VBrick Systems VB6000 Series Getting Started Manual page 27

Note Operation with the DSL4000 requires B frames for correct audio/video
synchronization.
Table 2. Reference Distance Settings
GOP Length (N)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
† All I frames.
†† Undefined.
MPEG-2 Delay
This discussion is relevant only for encoder models ending in –xxx1/–xxx2. Low delay mode
is primarily recommended for conferencing applications. Various video artifacts appear when
content with rapid scene changes is encoded at low data rates in low delay mode. The
reference distance is restricted to 1 (no B frames) in low and medium delay modes. If the
Intrapicture distance is set to 1 (all I frames), video disruptions are minimized, but picture
quality is degraded. With other GOP settings, picture quality is improved, but video
disruption may occur on scene changes. At approximately 6 Megabit video rates and above,
video disruption will not occur, depending on content. In low delay mode, delay will be in the
range of 180–190 milliseconds. Video instability is eliminated at medium and high delay
VBrick Appliance Getting Started Guide
Reference Frame Distance
1 2
† ††
IP ††
IPP IBP
IPPP BIBP
IPPPP IBPBP
IPP. . . PP BIBPBP
IPP. . . PP IBP. . .BP
IPP. . . PP BIBP. . .BP
IPP. . . PP IBP. . .BP
IPP. . . PP BIBP. . .BP
IPP. . . PP IBP. . .BP
IPP. . . PP BIBP. . .BP
IPP. . . PP IBP. . .BP
IPP. . . PP BIBP. . .BP
IPP. . . PP IBP. . .BP
IPP. . . PP BIBP. . .BP
IPP. . . PP IBP. . .BP
IPP. . . PP BIBP. . .BP
IPP. . . PP IBP. . .BP
Streaming Video Basics
3
††
††
††
IBBP
††
BBIBBP
IBBPBBP
††
BBI. . .BBP
IBBP. . .BBP
††
BBI. . .BBP
IBBP. . .BBP
††
BBI. . .BBP
IBBP. . .BBP
††
BBI. . .BBP
IBBP. . .BBP
19