Tieline Bridge-IT XTRA, Руководство пользователя

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© Tieline Pty. Ltd. 2015
Bridge-IT XTRA Manual
19.3
Configuring the Jitter Buffer
Jitter, (also known as latency or delay), is the amount of time it takes for a packet of data to get
from one point to another. A jitter buffer is a temporary storage buffer used to capture incoming data
packets. It is used in packet-based networks to ensure the continuity of audio streams by
smoothing out packet arrival times during periods of network congestion. Data packets travel
independently and arrival times can vary greatly depending on network congestion and the type of
network used, i.e. LAN versus wireless networks. The concept of jitter buffering is displayed visually
in the following image.
Jitter buffer management is encompassed within Tieline's SmartStream IP technology which can:
·
Remove duplicate packets.
·
Re-order packets if they arrive out-of-order.
·
Repair the stream in the event of packet loss (error concealment).
·
Manage delay dynamically based on current network congestion.
·
Manage forward error correction (FEC).
Tieline codecs can be used to program either a fixed or automatic jitter buffer and the setting you
use depends on the IP network you are connecting over. Over LANs, WANs and wireless networks
the automatic jitter buffer generally works well. It adapts automatically to the prevailing IP network
conditions to provide continuity of audio streaming and minimizes delay.
A fixed jitter buffer is preferable over satellite connections to ensure continuity of signals.
CAUTION: If a Tieline codec connects to a device that is using non-compliant RTP streams
then the last fixed setting entered into the codec will be enabled (default is 500ms). Non-
compliant devices include some other brands of codec, web streams and other devices.
Tieline ‘Auto Jitter Buffer’ Settings
Least Delay: This setting attempts to reduce the jitter buffer to the lowest possible point, while still
trying to capture the majority of data packets and keep audio quality at a reasonable level. This
setting is the most aggressive in its adaptation to prevailing conditions, so jitter buffer may vary
more quickly than with the other settings. It is not recommended in situations where jitter variation is
significant and/or peaky. (E.g. 3G/multi-user wireless networks). It is best for stable and reliable
links such as dedicated or lightly-loaded WAN/LANs.
Highest Quality: This setting is the most conservative in terms of adapting down to reduce delay.
The jitter-buffer setting will actually stay high for a longer period after a jitter spike is detected – just
in case there are more spikes to follow. This setting is best used where audio quality is most highly
desired and delay is not so critical. Unless delay is irrelevant, this setting is also not recommended
over peaky jitter networks (such as 3G) and is best used on more stable networks where large jitter
peaks are not as common.