VBrick 6000 series Admin Manual page 38

Resolution
Rate Control
Method
Target Bit Rate
28
The pixel Width and Height of viewed video on the PC screen (Width
by Height). Regardless of whether the transmission is NTSC or PAL,
the following resolutions are possible:
• 320 x 240
• 256 x 192
• 192 x 144
• 128 x 96
• 64 x 48
If NTSC or PAL-M is selected, the following resolutions are available:
• 352 x 240 (SIF)
• 176 x 128 (QSIF)
If PAL is selected, the following resolutions are available:
• 384 x 288
• 352 x 188 (CIF)
• 176 x 144 (QCIF)
The selections are shown below. The interrelations between these
terms are complex. Use of VBR should be restricted to controlled
environments where significant burstiness in the achieved bit rate is
acceptable. Not all players and/or networks may handle high levels of
burstiness. Default is CBR-CFR. The abbreviations refer to:
• CBR – Constant Bit Rate.
• VBR – Variable Bit Rate.
• CFR – Constant Frame Rate.
• VFR – Variable Frame Rate.
Bits/second. This number represents how much data the VBrick will
send out each second to carry video to an MPEG-4 player. The word
target is used because the VBrick can vary its bit rate slightly in
response to the amount of detail in the movie or camera output. The
discussion of Rate Control Method has more detail. Note that bit rate
determines how much data the VBrick sends in one second to contain
one second of the video or camera output. The more data the VBrick
sends in one second, the more clearly the details of the movie will be
seen on an MPEG-4 player. It is not always possible to send the most
possible data, since that requires a large network "pipe" (connection).
The trade off is the level of detail in the video with the use of smaller
network connections. The difference between "constant" and
"variable" bit rate is that if "constant" is chosen, then the VBrick will
make a strong effort to ensure that the chosen bit rate is reached as
often as possible. The "variable bit rate" setting allows the VBrick to
change how much data it uses in a second (within limits of course), so
that less complex scenes can be sent using fewer bits.
© 2009 VBrick Systems, Inc.