An audiophile's utopia

While it's possible to pipe music around your home, getting everything to work in sync is difficult with today's networks. The answer may lie in better software, says E&T.

Imagine a typical morning. You wake up to your alarm clock radio; you then get up and, as you approach the bathroom, the sound gets steadily louder until you are in closer proximity to the speaker in the bathroom which takes over.

As you move from room to room, speakers turn off and on so that you are always within earshot of your favourite tune without having to drench the entire house with your listening pleasure. Then, as you lock the front door, the music stops. You get in your car, turn the key and the car stereo takes over.

Today, we are used to our music following us wherever we go thanks to the personal stereo revolution, which kicked off in the early 1980s with Sony's Walkman. But within most homes, audio is very much at odds with the modern connected world. Real-time wireless audio is experiencing escalating demand from emerging consumer markets, a demand that manufacturers have so far struggled to satisfy.

Large collections of digital music are becoming increasingly common, with products like the iPod capable of holding thousands of high-quality audio files. In the past few years, a number of media streaming devices have appeared which brings us a crucial step closer to the audiophile's utopia.

These are media streamers which allow us to share the same audio content (but can also include video) between devices in a number of different rooms. Media streamers are designed to wirelessly access a music database saved on a computer within range and transmit it to any connected device.

Sonos

The best known is the Sonos wireless audio streaming system, which debuted at the 2005 Consumer Electronics Show in Las Vegas. Since then, the California-based company has regularly updated its technology.

"Finding and playing music all over the house needs to be so easy that anyone can pick up the controller and play DJ," says John MacFarlane, CEO at Sonos.

The latest iteration, the Sonos Bundle 250, has a new CR200 touchscreen and charging cradle. The ZP120 ZonePlayer has a 55W class-D amplifier and stylish speakers. You set it up by loading the software onto your computer, then plug the ZonePlayers into the mains - at least one needs to be hardwired to your wireless router via Ethernet. You subsequently have to connect it to speakers.

You can set up as many play zones as you have ZonePlayers and play music from a single source, such as your computer or media server. Or you can have different content piped into different rooms - but all from the same source.

The system works with a proprietary 802.11n type wireless network called SonosNet to prevent interference or drops caused by existing wireless Internet traffic. It can stream from any storage device on your network that supports the common Internet file system (CIFS), such as a NAS (network attached storage device).

Like any media player, you can shuffle, repeat, skip and start playlists you've created in iTunes or Windows Media Player, and it can cope with most audio files.

Logitech Squeezebox

The other well known audio streamer is the Logitech Squeezebox. The latest version, the Duet, supports a wide range of music file formats and also sports an online service.

As the name implies, there are two key components of the system - a remote control and the Squeezebox receiver itself. This is a cut-down version of the original Logitech Squeezebox model, lacking any screen or control buttons. The receiver has the necessary outputs on its rear: two analogue RCA audio connectors along with optical and coaxial digital outputs. An Ethernet port is also included for a wired connection.

Both the receiver and remote are easy to set up. You can connect to the SqueezeNetwork to access Internet radio stations. After installation, the software prompts you for the network location of your music database.

Although it supports a wide variety of codecs, including FLAC and OGG, it doesn't support any form of digital rights management - if you use iTunes this could be a problem. The Squeezebox supports podcast access, as well as a host of Internet radio and subscription-based online radio services.

Like the Sonos, the Duet can be connected in multiple rooms. You need to purchase additional receivers to control music in up to three rooms with one remote. You can choose whether to have each room playing different music, or the same songs.

This type of streaming device is establishing itself as something many of us will be purchasing in the near future. However, there is one drawback: they use your existing wireless network, or a variant of it.

Your Wi-Fi network is primarily designed for communicating data, and not audio, in real-time. Therefore, when you pipe your music to different devices, you are likely to experience what is known as 'zone delay'. This is where the audio is slightly out of sync to the extent that it is audible as either an echo or even a cacophony of voices singing at different points of a track.

The problem is that codecs (which incidentally stands for compression decompression) require a degree of processing. This generally adds to the latency of audio when delivered. But there may be an answer.

Bluetooth real-time

Could the solution be Bluetooth? After all, this wireless standard is designed to deliver audio in real time. However, Bluetooth stipulates a maximum available bandwidth for A2DP (advanced audio-distribution profile) of 768kbit/s. So, for high-quality stereo audio it is necessary to use some form of audio coding to reduce the required data rate. But for live streaming, audio coding delays are again prohibitive constraints

Some years ago, the Bluetooth SIG (special interest group) ratified the A2DP to manage the transfer of stereo audio, and the consumer market has subsequently experienced the arrival of A2DP-enabled products on both the audio source and headset sides.

"To achieve CD-quality dynamic range in bandwidth-limited applications, such as Bluetooth stereo headsets, requires the use of at least 16-bit audio as the raw input; a compression technology that can reproduce virtually all of the original dynamic range subsequently transforms this," says Stephen Wray, vice president licensing at Belfast-based audio codec specialists APTX.

The challenge therefore is to find an algorithm that can deliver this quality level with low corresponding latency. Bluetooth is robust and ensures accurate signal delivery, but this focus on resilience results in fundamental delay issues. It uses a series of fixed-size transmission and reception slots, which therefore have response time limitations.

Some years ago, the Bluetooth SIG selected the SBC (smart-bit-rate-control) compression algorithm, developed by Philips, as a mandatory codec to ensure interoperability for Bluetooth because it is freely available, has low complexity in processing overhead, and has better encoding and decoding latency than alternative compression algorithms. The sound quality, however, is inferior when played through speakers.

Currently, APTX has its codec incorporated in a number of Bluetooth products. Most recently, it has been incorporated in Creative Labs' new wireless 2.1 speaker set - Inspire model S2 Wireless. These wireless speakers support A2DP. The transmission uses the apt-X codec, which ensures minimum delays when transferring data.

At this year's CeBit expo in Hanover, Germany, Fraunhofer researchers, inventors of the MP3 codec, and their industrial partners presented their solution for streaming both audio and video room-to-room - WiMAC(at)home (Wireless Media and Control at Home).

At the heart of the system is a TV set which unites several functions in one device. It serves as a digital media archive that can store music, videos and photos and make them available with live TV programmes. Pay TV contents can also be distributed in a protected environment and in compliance with copyright regulations.

The TV can even be connected to automated home systems, enabling heating appliances, alarm systems and air conditioners to be controlled via the screen. All devices in the WiMAC(at)home network configure themselves automatically. New components are incorporated by Universal Plug and Play technology.

The system is based on the specifications of the Digital Living Network Alliance, a global collaboration between computer and consumer electronics manufactures who have set fixed standards for home networking. It is possible to connect notebooks, surround systems, digital video recorders and TVs of different brands.

"New compression techniques for audio and video data enable the best possible image and sound quality for high-resolution and mobile television," explains Andreas Werner of the IIS, one of Fraunhofer's commercial partners in the project.

Music or films are always played back in the room the user is in. If the user leaves the kitchen to go to the living room, for example, the content is automatically rerouted. The user can be located using a Wi-Fi enabled device such as a smart phone. Alternatively, users can authenticate themselves via radio frequency identification.

Thus technology companies have demonstrated that our audiophile's utopia is feasible.

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