Tokyo and tech through the eyes of a split pea

Compression vs Quality

Recent email exchange I thought I’d share:

We’re just debating the sound quality of the new Network Walkman vs. a regular MP3 Player. (We haven’t actually listened to the Network Walkman yet. [X]’s ordered one and I’m debating whether or not to get one.) [X] wants to store all of Bach’s works on his and I want to download all the thick, complicated late German Romantic stuff – like Elektra. Do you think the quality is good enough or does the compression “flatten” the sound?

I understand you can store approx. 13,000 songs on this thing, but what does that translate into in terms of “complexer” music like Bach, Strauss or Mahler?

And my response:

There are a couple ways to answer your question, mostly dependent on usage and life-style, so I’ll start with the shortest.

First, a brief explanation on two different compression categories just so that we’re on the same page – lossy and lossless. Lossy compression means what it sounds like – you lose data. Lossy audio compression – MP3, ATRAC, AAC – uses perceptual properties of human hearing to throw away data never to be recovered again. Lossless compression, on the other hand, simply finds redundancies in the data and uses smaller “markers” to reduce the overall size.

So, lossy audio compression definitely flattens the sound, and you will hear greater distortion at higher compression rates (or lower bit-rates, such as “64kbps”, “132kbps”, etc.; they’re two sides of the same coin). You are right to be concerned with genre as well, since perceived quality will differ among different genres compressed at the same bit-rate. That said, it is generally agreed that at any given bit-rate — let’s say 128kbps — ATRAC, WMA, and AAC are all better than MP3 (in part because MP3 is the oldest of the lot). So between ATRAC and MP3, *if HD space is an issue*, then I would go with the Network Walkman.

Longer Answer

Note how I tried to emphasis HD space. Personally I have found audio compression to be least friendly with classical works. For a while when MP3s were really the only option, 320kbps was accepted as “CD-quality”. Currently, Sony is touting ATRAC3plus at 256kbps as “CD-quality”. It is indeed very difficult to tell the difference, especially with those little plastic ear-phones that come with the NW-HD1. And if you will be using the device while commuting, the train announcer and passing vehicles will most likely drown-out any nuances you might hear. So, you may consider compressing at 256kbps (or 320kbps if it’s an MP3 player) for those rare quiet moments at your desk when you wish to enjoy music.

However, there is a trend that I have noticed more and more individuals following – ripping their CDs in a lossless format. The process of ripping CDs takes a while, so the switching costs of choosing a new and better lossy compression format are enormously high (which is in part why Sony is essentially being forced to support MP3). Instead, why not rip your CDs once into a *lossless* format – build an entire library of all one’s music onto a single HD. Then, if needed, lossy-compress the library onto a portable device. If a better lossy format comes out, a few clicks and your whole music library could be in that new format. No more wasting hours inserting and ejecting CDs. But don’t stop there – if HD space is not a big deal, why compress into a lossy format at all? Why not just use a portable player that can play back in a lossless format? Does such a device exist? Not just one, but two.

The iPod. And its sibling, the iPod Mini.

I’ll admit the iPod Mini, with only 4GB, is not really ideal for a large losslessly compressed library; you will only be able to store at most about 10 CDs. But the 40GB iPod will let you store about 100 CDs. Only a fraction of my collection perhaps, but enough music to enjoy for at least a few months before I get tired of it; at which point a little drag-and-dropping and I’ve got a fresh 100 CD stash in a 9×5cm unit :)

As for the “13,000 songs”, it’s a pure marketing tactic, and a rather low-blow in my book. Indeed, you can store 13,000 songs on the NW-HD1 if you compress them at 48kbps. That is a *very* low bit-rate, producing excruciating “quality” even my hearing-aid wearing, tone-deaf grandfather would raise an eye-brow at. Basically, nobody would use it, but hey, it’s possible and it makes the numbers look good. The truth is, Apple could claim the same thing – any 20GB device that can compress music at 48kbps could claim to hold 13,000 songs (with an average song length of about 4 minutes). But Apple’s numbers use 128kbps – the bit-rate at which music downloaded from the iTunes Music Store is at. In fact, since Connect compresses its tunes at 132kbps, it could be argued that a 20GB iPod stores more EMD music than a 20GB NW-HD1!

So that’s my explanation on audio codecs, quality, etc. Long emails are what happen when asked to explain something I think about day and night – sorry :)

If it’s on the company dime, go with the NW-HD1. But don’t feel guilty about getting an iPod – just say Ando-san recommended it to you!