So, Apple has upped the quality of their high definition movies on iTunes to 1080p. Good news, right? That’s the same quality as Blu-Rays, right? Sadly, iTunes movies still aren’t quite the same quality as their Blu-Ray counterparts. While they can both use the same technology to compress the video, the iTunes files are compressed more heavily to save on size and bandwidth.
Here’s what Iljitsch van Beijnum at Ars Technica had to say after he tested it:
[quote]The iTunes download clocks in at a handsome 3.62GB (where 1GB = 2^30 bytes). It contains a stereo AAC track as well as a Dolby Digital 5.1 track. The video resolution is 1920×798. The BRD is a dual layer BD 50 and has a Dolby Digital 5.1 as well as a DTS-HD track, a number of special features and 30 seconds worth of unskippable copyright warnings […] The BRD retains detail while the iTunes version blows them out. […] Dark gradients are often a problem area with image compression. So it’s no surprise that iTunes stumbles at this point, and shows significant banding. Blu-ray, on the other hand, has no problems.[/quote]
So while you won’t be able to tell the difference between the iTunes content and Blu-Ray content most of the time, there are situations where the heavier compression will show itself. If you’re obsessive compulsive, you’ll probably still be buying Blu-Rays.Here is an example from the movie 30 Days of Night as provided by Ars:
iTunes content is on the left while the Blu-Ray content is on the right. You can see the difference here quite readily, but it probably won’t register as a substantial difference while watching the movie at full speed. For 3.6 GB, you have damn-near the same quality as a 50 GB Blu-Ray movie. Pretty great for those of us who want to try to fit these movies on our fancy high resolution devices. A 12 GB movie wouldn’t be a very fun experience — let alone a full 50 GB Blu-Ray.
Source: Ars Technica