AVS Guide to Media Servers, Part 1
If you're like me, you've collected hundreds—if not thousands—of shiny silver discs in various formats, including Blu-ray, DVD, and CD. Not only that, you might also be downloading and/or streaming audio and video content from the Internet. Having access to so much content is great, but it's also confusing, with multiple source devices connected to multiple inputs on your AV receiver or preamp/processor—not to mention finding what you want in a library of discs, downloaded files stored on various computers, and streaming content.
One solution to this problem is a centralized device, generically called a media server, that stores all digital-media files and provides access to streamed content. Of course, this can be accomplished with a media-center PC, but PCs are notoriously complicated to set up, difficult to use, and fraught with anomalies and crashes. This is fine—even fun—if you're a computer geek, but not for the whole family.
Another, more widely palatable option is a dedicated media server, which is really a computer devoted to one function—storing and playing audio and video content. Dedicated media servers normally provide a more intuitive user interface than media-center PCs and are available in two broad categories—those that deal with video and audio and those that deal with audio only. Examples of AV servers include those from Kaleidescape and Mozaex, while audio-only servers are offered by Autonomic, CasaTunes, Meridian (whose audio-server system was formerly known as Sooloos), and Olive.
Let's Get Physical
At the heart of any media server is its hard-disk storage—the more, the better. Depending on the type and level of compression, high-def Blu-ray video can require up to about 15 GB or so for each hour of content, while standard-def DVD video can consume up to about 3 GB per hour, both including a multichannel audio soundtrack. (More highly compressed downloaded video consumes much less space.) Two-channel 24-bit/96 kHz uncompressed audio takes about 2 GB per hour, while CD-quality audio (two channels of uncompressed 16-bit/44.1 kHz) requires a mere 660 MB per hour. Losslessly compressed audio formats such as FLAC and Windows Media Audio Lossless use about half as much as uncompressed files, and highly compressed MP3 files consume less than 60 MB per hour.
These days, media servers can easily provide 1 or 2 terabytes of hard-disk storage, and sometimes much more. With 1 TB, you can store at least 60 hours of HD video, 330 hours of SD video, 500 hours of uncompressed 24/96 2-channel audio, 1500 hours of CD-quality audio, 15,000 hours of MP3 audio, or any combination thereof.
That much hard-disk storage is often implemented in a RAID (redundant array of independent disks). Several physical hard-disk drives are combined in a single enclosure, and data are distributed among them with some level of redundancy and error correction to protect the data in case one or more of the drives fail.
RAIDs are categorized into several levels that define the type of data redundancy, called "mirroring," and error correction, or "parity." These levels are numbered from 0 to 6, which indicate increasing safety of the data. For example, RAID 0 has no redundancy or error correction, making it very unsafe, while RAID 6 provides the most safety. There's also RAID 10, which is a combination of RAID 1 and 0, but it still has no error correction.
In RAID 2, 3, and 4, the parity is stored on a single, dedicated drive, while in RAID 5 and 6, the parity is distributed among several drives. If a data drive fails, the parity information is used to rebuild the data on that drive after it is replaced. A RAID 5 system can continue to operate if one data drive fails, and a RAID 6 system can tolerate two drive failures, though the speed of performance in both cases is compromised until the failed drives are replaced and the data are restored.
The Kaleidescape 3U Server provides space for 14 hard-disk cartridges using proprietary RAID-K (similar to RAID 4) with a total storage capacity of 36 TB. That's enough for about 900 Blu-rays or 5400 DVDs.
If the internal storage isn't enough, some media servers let you expand their storage by adding external hard-disk drives. Some even let you install or upgrade the internal hard disk as higher capacities become available.
Of course, the server must also have AV outputs so the content can be played on a video display and audio system. Video servers have an HDMI output, and all servers have some combination of coax and/or optical digital-audio outputs as well as analog outputs such as component and composite video and analog audio.
Seen here (top to bottom) are the Mozaex Player 3 and RAID Server, which provides up to 15TB of RAID 6 storage.
In some cases, such as Kaleidescape and some Mozaex systems, the server feeds its content to a separate player via the home's local-area network (LAN). With these systems, the player is connected to the AV system.
Let's Get Loaded
If a media server is to consolidate your collection of AV content on discs, it must be able to copy that content from the discs to its hard disk, a process called loading, importing, or ingesting. It's also commonly called ripping, but this term carries the connotation of stealing, as in ripping off, so media-server makers don't like to use it.
