Digital video has received a lot of attention lately. Portable video devices, Flash video, Google Video, video in cars, mobile-phone video, the iPod with video, and the rumored full-screen video iPod are attention magnets for blogs and the industry press.

It makes sense. Predicting great things for video seems like the next step in the logical progression of digital media.

The rise of digital audio

The web, back in the days when it was called the "information superhighway", was a big deal because it allowed the mass exchange, search, and consumption of digital text and pictures. Everyone knew that digital information exchange was a Big Thing. Early audio and video technology were available, but they weren't mature or useful enough to matter.

Then the internet's piracy groups discovered a little-known audio compression codec, MP3, developed by a bunch of Germans. Digital music became so popular as a killer app over the next few years, especially during the Napster lawsuit, that it gave the computer and broadband industries a much-needed boom.

Soon, people wanted portable MP3 players, and the market eventually exploded and became mainstream with the iPod. This makes sense too - we've loved portable music since the first cassette Walkman was released in 1979. MP3 players just made portable music better.

We've also had handheld portable televisions since Sony's Watchman in 1982. We've slowly progressed to modern color-LCD units with better reception and battery life. We even have portable DVD players with large flip-up LCDs for less than the price of a video-capable iPod.

But for every person you know with a portable video device, how many more do you know with portable audio devices?

Moreover, for every minute you spend watching video on a computer, how many minutes do you spend listening to music?

The problem with video

Text-based media, such as web pages, newspapers, and magazines, are much more flexible than audio and video because they don't have a fixed timescale. The consumer sets the timescale arbitrarily. If you only want to devote a few seconds to reading a web page, you can just skim over it and still get a useful amount of information.

Video and audio are fixed-timescale media. The content will take a fixed amount of time to consume, and skipping around within it doesn't give a useful summary. Plus, it's more difficult to index, sort, and archive their content automatically with computers.

These aren't big problems for popular audio content because it's mostly music, and most people don't listen to music as a primary activity. It's a background task, used to enhance their primary tasks (such as reading text).

But to get value out of video content, it needs to be your primary activity. Digital video is produced like television: it's designed to be watched while you're not doing much else. You need to pay attention.

This is fine if you're watching TV on the couch. But watching video on a computer is painful: the physical setup isn't optimal, and there are distractions everywhere. (Ding!) I've got mail! (Pop!) New IM from Dan!

The second I get bored of a video, I start browsing web pages. My boringness tolerance is much lower for computer video than for TV, because there are so many easy alternatives on the computer. I can be doing something more interesting with a single click. I'm expected to sit in front of a computer, an active-use device, passively watching a video?

Plus, audio and video production are far more expensive and time-consuming to produce in high quality than text. A single author can write, edit, and publish an excellent article in an evening without much equipment or specific conditions. But producing high-quality audio and video requires multiple people, more time, and specialized equipment with the potential to be very expensive.

Therefore, there's far less good video content than good text content. The boringness tolerance is lower, and the content you're watching is more likely to suck. I would declare that computer video is dead, but it was never really alive.

What about portable video? That's the hot thing now, right?

Well, let's see. Where would you use a portable video device? Not while walking or jogging - that doesn't work very well. (For the sake of the other people on the sidewalk, please don't try this.) And certainly not while driving somewhere. Many people listen to music while working, but unless you want to get fired, I wouldn't recommend doing the same with video. The only realistic application for portable video is passive travel: kids on long car rides with their parents, or commuters with long bus or train rides. But these situations occur much less frequently than the many situations in which portable audio is useful.

Even if you found a use for portable video, the reality of supporting it in hardware is far worse than supporting audio. Video requires a bigger, brighter color screen with far more processing power and storage space. The resulting devices are larger, heavier, and more expensive with less capacity and far less battery life than a similar audio device.

Why does everyone think that this is going to be a big hit?