Multicast video transmission vs. Unicast video transmission methods

describe the imageMulticast video transmissionWhen looking for the most effective way to manage video in a security system, there are two often-discussed video transmission methods: Multicast and Unicast. Both have their benefits, but which is best for security applications?

Multicast is a method of one-to-many transmission which is often deployed in IP applications of streaming media. Multiple viewers can simultaneously tap into a single transmission from one source.

Television programming is a perfect analogy. When you want to watch HBO you tap into the HBO feed on the cable network, not to a dedicated signal of HBO. If your cable box is authorized, you get access to the existing stream of HBO on the cable network.

To benefit from Multicast, multiple simultaneous views of the same stream are required. For customers who have multiple operators viewing the same live cameras, Multicast may be a benefit.

However, in most security applications, Network Video Management Systems (NVMS) are used to view recorded video much more than live video, like reviewing video from a specific date and time, around an alarm event, or reviewing video as part of an investigation. Since all recorders, including the most advanced multicast-based recorders, are based on Unicast video streaming for playback, there really is no gain on operation performance by utilizing Multicast network.

To realize significant benefits from Multicast transmissions, a multicast-enabled network must be constructed to enable single stream replication on the IP network, making it available for every user looking to view it.

Multicast stream can only be used on the Local Area Network. Operators communicating over a wireless connection or over the corporate WAN will communicate using Unicast stream by default, and will not gain from the Multicast capability. In addition, IT departments are wary about enabling Multicast on their network due to security reasons, not to mention the cost associated with it.

Is Unicast a better option?

With Unicast transmission, every user in the network who would like to view video will receive a dedicated video stream from the Video Management System (VMS). Compared to Multicast transmission, Unicast does utilize more bandwidth; however, these streams are only required between the source and the “viewer”, and do not affect the entire network (as a Multicast transmission would.)

With VMS implementation of advanced video compression technology and the ability to maintain symmetric bandwidth management of video, users can manage multiple high-quality video streams on a Unicast network without the deployment of Multicast transmission.

To summarize, Multicast transmissions do offer the benefit of lower bandwidth consumption, but comes with higher network construction cost.  Unicast provide cost-savings on the construction of Multicast-enabled networks while maintaining real-time, low latency, high-quality video with adequate bandwidth management for all users on the network.

At American Dynamics, we believe in empowering customers to invest in enhancing their security systems rather than investing in the construction of new IT equipment. VideoEdge is a Unicast-based network video recorder. Unlike Multicast-based digital video recorders that are dependent on the network to manage the video streaming (the Multicast network managing video transmission), VideoEdge utilizes advanced network management techniques that provide higher operational performance.

Note: Most recorders that are dependent on the multicast network to manage the streaming have different performance levels (e.g. 200 or 300Mbps write to disk, while operating on a multicast network compared to 100 or 150Mbps write to disk, while utilizing Unicast network.) The main reason is that these recorders are now tasked with the video management and are not capable of symmetric bandwidth management.

VideoEdge’s advanced networking architecture manages the video in real time. When a user requests video, live or instant playback, VideoEdge responds with no latency. This advanced architecture does not strain the system resources and, as a result, the rack-mount VideoEdge Network Video Recorder maintains full performance of 400Mbps write to disk, 400Mbps video streaming to client, with the Desktop maintainng 50/50Mbps, while providing metadata generation on all cameras. This is accomplished with no video quality degradation or frame-rate loss, all the time on all cameras.


Have any questions about Multicast or Unicast video transmissions; post them in the comments section below.

Technology for Safer Schools

safer schoolsViolence in American schools over the past two decades has resulted in the real need for an increase in security technology in the school setting. Federal government initiatives like Safe Schools, Healthy Students have been created to bring together school officials, law enforcement, and surrounding community leaders.

Along with federal grants, these initiatives have helped generate a national awareness for the increase of school security technologies to help keep our schools safe. Be sure to read Cheryl Shea’s blog post, “Technology for Safer Schools”, on the Tyco Security Products Blog to see what types of technologies are being deployed in the school setting and how manufacturers like Tyco Security Products are working to meet the specific requirements and limited budgets of this industry.

What are your areas of concern regarding school safety, let us know by leaving a comment.