2.28
MD8000 Multimedia Transport System
MD8000 Rev. H
Delay Adjustment Buffer
The delay adjustment buffer has several functions. It provides for packet buffering in order to
reproduce an accurate video/audio clock and to absorb any network induced jitter. The
Loading Base point setting must accommodate these functions. Additionally, for Hitless
switching both the primary and protect path packets will be buffered at the receiving line board
so that they can be synchronized and aligned by sequence number. Packets through the
shorter route must wait in the
Delay Adjustment Buffer
for the arrival of the same sequence
number packet which has traveled through the longer route.
The
Min
Loading Base
point in the table accommodates accurate clock recovery, but does not
include any buffering for network created jitter or timing fluctuation. Typically the setting will
be made for the longer route packets first. This will be the minimum plus some number of
packets to accommodate network jitter and timing fluctuation. The shorter route packets must
stay in the buffer longer than this value in order to be synchronized for Hitless switching. The
MD8000 will automatically synchronize the shorter route packets to the longer route when the
receiving function is enabled. Users are allowed to change the default Loading Base point
within the range between the Min and Max frames. However, in order to absorb the network
fluctuation and jitter, the Loading Base point should have some margin above underflow (12
for the VIF board) and under overflow (64,512 for the VIF board) points.
Figure 2-27: Hitless Buffer Characteristics (VIF Board)
The physical buffer size of an individual board type constrains the maximum arrival time
difference between the two routes that can be accommodated as well as the min and max
Loading Base points. The difference between the Overflow point and user specified Base
Loading point must be greater than the arrival time difference between the primary and protect
paths.
Figure 2-28: Arrival Time Difference to be Accommodated
If it is expected that upon failure and restoration of the shorter route, the shorter route will
become longer than the previously longer route, then the Loading Base point for the initially
longer route should be set to accommodate this situation. This will allow an automatic delay
adjustment without video transport interruption. In other words, additional buffering should be
Summary of Contents for MD8000 Series
Page 1: ...MD8000 Multimedia Transport System Operational Manual For Release 8 21 MD8000 Rev H ...
Page 2: ......
Page 3: ...MD8000 Multimedia Transport System Operational Manual For Release 8 21 MD8000 Rev H ...
Page 6: ......
Page 12: ...vi MD8000 Transport System MD8000 Rev H This Page Intentionally Left Blank ...
Page 20: ...1 8 MD8000 Multimedia Transport System MD8000 Rev H This Page Intentionally Left Blank ...
Page 56: ...2 36 MD8000 Multimedia Transport System MD8000 Rev H Figure 2 32 SWCNT 2 State Transition ...
Page 60: ...3 2 MD8000 Multimedia Transport System MD8000 Rev H This Page Intentionally Left Blank ...
Page 66: ...3 1 6 MD8000 Multimedia Transport System MD8000 Rev H This Page Intentionally Left Blank ...
Page 70: ...3 2 4 MD8000 Multimedia Transport System MD8000 Rev H This Page Intentionally Left Blank ...
Page 78: ...3 3 8 MD8000 Multimedia Transport System MD8000 Rev H This Page Intentionally Left Blank ...
Page 84: ...3 5 4 MD8000 Multimedia Transport System MD8000 Rev H This Page Intentionally Left Blank ...
