Streaming systems – order in the chaos!

The Big Players

Gapless, sync play, multiroom… etc….

Streaming audio is a complex business. In the “early days,” playing a piece of music over a network was a big deal. But as the years go by, we want more…. and more… and more. Think gapless playback (no pauses between songs…necessary for mix albums and classical music for example), sync play for multiroom audio. And as time progresses: stereo pairing of speakers. Not to mention integration of numerous streaming services.

These are things that we all find quite normal nowadays. But go back ten years and you will see that the landscape looked very different then. And still there are players that don’t support gapless playback – cough…. Audiolab with DTS PlayFi… cough… But let’s look at some systems.

Way back – UPnP

A while back, there weren’t very many good protocols to enable streaming audio – and video. That didn’t really come until UPnP and DLNA (a sort of extension to UPnP). UPnP stands for “Universal Plug and Play.” In practice, that came down to Universal Plug and Pray…. because in the early days it was 100% uncertain if you were going to encounter the device on the network. Not surprising: the majority of network equipment did not have the UPnP extension at all. Think of the router that really needs to be able to handle it.

But as is often the case: time heals all wounds and UPnP became better and better. Now it works just fine. Partly because the infrastructure in the majority of homes is modern enough for it to work.

Please note that UPnP is not necessarily intended for audio streaming. UPnP makes discovery of network devices easy, so that a PC or other network device can quickly find a new device and know what it can do. Think of a media server on the NAS. This tells other devices in the network, for example, exactly what it is, that it is available, what its IP address is and on which port they can access it. That is handy. And more network devices talk to each other this way. Streamers, TVs, smart home hubs, computers, phones, tablets, vacuum cleaners, solar panels, you name it. And thanks to UPnP we know very quickly what is in the network, what the settings of the devices are and what they can do. Super… but basically not an audio streaming protocol…

But DLNA – Digital Living Network Alliance – has changed all that. DLNA is – simply put – an extension of UPnP and ensures that licensed devices must comply with certain standards. It was founded by CE industry brands to make connected devices work together a little easier. Well desired at the time (2003). Also, we guess that the DRM – digital rights management – was a beneficial addition though (among others, Sony was part of the club, and they have some use for DRM :-)). However, we must say that DLNA has made life easier. Streaming has become more mature because of it.

UPnP / DLNA is without a doubt a crucial standard in the world of media streaming. UPnP in particular forms the basis for many streamers (NAIM, dCS, Cambridge Audio, AVM, Heos, Yamaha, et cetera). And custom software or not: the UPnP protocol is often at the core. However, there is a handful that has really written their own protocol. We will come back to that later.

OpenHome

So there are quite a few systems that work with UPnP. And systems based on UPnP. Think of OpenHome. Players from Linn (the developer of OpenHome), Auralic and, for example, Lumin and Esoteric (which uses the Lumin platform).

OpenHome should bring some optimizations to the UPnP protocol, making audio streaming a little better. Think of it a bit like “UPnP on steroids”. And there’s nothing wrong with that: why reinvent the wheel when you can just tweak it?

The nice thing is that OpenHome, because of its ‘roots’ in UPnP, is compatible with many UPnP controller apps. If you have a favorite then it works. Think of the DS Audio app from Synology. However, there are also apps that work with OpenHome, think BubbleUPnP. Bubble has both a server package (for installation on a NAS, for example) and a controller and player software (also included in the smartphone app). It may be a somewhat “nerdy” app, but works like a charm. We often use BubbleUPnP with streamers that do not support Roon and work with UPnP or OpenHome. The reason is that BubbleUPnP can also stream Tidal and Qobuz to a player. This way we don’t have to enter any accounts in the player and we can also use Tidal and Qobuz with players that can’t play them natively. A handy feature.

The Apple counterpart to BubbleUPnP is Mconnect. Your author doesn’t have an iPhone or iPad, but his colleagues have already told him that Mconnect works fine.

Roon

Alpha Audio readers know that we’ve been playing with Roon for a long time. Roon is especially convenient because linking players is incredibly quick and easy and the library integrates seamlessly with Tidal and Qobuz. Also nice. ROON has its own protocol: RAAT. Roon Advanced Audio Transport. This is not UPnP and for that reason Roon can not see or control UPnP players. The only integration Roon allows outside of RAAT is Apple Airplay, Chromecast and Sonos. It can also show album art via Casting to a Chromecast.

The goal of Roon with RAAT is simple: stable streams over cable and wifi and great, broad support on the player side. Even less powerful hardware should be able to work with Roon. And it does. There are so-called ‘endpoints’ (players) that work on an old ARM chip or older FPGA. Without any problems. It runs like a dream on a Rasberry Pi. What also works differently is that the clock in the player or connected dac is dominant: the clock in the endpoint determines the flow of the stream. Not the server.

