Computer Music 6: raw or compressed?

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If we intend to copy music onto our computer for later playback we have to first chop the music into small chunks of the appropriate type. We've already narrowed our choices down to two: raw or compressed. For raw we choose either WAV or AIFF. Compressed, we select one of the two lossless formats, FLAC or ALAC. Let's look at a broad overview of why we would consider one over the other. A lossless compressed file is about half the size of a raw file. A typical CD consumes just under a gigabyte of storage space, 750 megabytes to be exact. If we compress this file using lossless technology, the end result is about half, 375mb. So, compressing your files gives you twice the storage capacity of raw files. Simple enough, right? So it seems a no brainer to choose lossless compression - especially since the file can be unfolded (uncompressed) to its original form. But I would suggest two considerations before making this decision: do you need the extra space and how are you playing it back? My library is a mix of lossless and raw, CD resolution, DSD (single and double), and high resolution PCM. It is varied like this because much of my work is testing stuff and their sound. If the library was built from scratch, I'd only use one format. On my travel computer, a Mac Mini, the vast majority is stored as raw. That's because my library is relatively small - under 1000 albums. But damn! 1000 albums is a LOT of music. It's 48 days of uninterrupted music. I've stored my entire library on the internal hard drive of the Mini. But there are times I want more, and I simply plug in another drive to the USB port. A decent 2 terabyte drive in a USB enclosure (3 months worth of uninterrupted RAW files) costs about $70 on Amazon. That's a lot of storage. If your internal hard drive is 1tB, you've got enough room for about 1000 albums, both high rez and CD quality. So, our first question needs to be answered. How big is the library you need? If it's a lot bigger than what I described, you might want to consider compressing the files - if attaching a number of hard drives to your computer doesn't feel good. In general and for most people, I recommend RAW. I have rarely seen newbies to computer audio actually build libraries much bigger than 1000 albums. Oh sure, their eyes might be bigger than their senses when they first contemplate building a library - figuring they'll combine those of their friends and their own. I know I did. When I first started my project I figured "the sky's the limit!" I'll beg borrow and steal music from every source I can - after all - you can't have too much! Right? Well, actually, wrong. But we'll get into that later. And there's one other thing to consider. When you playback a compressed file, your computer, server, Bridge, or player works harder than when you stream RAW. The music file is decompressed on the fly as the processor is sending the music to your DAC. Those extra operations can often manifest as compromised sound. So, rule of thumb. The less work your computer has to do, the better your sound quality. And since memory is stupid cheap, there's few good reasons to compress your music before storing it. Should you choose to compress, the next question is which format to use? FLAC is by far the more popular, though anyone using iTunes would be best served using ALAC. FLAC (Free Lossless Audio Codec) is used with Windows players mostly because it's free and because it's not ALAC. ALAC (Apple Lossless Audio Codec) is recognized by Apple's iTunes, and FLAC is not. What's cool about ALAC is that most Windows and MAC based music servers all recognize ALAC, but not all recognize FLAC. If you're planning on using iTunes, stick with ALAC (though there are workarounds through add on programs like Pure Music). I never use FLAC - but then I am a MAC kind of guy. Tomorrow we'll discuss the two RAW formats. Today's takeaway: Memory is cheap. Don't stress over using too much. Stick with RAW unless you have a very good reason not to.
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Paul McGowan

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