The Kaleidescape system includes (top to bottom) the M300 player, M500 player, and 1U server. Not shown here is the 3U server and Disc Vault carousel.
In some cases, such as Mozaex, the server itself provides a disc drive from which discs are loaded, while in other cases, such as Kaleidescape, discs are loaded from a separate player or disc carousel, and the data are sent to the server over the home's LAN. In fact, the Kaleidescape system lets you load up to four discs simultaneously, even while playing multiple streams of content already loaded on the server. Mozaex lets you load one disc while playing one stream.
Meridian Control 15 audio server
The Meridian Control 15 is the only component in the company's Digital Media System with a CD drive and hard disk, which lets you import CDs directly. Otherwise, CDs can be imported to a computer and transferred to the hard disk in a Media Core or Media Drive unit.
Olive 6HD audio server
The Olive 5HD and 6HD both provide CD drives, and they can also import audio files over the home's LAN. The Autonomic, CasaTunes, and Olive 4HD systems do not offer a CD drive, but they can import audio files from computers on the network.
Let's Get Legal
You might well wonder about the legal issues around importing copyrighted content on commercial discs. It is perfectly legal to make copies of CDs that you own for your personal use, so you can load your entire collection to a server with no legal worries whatsoever.
However, DVDs and Blu-rays are a different story. Unlike CDs, the data on both types of video discs are encrypted to prevent copying, and makers of all legitimate disc players must license the encryption scheme in order to play the discs. For DVDs, the Content Scramble System (CSS) is licensed by the DVD Copy Control Association (CCA), while Blu-rays use the Advanced Access Content System (AACS), which is licensed by the AACS Licensing Administrator (AACS LA).
In order to load DVDs and Blu-rays onto a media server, these encryption schemes must be defeated—and both have been, even though this is generally illegal under the Digital Millennium Copyright Act (DMCA). There are a few exceptions, but "space-shifting" (making copies for use in the owner's digital devices) is not one of them.
In 2010, a US District Court ordered RealNetworks to stop selling its RealDVD decryption software, though there are lots of similar programs available. And after a protracted court battle between the DVD CCA and Kaleidescape, the server company and its agents (dealers, etc.) have been enjoined from making or selling any product that copies and plays DVD content from a server. As of this writing, that injunction has been stayed pending an appeal by Kaleidescape. Meanwhile, the company continues to make and sell media servers that can import DVDs and play the copies directly from the server.
Blu-ray is a different kettle of fish. The AACS license states that you can make as many copies of a Blu-ray disc as you want, but you can play only one copy at a time. (Kaleidescape contends that the DVD CSS license includes no such provision, which is one element of the ongoing legal case.) The play-only-one-copy-at-a-time rule means that, if you want to play the copy on the server, the physical disc must be precluded from playing under any circumstances.
How does Kaleidescape get around this? By requiring the Blu-ray disc to be in one of its players when you watch something copied on the hard disk. If the disc is in a Kaleidescape player, the system makes sure it can't be played at the same time as the server copy. Of course, this is pretty inconvenient, negating some of the benefit of a server. After all, the whole point is to consolidate all your content without having to deal with physical discs.
Kaleidescape M700 Disc Vault
Kaleidescape addresses this issue by offering multi-disc carousels called Disc Vaults that can hold up to 320 DVDs and/or Blu-rays. Content can be loaded onto the server from a Disc Vault, and titles on the server can be played as long as the discs from which they came are in the carousel. A system can have multiple Disc Vaults, so you can store a collection of any size, though this can get very expensive.
Mozaex solves the encryption problem differently. While its servers and players include licensed decryption software for playing physical discs, they do not provide unlicensed decryption software for copying DVDs and Blu-rays to the server. Instead, the company shifts this responsibility entirely to the user. According to Mozaex, the DMCA makes it illegal to make, sell, or give away unlicensed decryption software, but not to acquire or make legal use of such software.
But what constitutes legal use of decryption software? Mozaex cites expert opinions that copying DVDs and Blu-rays for personal use "may well be" lawful under the Fair Use Doctrine, but I've seen other expert opinions that maintain it is still illegal. And the Mozaex website advises its dealers not to use decryption software to load encrypted content onto the server for their customers, even content owned by those customers. It also suggests that dealers might want to have buyers sign a "hold harmless" agreement to cover their legal bases.
What about importing SACDs and DVD-Audio discs? Both formats are encrypted, so the legal issues apply. But I know of no media server that provides the ability to copy either type of high-resolution audio disc to its hard disk, so this concern is moot.
