Re:MacBook Air
by mattmaroon on Thursday January 17, 2008 @05:57PM
(#100035)
Huh? First you said that uncompressed movies take up about 25gb for 2 hours. Blu-ray movies are generally around 25gb, which leaves the second layer free for extras or whatever.
Then you said that "blue-ray is not uncompressed video (thus, 25GB holds a 2 hour compressed movie)" By your own math they would only take up 12.5ish gb if compressed.
I actually am curious what digital cable uses. It's definitely 720p in my area, and probably compressed, but not highly.
Actually, Matt, you claimed uncompressed movies take 25GB for two hours. Right up here: http://news.ycombinator.com/item?id=99416
What I said is, Blu-ray movies take up on average 25GB with MPEG2 compression. In other words, your original estimate of the size of things was wrong, as was your implication that blu-ray was uncompressed.
The facts on blue-ray: "Discs encoded in MPEG-2 video typically limit content producers to around two hours of high-definition content on a single-layer (25 GB) BD-ROM. The more advanced video codecs (VC-1 and H.264) typically achieve a video runtime twice that of MPEG-2, with comparable quality."
In all likelihood, iTunes is using H.264, or their newest variant. The same as blue-ray. So, in reality, the choice of codec matters a great deal, blue-ray is not uncompressed video (thus, 25GB holds a 2 hour compressed movie), and yes, 1080p is better than 720p.
And it's also worth noting that digital cable, and as far as I know every other on demand HD video service, is also "highly compressed" 720p.