dacs.doc electric

Listening to music of your choice anywhere in the house--this is what whole house audio is all about. This concept goes beyond simply placing radios in each room--rather, there's a notion of having a central repository of music sources that can be accessed from multiple rooms under varying degrees of local control. The conventional methods for implementing this range from the simple (moderately expensive-single stereo with multiple speaker lines running to each room with local attenuators controlling volume) to elaborate (very expensive-multiple amplifiers, speaker lines to each room and a distribution system for infrared remote control signals). Common to all approaches is the need to run multiple wires to each location. A drawback to this approach is that the typical music source (CD carousel) can play only one thing at a time.

Many people today are networking their homes, with some form of network communications in multiple rooms (physical wiring with Cat5/ethernet, wireless with 802.11b, phone line networking or even power line networking). The key factor here is that data can easily be distributed around the house. Why not use this capability for music?

MP3

A recent dacs.doc article discussed connecting a PC to a stereo and provided some basic information about MP3 audio; so I'll be rather brief here. MP3 refers to a method of compressing digital audio that uses lossy perceptual encoding, meaning that the algorithms used for the compression throw away information that human hearing is unlikely to detect (in theory). Decompression will not yield a result identical to the original, but for commonly used amounts of compression, the differences are difficult to hear. Of course, the higher the degree of compression, the less the compressed music resembles the original. With today's encoders, the most commonly used parameters yield MP3 files that play at 128Kbits/second (meaning roughly 1Mbyte per minute of music). Considering that a full audio CD holds about 74 minutes of music (uncompressed- 650Mbytes of information) and the same CD will hold about 650 minutes of MP3 music, the compression ratio is significant.

Being nearly ubiquitous, MP3 is a very convenient form to store music: compact, platform-independent and portable (players are available ranging from MP3 watches to portables with hard disks and even car systems). There is a multitude of software available to encode and play MP3 files for nearly any PC platform at a very reasonable price (often free). I currently have a modest MP3 collection--about 3.5GB (800 songs or approximately 60 hours of music), the majority of which were ripped (encoded) from my CD collection. These music files are located on a server accessible to my entire network. Whenever I get in the mood, I slip some more CDs into my PC drive and rip the contents. Since I've chosen the songs to rip, there's nothing in the repository that I dislike.

Before continuing, there are two soapbox items I'd like to mention: 1) MP3 does NOT refer to MPEG-3, rather MPEG-1 layer 3 audio. There is no such thing as MPEG-3 (a standards activity for high definition video that was dropped when it was realized that MPEG-2 already provided the same capabilities) and 2) think through the practice of downloading all of your music for free from the internet. Regardless of what you might think of the business practices of the recording industry. The fact remains that the musicians rely on sales of their music for a livelihood—no music sales means no income, which will ultimately mean no more music.

Network Solution to Audio Distribution

If we reexamine the audio distribution problem mentioned above, it becomes clear that the necessary pieces are in place for an alternate method for distributing audio. Communication from the content source (server) via the computer network is available in multiple rooms (for my house, every room of interest). This communication channel is available for any form of control, as well as carrying the music. The only pieces of the puzzle left revolve around how to do the communications and what types of devices to utilize.

There are two main methods of moving any kind of content (in this case music) across the network: Push and Pull. For the Push method, a server streams the MP3 data onto the network in either unicast or multicast. Once the music starts streaming, it is pushed continually until the server is told to stop. Typically, a playlist is established for the push stream, controlling the order of play for the songs. A client device listening to the correct port can receive and decode the music. Multiple push streams can be used, allowing the equivalent of multiple network radio stations to be implemented. One example of software for pushing from the server is Shoutcast (www.shoutcast.com/). The load on the server can be significant, since it needs to do some work in getting the music encapsulated correctly and pushed onto the network at the correct rate. Additionally, some pre-planning must be done to create the playlists that will be used by the streaming server. If your intent is to have continuous playing of music, where you can select what to listen to in a manner equivalent to changing the channel on a radio, then the push method might be appropriate for you.

The pull method uses the server as a repository of music, which the client device draws upon. Essentially, the server represents a network accessible hard disk. This configuration is easily implemented via Windows disk sharing or Samba (for the Linux world). Each client behaves as if the music is on a local disk. The load on the server will be minimal in this circumstance. Selection of music on the client depends upon the software used, but typically can be based on playlists or the contents of subdirectories. The key factor here is that each client has complete, local control over the music being played. I've chosen to use the pull method on my network, due to the simplicity that it offers and the the amount of local control.

Devices

The last piece of the puzzle revolves around the client device: what to attach to the network and how to actually play the music. Playing the music is rather simple--any old stereo will do. Other solutions were outlined in a previous article in dacs.doc. Even if nothing suitable is lying around the house, suitable bits can be found at yard sales for very little cost.

There are a number of off-the-shelf boxes designed to be clients for this very use: the Rio Receiver (www.riohome.com/HomeAudio.htm), the Turtle Beach Audiotron (www.audiotron.net/audiotron/ producthome.asp) and the SliMP3 (www.slimdevices.com/), with prices ranging from about $150 to $300 (there are some other devices with much higher price points, but in my opinion the prices of these other boxes are vastly inflated over the value received). The units listed are meant to be connected to an amplifier (or an existing stereo system) and have form-factors (and visual designs) appropriate for that use.

For those that have the same kind of habits I do--never throwing away a working computer when a new one is brought into the house, there's a cheaper solution. Virtually any obsolete computer (pentium class and above--maybe even a 486) will perform admirably as a network connected MP3 player (again, if one isn't available, yard sales are a good source). At most, a new network card and sound card might be needed (total cost of less than $50). I'm currently using an old Pentium II class machine that my kids will not use, with an old 12" monochrome VGA monitor that was gathering dust in the closet. This all fits into a small end table next to my bed and is connected to the stereo from my college days (I refuse to admit how long that one's been around). The whole point here is that the cost of entry is very low.

The software for playing is available for free. Examples include Winamp (www.winamp.com) and MusicMatch (www.musicmatch.com) for Windows. Equivalent players exist for Apple computers, Linux and even DOS! Examples abound on the internet of people putting together networked MP3 players, including PC parts retrofitted into a case appropriate for inclusion in a stereo rack, ways of getting rid of the keyboard and display (using a keypad and a small serial LCD panel) and so on.

Conclusion

Using a home network for music distribution is certainly practical today, in fact it's probably one of the easiest thing that can be set up on a network. Compared to the alternate methods for doing whole house audio, using a computer network would probably be considered easier to implement, easier to use and much less expensive. The systems that I've put together in my house are being used constantly.