WHITE PAPER | DELIVERING LOW LATENCY VIDEO ACROSS THE INTERNET
Jitter: Occurs when packets are delivered with inconsistent
timing, or even out of order. Jitter can have an exponential
effect on latency and can become a significant problem if
not accounted for.
In order to deliver live video across the public internet, you
have to select the best option for your network topology
and how your audience will consume the video.
• Segmented streaming
• Packet retransmission
• Forward error correction (FEC)
• Haivision’s Secure, Reliable, Transport (SRT)
Let’s explore the advantages and disadvantages of each of
Segmented Streaming: Segmented streaming (also
known as file-based streaming or chunking) is one of the
most commonly used technologies to transport video
over the internet, slicing video content into 3-10 second
file segments. When the video reaches its destination,
the video files play sequentially with no visible break. A
three-second file segment can easily compound into 30
seconds or more of delay before playing at the destination.
Segmented streaming packet loss is protected by TCP/IP
Packet Retransmission: Packet retransmission is the
basis of TCP/IP, a protocol used in almost all internet
transmissions of information. The sender holds onto a copy
of sent packets until the receiver acknowledges receipt. If
no acknowledgement is received within a certain time,
the sender resends the packet. Although this solution is
effective for non-time-sensitive video transmission, it lacks
the speed to be used in low latency applications because of
the extensive back and forth of signalling and buffering.
Forward Error Correction (FEC): Typically used by
broadcasters, FEC reverse calculates redundant information
sent with the base data to rebuild missing packets should
a packet go missing. This increases bandwidth and latency.
FEC is suitable for use in predictable networks that have
minimal packet loss, like a secure campus network or a
satellite connection for example. But FEC is ineffective in
more unpredictable IP networks, as significant packet loss
cannot be overcome.
Overcoming Video Transport Challenges
IP OVERHEAD -20% to 30%
COMPRESSED AUDIO 64 to 256 kbps
COMPRESSED VIDEO 300kbps to 20Mbps
FEC OVERHEAD -15% to 25%
Intermediate Network Devices: Devices including
streaming servers that replicate and repackage video
streams can add latency to video transmission.
Physical distance: Since the speed of light is a limiting
factor in all optical networks, the physical distance between
end points must be factored into planning. Longer distance
means more latency.
IT firewalls: Bridging between networks or streaming
protocols may add latency, so the impact of firewalls needs
to be considered.
Although designing the ideal solution for transporting high
quality, live video over the internet can be challenging, using
today’s protocols and technologies, it is possible.
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