Current challenges to HD movie downloads: ..what HD?
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Every time I see an article about "HD downloads", I can't help but cringe. Hardly anyone understands just how much data makes up a true high definition video, and how that single number can mean more to the visual quality than the resolution does. Because of that, they think the pseudo-HD content being served by Apple is comparable to what you can get over digital cable or satellite -- itself a form of pseudo-HD compared to over-the-air broadcast -- when your typical home broadband connection would scream, cry, and finally just die if you tried streaming real high-def over it.
Have you ever heard the phrase "the only constant in the universe is death"? Here's another one: one can never have enough bandwidth. Despite what companies claim, or even what you think your eyes are showing you, those nifty high definition movie trailers you can get from Microsoft and Apple are just about right for resolution, but compressed at a bitrate of about 4 megabits per second -- which is not HD. DVDs, just to give you an idea of how overly compressed 4mbps is even with an advanced codec like AVC-1/h264, typically run between 6-9mbps. If you've ever paid close attention to just how fast your DSL/cable connection is supposed to be, you'll know that 6mbps is as fast as cable gets in most of the United States, while DSL rolls in at about 3mbps. In reality you'll probably get about half of that, if you're lucky.
Even with a business-tier connection, you're still going to come up well short of being able to stream a DVD-quality video from the Internet, and we're talking about a resolution of 720x480 as opposed to 1280x720 (called 720p for progressive -- about all you'll get with cable and satellite) or 1920x1080 (called 1080i for interlaced -- what you get from NBC/CBS/whoever with an antenna) for the really good stuff. There is little more you need to know about how video compression works than to know that if you have a higher resolution, you need an even higher bitrate to avoid block-style artifacts and ugly color gradients.
With real HD that isn't overly compressed to make room for more than one channel (something even Verizon does with it's fiber-to-the-home service, FioS) you're going to end up coming back to DVDs for a proper comparison. To get DVD quality, you'll want a DVD bitrate. To get HD quality, you'll want (need) HD-DVD/Blu-ray bitrate. I'm sorry to tell you that you're probably talking about 30-40mbps (compared to 5-9mbps for DVD and the 1-3mbps you'll get from Hulu.com or Apple.) In other words, you can simply forget about it. It won't be practical to stream real HD over the Internet unless the United States institutes an aggressive broadband policy that would put Verizon-style fiber in every single home in the country, and even then nobody really knows if the Internet backbone can handle it.
Why? It just wasn't designed that way. Cable, satellite, and over-the-air (OTA) are efficient one-to-many delivery systems where everyone gets the same information. The number of viewers can increase without increasing capacity or delivery streams since everyone is getting the exact same information and it only needs to be sent once. The Internet was designed for point-to-point information exchange, not en masse delivery, and it's darn good at it, but not so good for broadcasting like a megaphone. For streaming video, the server has to send all that data out once for every person watching. 1mbps (Hulu, typical streaming) may be fine for your home connection, but that server is sending out 50mbps for 50 viewers, and that's lower-than-TV definition we're talking about here
Without a total redesign or an aggressive upgrade in bandwidth from the core all the way out to your home, we've already found a use for the Internet that simply isn't practical, and that's HD video delivery that isn't compressed so badly that you might as well kick down the resolution to that of a DVD (or worse, like standard definition TV.) Or -- if you will -- the quality of Hulu and YouTube.
So the reason I'm cringing today is because while the person on Newsvine.com purports to list the challenges with HD movie downloads, they fail to realize that we aren't even talking about actual HD video, but the overly compressed pretender that might be 1280x720, but is a far cry from OTA 1080i. These things currently aren't even in the same league and there's no sign of things changing anytime soon.
April 14, 2008 10:05 PM | Reply