Let's Go Home
Of course, none of this legal rigmarole applies to home-made videos, photos, and other self-generated content, which can be loaded onto the server or, in some cases, streamed from other computers or storage devices on the home LAN. In particular, many networked media systems can include a device called network-attached storage (NAS), which is a high-capacity hard drive connected to the LAN.
If you want to stream content from other devices on the LAN to the server or player, they all need to recognize and communicate with each other. One way that server companies support this is by implementing a set of networking protocols called UPnP (Universal Plug 'n' Play).
In order to play videos, photos, and music from one device to another over the network using UPnP, they must also be compatible with a standard called DLNA (Digital Living Network Alliance). This standard defines different types of devices and files that can be streamed between them, supported encryptions and resolutions, control parameters, and copy-protection issues. All DLNA-compliant devices use UPnP to communicate with each other, but not all UPnP-compatible devices are DLNA-compliant.
The Mozaex system can stream from a NAS, but it employs a proprietary protocol, not UPnP/DNLA. Kaleidescape and Meridian offer no such capability other than their own, proprietary hard-disk units. The Autonomic and Olive systems can stream audio files on a NAS or networked PC using UPnP/DLNA, while CasaTunes is planning to add this capability this year.
Let's Go Online
Aside from imported discs and user-generated videos and photos, another important source of audio/video content is online streaming and downloading, which many media servers can accommodate. Streaming from providers such as Netflix, YouTube, Spotify, and Pandora is more common, because the content is played as it arrives from the Internet—no copy is stored on any device in your home, so there are no copy-protection issues to deal with.
Autonomic MMS2 audio server
However, you must have sufficient online bandwidth to receive the stream without interruptions. If the available bandwidth is not enough—for example, if others in your home are also streaming or downloading large files—the program you're trying to watch or listen to might pause occasionally while some of the data accumulate in a temporary buffer.
How much downstream bandwidth is enough? For Netflix video streaming, you need at least 3 megabits per second (Mbps) for what the company calls "DVD quality" and 5 Mbps for high-def quality. Vudu specifies 1 Mbps for standard def, 2.25 Mbps for 720p HD, and 4.5 Mbps for 1080p HDX. By contrast, streaming compressed audio requires much less bandwidth—Pandora Internet radio recommends at least 150 kilobits per second (Kbps) or 300 Kbps for its "High Quality" audio, while Spotify recommends at least 256 Kbps, and MOG streams at 320 Kbps.
Then there's downloading, in which AV files are sent from the content provider over the Internet and saved on the server. This is the paradigm used by iTunes. In this case, your downstream bandwidth is less critical—the file takes as long as necessary to download, pausing whenever it needs to. When the file is safely stored on your server, it can be played without interruption because, presumably, the bandwidth of your home LAN is higher than the downstream bandwidth coming into your home—typically, 10 to 100 Mbps up to 1 Gbps.
Some download providers sell content outright, while others let you rent titles for a limited period of time. Buying a downloaded title is just like buying it on Blu-ray or DVD—you can play it as many times as you want for as long as you want. In addition, you might be able to download or copy it to several devices, subject to its digital rights management (DRM).
By contrast, renting a title from a provider such as Vudu lets you play it only for a limited amount of time. For example, you might have 30 days to start playing a rented title, after which you have 24 or 48 hours to finish watching it. After that, the file becomes unplayable.
A relatively new development in the world of online content is cloud storage—for example, using a service called UltraViolet (UV). This service lets you store your copy-protected content "in the cloud" (on a remote server maintained by someone other than you), including content on UV-compatible physical discs, and stream it to any of your playback devices. You can also download owned content from your cloud-based "locker" a limited number of times.
CasaTunes Xli audio server
The Mozaex server can stream from Netflix, Vudu, and Hulu Plus as well as download from iTunes. Kaleidescape is currently working on its own "electronic delivery store," which will be an online retailer of movies. As for audio servers, the Autonomic, CasaTunes, Meridian, and Olive systems can all access various audio-streaming and Internet radio services.
Another new feature of some server systems is the ability to play content from iOS and Android smartphones and tablets. The CasaTunes and Olive systems can access audio content on both platforms.
Android and iOS mobile devices also provide a new way to control these systems, but that will have to wait until the next installment, in which I'll also discuss user interfaces, multi-room distribution, and advanced features.
For more info on the systems I've mentioned in this article: