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In video tech, there is a term that gets thrown around often amongst the throws of industry jargon that I, as a video-tech newbie, didn’t understand at all. (Well, there are many terms, I must admit. But we live and learn!

And that term, is ‘multicast’. It may seem fairly self-explanatory; casting multiples of something. But how does this relate to video tech?

What is Multicast?

Multicast solves the problem of one device trying to initiate sessions to multiple end points or receivers. You could do the same thing with unicasting (‘uni’ meaning one), so the receivers would create sessions directly to the server and get streaming information that way. But that then means that the bandwidth is getting clogged up with all this information being fed to multiple devices through one single point. You would end up with severe lag, long loading times and plenty of buffering; not ideal.

What multicasting does, is send a direct line of streaming information into the network, and the devices choose to subscribe to that stream if they would like to. Multicast packets have to be routed like any other, but a list of complicated protocols means that devices can subscribe to a multicast stream via a specific IP address.

Multicasting essentially creates faster and more efficient ways for devices to specifically find the shortest route to the server to transfer data faster and with less compression and quality loss.

 What does ABR mean?

In short, ABR stands for Adaptive Bitrate – which at first glance, meant nothing to me. However, with a quick google search and some light reading, I’ve managed to simplify it.

Firstly, people think adaptive streaming and ‘progressive streaming’ are the same thing. They’re not. Progressive streaming is one single video file being streamed over the internet. The video can be stretched and compressed to fit difference screen sizes but regardless of the screen it’s played on, it will always be the same.

The problem with this, is that with progressive streaming, you will see the effects of the video being resized in the quality. A 720p video on a 16:9 widescreen TV is going to look pretty shoddy… And on top of that, you have issues with buffering. The bane of everybody’s life.

Adaptive Bitrate or streaming solves these problems. It allows the host (video provider) to create multiple video files to fit any screen, and the user can then stream their specific video size to adapt. This means that the issue of video quality is no longer an issue.

Buffering is also solved with ABR. Explained simply, most videos play at 24 frames per second, so your internet speed needs to be able to catch up. If your connection isn’t up to par, you’ll get buffering. ABR literally adapts to the speed of the user’s internet connection.

A small video can be downloaded faster than a large video, so if a user has a slower internet connection, an adaptive video stream will switch to smaller file sizes to keep the video playing without buffering.

The difference between adaptive streaming and adaptive bitrate is… absolutely nothing. Bitrate is simply the term that describe the speed of an internet connection. It’s quite literally the rate at which bits of data fly through the air.

Mix them together, and you get…

Multicast ABR! (Surprise surprise…) So, in essence, multicast provides more efficient service with targeted streams to devices. And what ABR does, is adapts the bitrate of the user’s internet to be able to download and stream content faster and in better definition, that is the highest quality that their screen can allow. What more could you want?

Most recently, streaming software giants Wyplay and Broadpeak have collaborated on a project together in which they created their own multicast ABR using the RDK platform (learn more about RDK here.)

The concept of multicast isn’t new to either of these companies – in fact, Broadpeak first deployed their first multicast technology in 2014. However, the need for this technology to improve live streaming session is huge. All throughout the industry, the quality of live streaming through multicast has always been a little slower to keep up, and with people streaming content in 4K, they now expect their live streams to be just as HD as their other content.

This is where the new Multicast ABR using the RDK system comes in, and Broadpeak and Wyplay come together to save the day. Wyplay integrated Broadpeak’s nanoCDN on an RDK set top box to enable multicast ABR live streaming. Take a look at the video below to see how this works:


The RDK Unplugged Team

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