Vodavi NomadIP, Руководство пользователя

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Telenium
IP
Tech Specs
82
December, 2005 Vodavi Telenium IP Product Guide
mobility ▪ presence ▪ collaboration ▪ convergence
Video (Nomad
VP
)
H.263 (QCIF : 176 x 144) with 8 Frames Per Second
- Normally sends changed parts (8x8 DCT) and/or motion information (Motion Vector):
Inter-Coding
- Little motion while talking : 200 ~ 300 Bytes Per Frame
- Normal/Heavy motion while talking : Around 1000 Bytes Per Frame
- Full picture frame is sent when (1) Start of Video Coding, (2) Packet Loss : Intra-Coding
- Generally, around 4000 Bytes (Depends on picture complexity)
- Average packet size depends on picture complexity, motion, etc.
But, if we assume average packet size as 600 Byte,
- Bandwidth (bps) = (Packet Header + Payload) x Packets Per Second x Bits Per Byte
= (58 + 600) x 8 x 8 = 42112
= 42.11 kbps (For one frame, 5.26 kbps)
- For Two-Way Communication (Rx & Tx),
Bandwidth (bps) = 42.11 kbps x 2 = 84.22 kbps
* Full picture frame will be sent as multiple packets because it is larger than the maximum
possible RTP payload size.
Packet MTU size information
All the Telenium
IP
devices (except remote devices) use 1500 bytes as their MTU value,
but length of packets from Telenium
IP
devices is less than 1024 bytes. In most
cases, packets are less than 300 bytes. This includes voice packets.
The RSGM (remote device) uses an MTU value of less than 1500 bytes because it may be
directly connected to a PPPoE interface where additional encapsulation of packets
is used. This is only for data communication packets, not for Telenium
IP
signaling/voice packets. In some cases, a PC connected via the RSGM may
use network applications that may fully utilize the MTU. This may cause problems in some PPP
oE environments, because PPPoE encapsulation needs additional bytes for its own header infor
mation.