Constant Flux

I originally wrote this post about a year ago, when I was still playing with Drupal as a blogging platform. It somehow got lost in the conversion to Wordpress. What was gratifying back then was that Charles Stross posted a related talk that he gave a couple of days later. It was nice to know that I was thinking about the same things as one of the best new hard SciFi authors. I’ve updated it to reflect current technology and my better understanding.

I’ve often imagined what it would be like to have a wearable exocortex that could record everything about me.

Heart rate. Blood pressure. Food intake. Exercise. Medication. Everything I see and hear. Total recall. What bitrate could I record data at?

These are today’s hard drive prices (obtained from The Prophecy Shop):

It’s obvious that at the moment, the cheapest per Gigabyte is a 500GB HD. It costs about R1000. Roughly every 18 months, the storage capacity of hard disk drives double. So let’s assume that every 18 months, you buy the cheapest per Gigabyte drive, and that it costs about R1000. By the time you buy the next one, the storage capacity would have doubled.

You therefore have 18 months to fill the first drive:

1.5 years x 365.25 days x 24 hours x 60 minutes x 60 seconds = 47336400 seconds

And since Seagate measures a gigabyte as 1,000,000,000 bytes:

500 x 1,000,000,000 bytes x 8 bits = 4,000,000,000,000 bits

4,000,000,000,000 bits / 47336400 seconds = 84501 bit/s = 84 kbit/s = 10 KiB/s

That’s about 1.5 times the speed of a 56K modem. Since we sleep roughly a third of our lives away, the base bitrate could probably be boosted to about 140 kbit/s (16KiB/s).

When you buy a new drive, you can transfer all the data you have recorded up to that point, and half the capacity of the new drive will still be unused. You’ve paid the same amount, but you’ve got double the capacity. Half of the new capacity is used to store all previously recorded data, and the rest is available for new data storage.

So this is the progression of average bitrates as you buy new drives:

500GB at 140 kbit/s (16 KiB/s)

1TB at 140 kbit/s (16 KiB/s)

2TB at 280 kbit/s (32 KiB/s)

4TB at 560 kbit/s (64 KiB/s)

8TB at 1120 kbit/s (128 KiB/s)

Wikipedia says that the max average bitrate for handheld profile DivX stream is 24KiB/s, compared to about 488KiB/s for full quality. That means we can afford to start recording a live (low quality) DivX feed about three years from now, with plenty of bits for other telemetry.

You have enough bits for biometric data. You can present your medical aid with full details of your heart rate for the last couple of years. Some medical aids already lower your premiums based on your gym usage - they will probably further lower them based on the medical data you provide them with.

You have enough bits to record every click and every keystroke on your PC. This means that it is possible to implement Jef Raskin’s idea that every action ever taken on your PC must be fully undoable.

The interesting thing is that bitrates are rarely constant. When activity is low, bitrates typically drop as well. Audio and video recording both can be done at reduced quality, which would further stretch your recording times.

You don’t have to decide on quality immediately. A high quality recording can later be compressed to use fewer bits at a lower quality. So you record at the highest bitrates possible, and indicate later which events are worth keeping. As time passes, the least important times recorded will slowly lose bits and quality to make space for new recordings, until they fade away completely. Like memories.

So, do you want your life recorded?