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RTL Nederland Tests Out Z/IPStream

Adaptive streaming offers a seamless switch between bitrates at the user’s device

Online consumption of content, both audio and video, grows significantly each year. Online offerings for movies, TV and music are becoming more and more common. The industry is moving at a fast pace, challenging for engineers who come mainly from traditional radio and have little time to keep up.

Although online streaming of radio is something radio has offered for a long time, I�ve noticed that we haven�t kept up with the latest technology and functionality often offered by online-based video/music platforms. Yet, people demand that we offer any content on any platform or device, without losing any of the functionality of traditional FM/HD Radio � and, of course, for free.


Looking at technical solutions already available for transporting audio and video content (driven by such video on demand platforms as Netflix, Hulu, YouTube and others), we found that they all rely on �adaptive bit rate� technology, a technique that creates streams of multiple bitrates, segments them in a specified length at the encoder side, and offers all bitrates to the client, which decides which bit rate to play.

Adaptive streaming also offers the possibility of a seamless switch between bitrates at the user�s device, depending on factors such as available bandwidth, local CPU/memory resources, and player capabilities. Although there are a few different implementations like Microsoft Smooth Streaming, Apple HTTP Live Streaming and Adobe HTTP Dynamic Streaming, they all work using the same adaptive principles. Yet, we found that none of these offered an audio-only solution suitable for online radio streaming. After closely examining the specifications of these adaptive streaming techniques, we settled on Apple HLS as the best candidate for audio-only adaptive streaming. The reason for this is that HLS has a broad adoption on the market by mobile and tablet devices. For desktop playback, we teamed with JW Player for a Flash player capable of HLS audio only playback. One problem: there were no encoders out there to make it work!

So, together with the BBC, RTL reached out to Telos and began testing its new Z/IPStream X/2 software encoder then in development. This software would generate a multi-bit rate smooth stream, to be ingested by a so-called �origin server.� This origin server would then repackage the smooth stream on-the-fly to Apple�s HLS for client playback. Although it was at the time a beta product, it proved to be production-ready and ran extremely stable; after several months of testing we started using this in a production environment.


Because the Z/IPStream software uses the same adaptive streaming over HTTP as has already been widely adopted by video, it benefits from the use of existing content delivery networks. These networks can handle huge amounts of traffic, so reaching huge amounts of listeners is not a problem. And individual audio-only streams are relatively small, so bandwidth consumption is reduced even further, making an adaptive streaming implementation very cost effective.

A great benefit of the adaptive technique is that, should the CDN platform or network become congested, playback clients sense the congestion and automatically switch to lower bitrates, thus lowering the incidences of buffering. This happens without any end-user intervention. Furthermore, since some firewalls and network proxys filter RTMP/RTSP/RPT traffic, HLS streaming (which is based on HTTP instead) is more likely get through to end-users.


We configured our software so that one of our radio channels is encoded by the Z/IPStream encoder and pushed, via the open Internet, to two origin servers. These servers then dynamically produce either HLS, Smooth or HDS streams (in our case, HLS). The origin servers could even add dgital rights management protection at your request if necessary. The output is easily cached by CDN servers for huge amount of listeners. We�ve been running this setup ever since without any problems.

RTL is using the upgraded Z/IPStream 9X/2 software variant; while the base Z/IPStream X/2 is a very capable software, the addition of the software-based Omnia.9 encoder and audio processing tools to the Z/IPStream 9X/2 provides an even richer tool kit with which to shape sound.

Setup and configuration is easy. The Z/IPStream Web interface, based on HTML5, works in modern browsers with no plug-ins to install. (By comparison, Telos� older AX/E software relied on the Silverlight plug-in.) Depending on the type of audio processing and number of bitrates you wish to generate, you can run multiple instances on a single system.


Z/IPStream software is designed with redundancy and stability in mind. It is possible, in fact, to have separate encoder instances on totally independent servers take the same audio source, and produce exactly the same output! To achieve this, a timecode needs to be present in the source; both encoders will sync to this timecode and independently produce the same output. Both encoders can then send the output to multiple origin servers which will, in turn, repackage the stream in any adaptive streaming format. With this setup you can suffer from an encoder outage, an origin outage and (multiple) CDN servers may be unresponsive. Even with all these outages your stream will still be online. With the use of cloud-based solutions it�s a matter of spinning up new or more instances if needed to meet your redundancy and scaling needs. (See Fig. 1.)

Fig. 1: Network configuration for RTL�s streaming service (flows right to left)

During our testing period, upgrades to newer versions proved to be as easy as running a setup wizard. All settings are automatically migrated to the new version, making downtime minimal. If you have the multi-encoder setup described above, there could even be zero downtime during upgrades. Adding more instances is as easy as a few clicks.

Z/IPStream X/2 can also take advantage of multiple, redundant inputs like AoIP or any local soundcard.


We are happy with the new Z/IPStream product. It has proved to be stable and offers a great set of features. It uses the latest techniques, and gives us the ability to move into the future with online streaming of radio. And we can benefit from future improvements, as VoD services pave the way for us � giving us the time to focus on radio itself.

van Neerden is Senior System Engineer with RTL Nederland.

[email protected]

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