Don’t Be Mean With the Bits

While I may be occasionally described as “fiscally prudent”, I’ve never been one to skimp on space for storage of digital media.

Take, for example, my CD collection. I mentioned ages ago that my music is all MP3-encoded these days. We don’t use CDs anymore because I have a little device which streams music from my Linux server across the wireless network. Things are simple – no more changing disks, no more hunting around to find the right case, no need to find room for 8ft of CDs somewhere in the living room. Plus, it’s just as high-quality and access is instant.

There is a generally-accepted theory that MP3s encoded at 128kbps are “good enough” for most ears. Many portable MP3 players tend to use that bit rate, and that works out fine for 95% of the population (figure pulled completely out of the air there!). 128kbps means that for one hour of music, you will consume 56.25MB of space.

My ears are far from being the hi-definition models fitted to some of my friends, so why do I go for encoding at 192kbps? Ages ago, I sat and did a fairly careful experiment with encoding a range of music, at a variety of bit-rates and found that I could possibly tell the difference between 128kbps and 160kbps in certain bits of music, but I couldn’t be sure. I couldn’t tell the difference between 160kbps and 192kbps at all. So why go for the bit rate that uses of 50% more space than I really needed to?

The answer is because storage is cheap and it always gets cheaper. I’m pretty clued-up on trends within computing and have a rough idea of where things are heading, so using slightly more storage space now is a no-brainer 5 years down the line. My music collection encoded at 192kbps currently uses about 15GB of storage. I could have got that down to 10GB at a lower bit rate, but why bother? Novatech – my local computer supplies centre currently sell a decent-quality 500GB Samsung hard drive for a shade under £52 including VAT. It’s not hard to work out that the extra 5GB would cost just 52p at those rates.

And this leads me onto the main reason I started this blog entry: home movie files. I bought a Canon HV20 camcorder just before Lucy was born and it is just brilliant. In one tiny, hand-held unit, it records some great quality HD footage that can be easily edited on my PC (that’s a blog post for a different day). It’s an HDV model, which means that it uses tapes in the camcorder and footage is transferred to the main PC via a firewire cable.

In camera, the data is recorded at 25Mbps (which is actually using lossy compression), and this data rate applies when you transfer the footage to the computer. That means it “costs” 11GB per hour of video to store on a disk. This data is monumentally precious to us though – there is absolutely no replacing it should something fail. That’s why things are backed-up everywhere.

To start with, no footage shot on a tape is ever erased or recorded-over. Tapes are very cheap these days – a ten pack of decent Sony tapes is just £13. I keep full tapes at work (which is likely to be a very safe place indeed), and £1.30 for long-term archival is a good price. I also duplicate the footage onto DVDs for extra security – it usually three per tape, but they’re less than 20p each in bulk, so again, who cares? In total, including tape, DVD-R and hard disk storage, an hour of footage costs just over £3 for backup in triplicate.

As I said – don’t be mean with your bits.