VitOS

Now Roon itself has many possibilities to get a server or player working. Think of Roon Rock, Roon Server, Roon bridge, the desktop controller or the app of course. But those who – for whatever reason – want something different, or specifically want to work with a Rasberry Pi, can look at VitOS. This, custom, stripped-down Linux operating system runs on a Rasberry and has Roon Bridge integrated. A ‘one stop shop’ so to say!

Diretta

We spoke to the developer of Diretta at the 2019 High End Muchen. He had a very small booth in one of the halls downstairs. However, I found his story interesting. Namely, Diretta is a completely rewritten streaming protocol which focuses on stable timing and a constant flow of data. The reason Diretta focuses on this is that sending data in bursts – as UPnP does, for example – causes peak loads. For example, on the chips on the network interfaces, but also the CPU. And that in turn causes spikes in noise. Something that – according to Diretta – is difficult to filter out.

We know that noise is the greatest enemy of good music reproduction. We have done enough measurements on swiches and filters to know that there is a connection between noise and reproduction quality. Even small amounts of common mode are audible in a system with enough resolution. We therefore find the Diretta protocol particularly interesting.

It is – besides Roon – one of the few protocols that clearly states that it goes for quality and tries to substantiate that their solution works. There are not very many players with Diretta yet. Looking at the partner list we see Spec, Luxmann, SoulNote and for example Sforzato. We are going to see if we can try a player from Spec.

LMS

LMS – Logitech Media Server – is still a popular system. The software is old, but can still be downloaded and works fine under Windows, MAC and Linux. The apps for NAS can be obtained via a detour, but we see a lot of forums full of issues. Our advice: install it via Docker or on a PC running Linux, Windows or MAC OS.

Now we haven’t worked with LMS for over a decade, so we don’t know how it works or performs in practice. We will certainly give it another try, since there are readers who still work with it and say it simply sounds better. We look forward to hearing about your experiences.

Airplay

We all know Airplay. Apple has launched that nicely into the market. Airplay can be seen as a counterpart to UPnP and Chromecast. It makes streaming media incredibly easy because in the controller (the app from which you want to play) you simply tap the Airplay logo and choose a player.

Airplay, like UPnP and Chromecast, can stream both audio and video. Airplay is based on the Apple Bonjour protocol (zero config) for discovery of players, and UDP and RTSP (real time streaming protocol) for sending media. The streams are AES encrypted. Apple, of course, has thrown its own sauce over the protocol stack. For example, the AirPort Express uses RAOP – Remote Audio Output Protocol – which is a modified version of RTSP.

There is a hefty limitation with Airplay, though. First of all, the resolution is limited to 16 bit / 44.1 kHz. 48 kHz is supported for video content. In short: Airplay cannot handle high-res. In addition, quite a few users hear a difference between an Airplay stream and the original stream directly from server to player. So did we. Airplay claims to use lossless compression, but we have the feeling that something is going wrong. Roon – which fully supports Airplay – also indicates that it is not a lossless stream.

Fortunately, there are alternatives to Airplay. Audirvana, for example, is a good player, especially for Apple (And Windows. Audirvana also supports UPnP). But more on that later. A lot of streamers accept streams via Airplay, which is of course nice for users, since it works incredibly easily. There is also a brand that has optimized Airplay, making it sound better: La Rosita.

Chromecast

Chromecast is basically the Android counterpart to Apple Airplay. Chromecast – like Apple Airplay 2 – can stream audio and video. And also with Chromecast, it goes with a simple press on a logo to then choose a player.

Chromecast uses its own protocol: Google Cast. For discovery, the Chromecast uses mDNS: multicast domain name system. So for streaming itself, Google has its own protocol stack about which there are not very many details. However, it will be based on a form of multicast and rtsp.

The difference between Apple and Android in this case, is that Chromecast responds faster. Apple buffers beforehand for two seconds, which causes delay after an action. Chromecast does not do that. Chromecast supports high-res audio (24 bit / 96 kHz) and 4K TV streams.

There are major audio brands that use Chromecast at its base. Think Primare. Roon can also stream audio via Chromecast. And can use Chromecast as a “display” for nice, big cover art. A nice feature.

Closed ecosystems

We have now covered all the major and interesting streaming (or multimedia) protocols, we think. If one is missing, we’d love to hear about it.

Besides these protocols, there are of course the necessary closed systems from manufacturers themselves. Think of Aurender, BluOS and Sonos, just to name a few (they usually support Airplay and / or Chromecast). Know that these systems also lean fundamentally on existing technology. BluOS works on the basis of multicast technology, to name but one example. That is necessary, otherwise it would probably not work with existing infrastructure in users’ homes and it would be much, much too complex.

There is, of course, much to be said for both open and closed systems. Open gives freedom, closed allows the manufacturer to focus more on stability and quality. But you sacrifice freedom. The choice is up to the users. Where do the priorities lie? What do you yourself consider important?