Giz Explains: Why HD Video Downloads Aren't Very High Def

Yesterday Apple introduced HD TV downloads to the iTunes store, acceptation you can watch Peter be super emo on Heroes at a brittle 720p resolution. That's a college resolution than DVD, and technically, yup, that's HD. There's a bolt though. Like every added video download account touting HD videos, it's all in fact lower superior than DVD. It's all about bitrate: How abundant abstracts is arranged into a file, declared as $.25 per second. Generally speaking, a college bitrate translates into college superior audio and video, admitting superior can aswell be afflicted by codec-the encoding and compression address that was acclimated to accomplish and apprehend the file-so bitrate is not an complete mark of quality, but it's still a actual acceptable indicator. You're apparently a lot of accustomed with this bitrate business if it comes to ripping your CDs. If you boost a CD into your computer, your ripping affairs will ask what architecture you wish and what bitrate you want. A song ripped at a college bitrate will complete better, with added attendance and detail, but it does yield up added space. The aforementioned assumption applies with video, admitting it's in fact a bigger deal, because it's easier to see superior differences in video than it is to apprehend differences in audio. The $.25 accomplish a huge aberration if you get into fast affective being like sports or activity movies-to be frank, they'll attending like splattered, anointed $.25 in awful aeroembolism low-bitrate vids. This blueprint below, expertly crafted by George Ou at ZDNet provides a solid starting point for comparison, with boilerplate bitrates of a lot of agenda video available.

As you can see, approved DVD runs at about 6-8 megabits per second. High-def iTunes content, admitting accepting a college resolution, is bisected that, a simple 4Mbps. Vudu's accepted HD movies is aswell about 4Mbps, if you've got the pipes. Xbox Live Marketplace has the accomplished bitrate-and indeed, generally gets backdrop for its quality-at abutting to 6.8Mbps. On the added hand, standard-def movies on the Netflix Roku box max out at about 2.2Mbps-and are generally delivered in lower qualities because of bandwidth constraints. iTunes accepted def TV shows run about 1.5Mbps. Now, accede that Blu-ray is a beggarly 40Mbps and you see that the analogue of "HD" is al of a sudden appreciably vague. That's a pissload of numbers. What does that mean?

This allegory analysis we ran in February pretty abundant shows you what's wrong: No bulk how alarming MPEG-4 compression-or whatever the codec of the ages is-gets, it can't plan miracles if it's missing bits. It's why Vudu, for instance, is testing out a new closer-to-real-HD service—that they've appear to us has three times the bitrate of any added download account on the market, acceptation it should be abutting to 20Mbps—that will yield hours to bear to your home. But even then, the angle that it would absolutely battling Blu-ray is absolutely laughable. It's not just download casework giving you this watered-down alleged "HD lite", either. Comcast was bankrupt abstraction three HD channels into the amplitude of two, resulting in very shitty searching HDTV, and the digital guys adding a actor HD channels a year aren't abundant better. Now that you accept what makes or break an HD picture—the bulk of data— it's apparently no abruptness to you that the above acumen anybody is peddling subpar HD is bandwidth. HD agreeable is pipe-bustingly huge-a standard-def Battlestar Galactica book on iTunes is 520MB and takes about 15 account to download via a able cable connection. The 720p HD download is 1.4GB and takes 40 account or so for your harder drive to absolutely swallow. The Blu-ray adaptation of the aforementioned ep ability be 10 times that-like 14GB. Putting that in added context, a individual TV adventure would yield up alert the amplitude as the boilerplate dual-layer DVD movie. Right now, we don't accept the broadband basement to abutment it, and who knows if we will? Hell, the humans with the best adventitious of giving us that added bandwidth-the above ISPs like Comcast and AT&T-are accomplishing just the opposite: Implementing acceptance caps that will beggarly beneath HD downloading. The sad affair is, they apparently will not even use the added bandwidth to accomplish their own HD TV channels attending better.

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