January 18th, 2008
Don't believe the low bit-rate 'HD' lie
Update 6:00PM - Here’s what fake HD video looks like.
Last week at CES, Comcast announced their “HD” video on demand download service over its future DOCSIS 3.0 that allows 4 minute downloads of entire HD movies. Attendees at MacWorld this week were told that disk-based HD formats like HD DVD and Blu-ray are essentially obsolete because you can simply download “HD” movies from your Apple TV 2.0 box on demand. Microsoft started offering HD downloads for the XBOX360 starting in late 2006. You can even watch “HD” videos from ABC right from the web. There are even YouTube competitors that offer user uploaded “HD” content. There’s just one minor little problem, it’s not HD.
As I’ve tried to educate my readers last year with my blog “Why HD movie downloads are a big lie“, these so-called HD movies use very low bit-rates compared to even standard definition DVDs let alone something like HD DVD or Blu-ray DVD. Raw uncompressed 1080p video at 60 frames per second is about 3000 mbps so even HD DVD’s 28 mbps needs to be compressed about 107 to 1 with the H.264 or VC-1 codec. By all reasonable standards this needs to be the minimum bit-rate for acceptable loss in quality on 1080p video.
Updated 4:30PM - Standard definition 480i DVD movies are typically 5 to 8 mbps (megabits per second) MPEG-2 whereas these so-called HD wannabes weigh in at a pathetic 1.5 to 4 mbps of 720p H.264. Apple’s new HD service is capable of 4 mbps which simply isn’t enough to be considered HD. XBOX360 downloads are 6.8 mbps 720p VC-1 so they’re semi-decent borderline HD. Marketing will push the nicer sounding “720p” aspect of the video but they don’t tell you it’s way too compressed to offer good video fidelity. Blu-ray has a maximum bit-rate of 40 mbps while HD DVD offers a maximum of 28 mbps. Over the air broadcasts can be up to 24 19.38 mbps.
Modern video compression codecs like H.264 or VC-1 can hide these compression artifact problems much better than MPEG-2 video compression but there’s only so much it can do. At best you might get away 50% more compression over older compression technology but 1.5 to 4 mbps H.264 will not be better than 8 mbps MPEG-2 under most video complexity requirements. The only time 4 mbps 720p will look better than 8 mbps 480i is when the video on the screen is almost entirely stationary or it’s a low-complexity video such as animation movies. Under most normal circumstances, the low bit-rate 720p so-called “HD” video will be inferior though many companies are betting that consumers won’t know any better.Â
So the bottom line is that so-called “HD” video from Microsoft’s XBOX360 HD download service and Apple’s new Apple TV service or any other web download service is simply not HD by any respectable definition. These companies cannot and should not use the “HD” name with video that is lower fidelity than standard DVD. As for Comcast, there’s not much detail on it but I highly doubt it’s more than 4 to 8 mbps even on DOCSIS 3.0 because its 160 mbps total capacity is divided between 50 to 400 customers. Only FiOS technology with its massive 620 mbps per 32-user capacity and possibly U-Verse (but slower than real time) has sufficient last-mile capacity to deliver true HD movie downloads at the quality of HD DVD and Blu-ray technology.
I’m not saying that you shouldn’t buy these services from Apple, or other services that offer low bit-rate 720p video downloads, but consumers must be aware of the fact that they’re slightly worse than a 1080p up-converted DVD. Microsoft’s XBOX service is border-line HD that is slightly better than DVD but nowhere near 1080i over-the-air HD broadcast quality.
George Ou is Technical Director of ZDNet. See his full profile and disclosure of his industry affiliations.
