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 May 1, 2005 Drowning in CDs? Create a Digital Archive: Part Two In Part One, I looked at how hundreds of audio CDs can be squeezed into a manageable digital collection for both preservation and gigajukebox listening convenience. The processes outlined raised a few more questions of their own. In Part Two I look at some additional issues of creating a digital music archive, and some enhancements that can make your listening experience more enjoyable.Track gaps: the space between The keen reader of Part One will have noted that following my instructions to create a lossless digital archive fell short of making exact replicas of the original audio CDs. The problem is the gaps between tracks. We may have faithfully archived each track, but what about, as Dave Matthews would croon, "the space between"? Most audio CDs have a standard default gap of two seconds between tracks, but many do not. And continuous discs -- dance mixes, concept albums, classical music -- run together two or more tracks seamlessly. On the other hand, some discs have unusually long gaps between tracks, such as before so-called "hidden" tracks -- usually because the studio engineer thought it would be a fun thing to do. If I wanted to re-create an original audio CD using my lossless archive files, I would have to manually specify track gaps or accept the usual two-second default. If I knew that a disc was meant to be continuous, I could re-create it that way by configuring the CD-burning application to burn without gaps. But that knowledge isn’t stored anywhere in the data, only in my head. In addition, gapless playback of compressed music is a problem for some software, particularly when using the MP3 format. If you feed ten album tracks that are supposed to run together into an MP3 player, you’ll usually get pauses between them. This is true of popular playback software such as WinAmp and iTunes, as well as of most portable hardware players, such as the Apple iPod. There are exceptions -- the excellent but somewhat geek-oriented program Foobar 2000 for Windows supports gapless MP3 playback. And there are plug-ins for WinAmp that can effectively produce gapless MP3 playback through read-ahead buffering. There is a preferred solution to these issues. Ideally, we would have ripped the original audio CD as one large file. This would truly be an exact of the original, including gaps. The rip would need to be accompanied by a cue sheet, a companion file detailing precisely where each track index is within the file -- otherwise, there would be no way to navigate the copy of the disc. The cue sheet also contains the metadata for each track, such as artist and title. With a cue sheet, you get the best of both worlds: an exact replica of the original disc that can played as a single unit, or the ability to pick individual tracks. Cue sheets are a wonderful idea. The problem is that they are not yet widely supported. Both Exact Audio Copy and Easy CD-DA Extractor for Windows do support ripping a CD into a single file and creating a proper cue sheet. Because this is an emerging technology, you should check the latest updates for your preferred software, which may add cue-sheet support in the near future. Also in Windows, both Foobar 2000 and WinAmp (with an appropriate plug-in such as CUE Player or mp3cue) can support playback of cue sheets. Album art As time marches on, everything seems to get smaller. Unfortunately, our eyes don’t seem to be getting any better. LP covers shrank to CD inserts, which have now shrunk further into 200-pixel Web thumbnails. Despite that, some playback applications allow you to display album art while a track is being played. It’s kind of cool. Because none of the ripping software I used in Part One offered the ability to retrieve album art, I pursued this step retroactively. In Windows you can use software such as the free Album Cover Art Downloader or Tag and Rename. Both programs connect to www.Amazon.com -- the covers you see there are what you’ll get. Mac OS X users can try the Clutter program or drag album-art images directly from Amazon.com into iTunes. An album’s cover art can be stored as a small JPEG image file in two ways: as a file in the album’s folder, or embedded in each track’s tag. Some players support one style, some the other, some both. When you store cover art in an album’s folder, it will be saved with a standardized filename: "folder.jpg." Playback software such as Windows Media Player 9+ and WinAmp with plug-in (Toast, Cover TAG) read this file and display it while the music plays. You can also store the album-art image in an individual track’s metadata tag. This can be inefficient for an entire album because you’re storing multiple copies of the same image. On the other hand, if you move individual tracks to other locations, they’ll retain their cover image. Some of the same software players that support "folder.jpg" album art will also find and display tag-embedded