Roku's Networked Music Player Streams Digital Music from PC to Stereo System via Blackfin®

Digital media has become a major force in electronics sales, with consumers searching for greater quality and a more convenient entertainment experience. Still, consumers often find it difficult to take full advantage of digital media. That's because while most digital media (such as music files) reside in a home computer, consumers want to access the media via an application-specific medium (i.e. a stereo system).

Roku, a privately held company based in Palo Alto, California offers a product called SoundBridge™, which lets consumers play digital music files, connecting a stereo or powered speakers to a computer's digital music library. WMA, MP3, AAC, AIFF and WAV music formats are supported. SoundBridge is also network-ready with wired Ethernet or Wi-Fi, allowing users to listen to their digital music collection in any room of the house.

To be successful in the market, SoundBridge had to be affordable enough to appeal to a mass audience, yet powerful enough to execute rich audio features and networking services. Today, SoundBridge is based on what Roku's marketing literature dubs a "super fast" 400 MHz Blackfin® processor from Analog Devices, Inc. (ADI), giving it more than enough headroom to handle powerful features such as simultaneous real-time music visualizers, music decode, user interface (UI) browsing, wired and wireless networking, and future software updates

Managing a Home Music Library
Almost all music is distributed today in digital rather than analog form. Until recently, most digital music was sold on compact discs (CDs). But today, a new method of distributing digital music has become increasingly popular – transmission of files via the Internet, followed by storage on home computers. Music distributed in this manner typically is played back either through stereo systems attached to the home computer or through portable devices. As for all of the CDs purchased over the years, many sensible music lovers use software such as Apple's iTunes® or Microsoft's Windows Media Player 10 to quickly transfer or "rip" songs to their computer for easy access and in a variety of formats, such as MP3, WMA, AAC, AIFF, and WAV formats.

Roku's SoundBridge is an elegant device for streaming digital music from a computer to a stereo system. SoundBridge connects to a stereo system or powered speakers to play PC or Mac digital music files anywhere in the house via Ethernet or a Wi-Fi network. SoundBridge supports: Windows Media Connect and Windows Media Player 10; Apple Rendezvous™ and iTunes; Rhapsody; and any music service using Microsoft's WMA DRM 10 file format such as Napster, Musicmatch, and WalMart.com. Users can browse, select, and control music from across a room using the SoundBridge display and custom remote control, quickly browsing huge music collections by song, album, artist, genre, or composer with the help of Blackfin's fast processor. SoundBridge supports both wired Ethernet networking, as well as 802.11 wireless networking and has both analog and digital audio outputs.

Why Blackfin Processor?
Last year, Roku's design team set out to develop a leading-edge network music player, which was to be displayed at the Consumer Electronics Show 2004 in Las Vegas, Nevada. They had a number of design obstacles to overcome, and a short deadline of less than one year. Roku's designers wanted SoundBridge to play music from both wired and wireless networks, support a variety of music formats, and include "headroom" for future capabilities, all at a low cost.

Roku chose an ADI Blackfin processor for the job with great results. Blackfin processors are designed to meet the computational demands and power constraints of today's embedded audio and communications applications. The Blackfin Processor offers breakthrough signal processing performance and power efficiency, a RISC programming model, and low cost. Roku's founder, Anthony Wood, also the inventor of the digital video recorder and 20-year veteran of the consumer electronics industry, said, "ADI's Blackfin processor provides the processing performance we needed to quickly stream music from a computer to a stereo system. The Blackfin Processor's price point also allowed us to offer the Roku SoundBridge at a price that's affordable for consumers."

With a Blackfin processor, interfacing SoundBridge to a wireless Compact Flash card was a snap – the generic bus of the Blackfin processor easily interfaced with the Compact Flash Wi-Fi adapter slot via the Blackfin processor's generic address and data busses. Since the Blackfin processor is a general-purpose microprocessor with an easy interface to 16 MB of RAM and 2 MB of ROM, Roku could easily run both wired and wireless drivers on the same processor. Roku purchased a number of programs for SoundBridge from other companies, which easily ran on the Blackfin processor, including the TCP/IP network stack from Kadak and various music file decoders.

Great Tools
About ADI's integrated development environment (IDE), Roku's Wood said, "VisualDSP++ has great compilers and debugging tools. It was a tremendous aid in the development of our product." Roku also found ADI's VisualDSP++ Kernel (VDK) and real-time operating system useful. The VDK has standard libraries and frameworks that allow easy inclusion of boilerplate, class libraries, and value-added IP code. For example, the code for SoundBridge operations and network services was easily ported to the Blackfin processor, saving development and debugging time.

When SoundBridge boots, it runs the VDK, which sets up operating system tasks and spawns threads to perform various operations, such as real-time audio transformations (volume, pitch-shaping, equalization), notify (interrupt handler for remote control), display, and network services, all running on the Blackfin processor.

Network services include Apple Rendezvous, which is actually technology known as Zeroconf and/or IPv4LL, and is implemented in Mac OS, Microsoft Windows, in every network printer, and in many assorted network devices from a variety of vendors. SoundBridge also includes support for Universal Plug and Play (UPnP), a set of standards for interoperability of networking devices that extends the UPnP concept to network devices so that they can be installed and set up without manual intervention. SoundBridge communicates with the "source" server, and communication is specific to the server in use. "SoundBridge is a powerful, highly threaded application," said Wood. "The Blackfin Processor has plenty of processing headroom for SoundBridge's MIPs budget." For future generations of the product, the Blackfin processor offers pin- and package-compatible upgrades.

Gone are the days when consumers rummaged through cabinets looking for CDs. Many savvy music lovers have already organized their large music collections on home computers. Now they can enjoy the convenience of a digitally cataloged music library, using the SoundBridge Network Music Player to browse their favorite music by song, album, artist, and genre from the comfort of their sofa. Cost-effective yet powerful, ADI's Blackfin processor is quietly working behind the scenes to make sure their music is delivered quickly and efficiently.

For more information on the Roku Soundbridge product, please visit www.rokulabs.com.

Read more Customer Case Studies like this...