How Does Zixi Work?

Challenges for IP video on the Internet

Challenges for IP video on the Internet

The Problem

Despite content producers’ desire to to use unmanaged IP networks for video delivery, they have been slow to completely convert to this networking technology. They’ve been skeptical it could work well enough for them and save them money.

Before Zixi, they had good reason to be cautious. There are three fundamental issues that had to be overcome before content producers would default to IP video as their mainstream transport platform.

Latency, jitter and packet loss are the big, interrelated challenges to pristine Internet video:

  • Latency is delay in the arrival of packets at the destination
  • Jitter, which is related to latency, is the variability and unpredictability in packet arrival time at their destination
  • Packet loss is a designed-in aspect of any IP-based network. IP networks can by design– and frequently do — simply drop packets without notifying the sender.

Live and shorter-length video collaboration, like news reporting from the field or video conferencing, has no tolerance for latency. Jitter, which forces the receiving decoder to spend more cycles collecting and re-ordering packets, simply amplifies the negative effects of latency on video content. Continuous streams of information — video being a prime example — simply cannot tolerate packet loss while maintaining quality. Even packet loss as minor as <0.001% can create a few seconds of disruption in a high-quality video stream.

Distance also plays a role in challenging high-quality IP video. Even at the speed of light, a millisecond of delay is introduced for every 186 miles a packet travels. Latency therefore increases by almost 70 milliseconds for video to travel half way around the globe. To compensate for these issues, video quality gets sacrificed in most solutions to reduce the effects of latency, jitter and packet loss.

The Solution

Zixi delivers pristine IP video on the Internet

Zixi delivers pristine IP video on the Internet — click to enlarge

Zixi works by providing a quality of service (QoS) layer on top of the Internet or other unmanaged IP networks, using the capabilities below. This video-specific transport layer guarantees delivery of video no matter how large the distance between two endpoints or how little latency is required, given sufficient bandwidth.

  • Zixi is UDP-based. User Datagram Protcol (UDP) is a connection-less Internet protocol that avoids the overhead required by stateful connections.
  • Precise clock synchronization. Zixi provides end-to-end time synchronization, enabling Zixi to precisely manage endpoints to deliver the required level of quality.
  • Jitter removal and packet re-ordering. Because Zixi understands video content, it is able to intelligently sequence packets to ensure they arrive smoothly and in order.
  • Real-time rate adaptation and encoder flow-control. Zixi manages encoders to ensure they are delivering data at precisely the rate required to maintain stream quality. Zixi is also aware of and manages the underlying condition of the Internet connection. Internet connections — especially global connections — can vary from second to second. By monitoring endpoints as well as the availability of the IP network, stream quality is ensured.
  • Zixi runs on standard hardware. Zixi can run in PCs under Windows and/or Linux. In a standard configuration, Zixi Feeder is connected to the output of an encoder; Zixi Receiver is connected to the input of an integrated receiver-decoder (IRD). Zixi Broadcaster, running as a cloud service or on-premises, acts as a hub for managing streams, distributing streams to devices and endpoints. Zixi is also integrated into many popular encoders, such as Thomson Networks, Teradek and Haivision. In these cases, Zixi is tightly integrated with the encoder functionality and can even pace the encoder output when Zixi detects network saturation.