covers. The popular iTunes player will display only cover art embedded in the file. Some newer, portable hardware MP3 players, such as the Creative Zen Portable Media Center and Archos Gmini 400, have screens that can display cover art embedded in music files. Volume knobbery If you’ve ever made a mix for a romantic interest, a Mother’s Day gift, or yourself, you know the problem that plagues them all: volume fluctuation. You quickly grow tired of lunging for the volume control every time a new song comes on. Listening to your digital music archive can be like a huge mix tape. There are various approaches to normalizing tracks so that they share peak or average volumes and don’t fluctuate wildly from one album to another. Some normalization and volume-leveling routines manipulate the audio data by increasing or decreasing their amplitude. I prefer not to do anything that changes the actual audio data themselves, so let’s forget about these techniques. There are three other, more reasonable solutions, each with its pros and cons: iTunes’ Soundcheck, Replaygain, and mp3gain. Soundcheck and Replaygain support track-gain calculations. Simply put, they can calculate how much volume needs to be added to or subtracted from a track so that all tracks share the same peak loudness. Both store these calculations in a metadata tag -- they do not alter the audio data themselves. A player that supports Soundcheck, such as iTunes and the iPod, reads the metadata and adjusts its output volume accordingly. Players that support Replaygain, such as Foobar 2000 and WinAmp with appropriate plug-in (such as Otachan’s in_mpg123), behave the same way. Replaygain offers Album Gain, another way to calculate volume leveling. Rather than level all tracks in your collection to the same peak, it levels tracks relative to other tracks within the same album. The result preserves the original album’s overall dynamic range. The biggest limitation of Replaygain is lack of support. It is best supported by Foobar 2000, which can calculate and honor Replaygain settings. And with the foo_pod plug-in, Foobar can convert between Apple’s Soundcheck and Replaygain. A compromise solution is offered by mp3gain, a software utility for Windows. Unlike the more idealistic approach of Soundcheck and Replaygain, mp3gain does alter the compressed audio data, though in a lossless way. An MP3 file is divided into frames (not unlike a reel of film), each frame containing data about its volume level. The mp3gain utility adjusts the volume-level data for each frame, to achieve peak loudness across tracks. The advantage is that all players will support the result, because the MP3 data themselves have been altered to adjust the volume. The disadvantage is that some question how reliably the data can be returned to their precise original state, should the need arise. Music everywhere Keeping a large digital music archive on your computer is great for all kinds of reasons -- but what if you don’t want to listen to music at your computer? Maybe your desktop speakers are a source of secret shame, or your 400W PC’s fan sounds like a small Cessna. The easiest way to turn your computer into a music hub is wirelessly -- particularly if you already have a wireless network set up for more traditional purposes (sharing broadband/laptop use, etc.). A slew of wireless streaming media boxes have hit the market -- Apple’s Airport Express, the Roku SoundBridge, the DLink DSM-320 Wireless Media Player, the Netgear MP115 Wireless Digital Media Player, and so on. All of these operate in basically the same way -- using a WiFi network, your computer sends the digital audio data to the box, which has its own internal digital-to-analog converter. Analog audio is fed out to standard inputs on a preamplifier-processor or integrated amplifier. At between $150 and $500, the major differences among these media boxes are in amenities. Some, like the Roku, are stylish, have their own screens to display song information, and can even be operated by remote control. But most are just square boxes that feed music to your amp. At these prices, though, don’t expect an audiophile-grade DAC. It’s all about the music Technical voodoo aside, in creating a digital music archive I have accomplished exactly what I set out to do -- listen to my music. There was a lot of gold hidden away in those plastic jewel cases. Putting it all at my fingertips means that nothing in my collection is now any more obscure than anything else. The reality is that most of us can’t sit in front of our reference systems all day. Work life often means sitting at a computer, and now those hours are complemented by a collection I had amassed but lost access to. I’ve rediscovered numerous old favorites and heard discs I’d never even gotten around to. And, with a complete lossless archive safely tucked away, there’s nothing to worry about should a treasured disc fall victim to an unfortunate fate. …Aaron Weiss
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