Adam T. Lindsay in a recent blog entry presents some interesting speculation on one way Apple could offer HD content through the iTunes Store without going to a multiple-format sales strategy. The current iPod with Video is not capable of displaying HD video in any format nor of down-sampling HD formats to something it can display. An iPod software upgrade that provides downsampling capability is perhaps theoretically possible (and that's a big "perhaps", buckaroo), but it would be too slow to be useful. (That's probably true of a downsampling capability built into the iTunes software using the computer's processing power to automatically downsample when loading an HD file to an iPod device incapable of handling the full HD resolution.

This leaves Apple with the position video podcasters find themselves in now — required to prepare and offer two versions of their programs, one for HD/Apple TV and one for viewing on iPods. Currently, if you want the option of watching The Merlin Show on either your Apple TV in full HD or on your iPod in 640 X 480, you have to subscribe to two separate podcast feeds. Many have suggested that Apple would have to do exactly the same thing to offer HD movies and TV shows for sale — prepare and offer two different versions.

Adam has come up with a suggestion for a single-file solution which sounds pretty nifty — using the new Scalable Video Coding (SVC) extension for the H.264 video standard to "layer" the additional info for a high-resolution image over the top of a lower-res "base" image. The "base" version would be an automatic fallback for devices like the current iPod with Video, with the more capable devices like Apple TV showing the full HD image. One file would play on both sorts of devices. Adam suggests an update to both QuickTime and iTunes would be required to pull this off (as well as, no doubt, software updates for Apple TV and the iPod), but Apple's control over then entire course of the purchase, download and viewing experience would make this quite possible.

The may not be the solution Apple uses, but it seems to be a solution that would work. And, like Dan Dilger of RoughlyDrafted.com and many others, I think it is time for Apple to make the leap to HD video sales. If this idea from Adam would bring that closer, the CouchGuy would welcome it.