the video streams, the Codec Type options are MPEG4, H.264
or MJPEG. MPEG4 requires the least amount of processing, and
MJPEG requires the most.
Note
The MJPEG type is used for Video 2 and Video 3 for
capturing snapshots and the Live Video feed respectively
It is not possible to select a different type for these streams.
The Bit Rate parameter is only used when the Rate Control
parameter is set to CBR (Constant Bit Rate). With the CBR setting,
the system attempts to keep the resulting bit rate of the video at or
near the target bit rate.
The I-Frame Interval parameter controls the number of P-frames
used between I-frames. I-frames are full frames of video and the P-frames contain the changes that
occurred since the last I-frame. A smaller I-Frame Interval results in higher bandwidth (more full
frames sent) and better video quality. A higher I-Frame Interval number means fewer I-frames are sent
and therefore results in lower bandwidth and possibly lower quality.
An Instantaneous Decoder Refresh (IDR) frame is a special type of I-frame, and the first image in a
stream is always an IDR image. Frames sent after IDR can be decoded without referring to any frames
sent before the IDR. The IDR Factor (1-10, default = 3) indicates how often an IDR frame is sent,
relative to the I-Frame Interval. For example, if IDR Factor is 3, an IDR frame will be sent for every third
I-frame.
The Image Size parameter controls the video
resolution size and therefore can have a
considerable impact on bandwidth usage.
The larger the size of the frame, the better the
resolution and the larger the network
bandwidth required. The following table
provides the corresponding resolution for
each Image Size setting.
As a rule of thumb, if the video will be viewed
on its own and on a reasonably large screen,
a large image size setting may look better. On
the other hand, if the video is shown as a tile
in a video wall, a smaller image size may look
as good and consume less bandwidth.
427-0073-12-12 Version 120
Table 3-2: Image Size Settings
Image Size
D1
4CIF
VGA
CIF
SIF
QVGA
QCIF
May 2015
NTSC
PAL
720x480
720x576
704x480
704x576
640x480
N/A
N/A
320x240
353x240
352x288
320x240
N/A
N/A
176x144
3-20
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