TV output quality

Q: I’ve read everything iLounge has written about the differences in how Apple TV, the iPod classics, the 3G iPod nano, the iPhone, the iPod touch, and the 5th gen iPod handle video out. Because all that information is spread among many different articles, how-tos, and Ask iLounge Columns, I was wondering if you could bottom-line it for me. My question is what the different devices are capable of sending to a TV as compared to HD and DVD. Please don’t use words like 420i, 1080p or whatever. No one cares about those tech-speak numbers.

It is my understanding that the 5th gen iPod is capable of sending sub-DVD quality images to a TV and the Apple TV is capable of sending better-than-DVD quality images to the DVD – but not as good as HD. And the rest of the iPod family is somewhere in between. Are any of the iPods capable of sending DVD-quality images to a TV, given the right hook-up and without an upconverter?

– Alex

A: With the release of the enhanced fifth-generation iPod in 2006, it was considered by many as a “near-DVD quality” solution.

Of course, how “near” is largely dependent upon your source format, and more importantly the aspect ratio of that material (ie, whether it’s in a standard TV format or a widescreen format).

It’s impossible to accurately describe these differences without getting into a bit of tech-speak, but to keep it fairly simple, the idea behind “480p/480i” is simply indicative of what a normal standard NTSC television can output, and represents 480 “lines” of resolution. This corresponds directly to the “640 x 480” resolution of the iPod itself (note the “480” in the second part of the number).

The problem is that 640 x 480 is the resolution only of standard television content (basically what you see on standard broadcast television channels). Most DVDs for movies and even newer TV shows use a widescreen format that is actually 854 x 480 when played from a normal DVD player. You still get 480 lines, but the width is much greater.

This is where the iPod falls short, since it cannot support that full width. As a result, it has to scale down the image, and you end up with less than 480 lines of resolution.

The causes the image to look a bit “fuzzier” on a normal TV if you’re watching widescreen content from your iPod (the actual resolutions end up being 640×352 or 720×404, depending upon the model of iPod and software used to encode the video).

The Apple TV, on the other hand does support High-Definition formats, but only in the lower “720p” (720 lines) standard that is common to some broadcast television channels. HD-DVD and Blu-Ray use a “1080p” (1080 lines) resolution, so the Apple TV does fall short of what you can get from a High-Definition DVD, but not necessarily short of what you would get from a broadcast HDTV source. Note that presently the only way to get High-Definition content onto the Apple TV is to encode it yourself, or subscribe to some of the few podcasts that are encoded in HD resolutions. The iTunes Store does not presently sell any movies in any resolution higher than that supported by the iPod.

So can the iPod actually output “true” DVD quality?  That’s largely dependent upon your definition of the term, since you’re talking about video in a completely different format, so the conversion process from DVD itself is going to be a factor in the overall output quality. It is safe to say, however, that with standard-format TV content, you can encode videos that should be indistinguishable from the original DVD. Widescreen content will suffer slightly due to the decreased vertical resolution, but for most people the difference will not be significant enough to be noticeable on all but the largest TV screens.