Apple’s portable video strategy has come a long way since the fifth-generation iPod was released in 2005, supporting only 320 x 240 video content—roughly the equivalent of TV sets sold thirty years earlier. Today, traditional iPod and iPhone models support near-DVD quality content, while the Apple TV almost demands high-definition video.
Despite the differences between its various devices, Apple has tried to remain fairly consistent with videos available from the iTunes Store: you could be assured that any video purchased from the iTunes Store would play on all of Apple’s devices. While the videos didn’t take advantage of the greater potential of the Apple TV, or a computer with a huge, high-resolution monitor, the choice of the 5G iPod’s upgraded 640 x 480 resolution as a lowest common denominator avoided consumer confusion over whether Apple’s files would play on their devices.
Unfortunately, Apple has changed its approach somewhat with the release of video rental support and the Apple TV 2.0: certain iTunes Store files, specifically movie rentals, don’t work on certain Apple devices. In this second part of our series on iTunes movie rentals, we examine the actual video formats that Apple now uses for its files, and the devices those files will and won’t play on.
Semantics: An Introduction to How Apple Markets its Video Formats and Resolutions
Resolution—or the number of dots that make up an on-screen image, measured in horizontal dots by vertical dots—is critically important in understanding how detailed or ‘defined’ a picture or movie will be. A standard DVD uses a resolution of 720 x 480—enough dots to create images that looked at least little more detailed than most pre-2000 vintage TVs were capable of displaying, and over four times as detailed as the 320 x 240 screens of 2005-2006 iPods could display. Until very recently, most of the video content available on the iTunes Store was encoded in a 640 x 480 maximum resolution, matching the published on-TV output capabilities of the fifth-generation iPod, as well as the rough limitations of standard-definition television sets. Apple called the 640 x 480 resolution “near-DVD quality,” which to be fair was not far off, depending upon the aspect ratio of the source material.
The problem was that with a maximum resolution of 640 x 480, only traditional television content, with its standard-definition TV 4:3 aspect ratio, actually took advantage of the full 480 lines of vertical resolution. Unfortunately, theatrical movies and many newer TV shows use wider screen aspect ratios, which resulted in actual encoding resolutions of 640 x 352 (for 16:9 content) and 640 x 272 (for 2.35:1 content), resulting in encoded files that fell short of standard-definition TV quality, and didn’t make the most of Apple’s near-DVD quality claims, either.
Rather than presenting movie transfers at a resolution lower than their discs were capable of storing, commercial DVDs used a technology called “anamorphic encoding” to make maximum use of their 720 x 480 dots. Anamorphic encoding basically stretches or compresses the width of the stored image to fit the proper aspect ratio. A movie filmed in the 4:3 aspect ratio is recorded at 720 x 480, but compressed to 640 x 480 for display purposes, while a 16:9 movie is recorded at 720 x 480, but stretched to display at 854 x 480. In either case, the important 480-line vertical resolution is preserved so that the result looks acceptable on any TV, and the DVD player should present the image in a way that doesn’t distort the shapes of people or objects on the screen.
Unfortunately, movies encoded in aspect ratios greater than 16:9 (or 1.78:1) create another issue to consider. The most popular of these is the 2.35:1 “Cinemascope” format, which produces an extremely wide screen presentation, and will result in letterboxing—the black bars that appear at the top and bottom of the screen—even when viewed on a high-definition TV. The other important thing to keep in mind is that the image on a 2.35:1 movie is not truly 480 lines—the black bars actually form part of the 480-line image in this case. In other words, a 2.35:1 standard-definition DVD is still encoded using an anamorphic 854 x 480 resolution, but the actual viewable image is going to be around 854 x 356 once you crop the black bars off the top and bottom. This doesn’t change with high-definition DVD formats either—both Blu-Ray and HD-DVD use native 16:9 aspect ratios, and any movies that exceed this aspect ratio are going to be “hard letterboxed,” or presented with the black bars forming part of the 720p or 1080i/p displayed resolution. For that reason, a 2.35:1 movie on HD-DVD or Blu-Ray is actually only going to have a 1920 x 816 resolution for the viewable content—the remaining 264 pixels are generally divided evenly between the black bars at the top and bottom of the image, bringing the total resolution to an actual 1920 x 1080 only if you include the letterboxing.
Since just about every HDTV on the market uses a 16:9 aspect ratio, watching a 2.35:1 movie in its original theatrical presentation will leave the black bars in place, presenting the movie in a way that makes the most of whatever content is on the disc.
Users who zoom in on their images to fill the screen, effectively cropping off the sides of the image, will obviously not gain full advantage of their HDTVs’ resolution, but will find it easier to see fine details, and notice less letterboxing in the process.
More information on how this all works and the optimal video formats supported by Apple’s devices can be found in our Complete Guide to iPod, Apple TV and iPhone Video Formats.
“Standard-Definition” Movie Rental Quality
So with all this in mind, what is the actual quality of the movies that are available today for rental from the iTunes Store? Unfortunately, the answer depends on a number of factors.
As of today, Apple has not updated most of its existing video catalog. Movies that were previously available on the iTunes Store remain available in the same format and quality as before, and there are no differences between the purchased versions and rental versions of these movies other than the FairPlay Digital Rights Management (DRM) wrapper that’s put on the movie: a purchased movie still uses the same “FairPlay 2” technology, whereas a rented movie requires the new “FairPlay 3” to enforce the rental restrictions. In fact, Apple appears to be distributing the exact same source movie from its servers, and simply changing the “wrapper” dependent upon whether the user is renting or purchasing the movie.
As an example, the following is a comparison of the purchased and rented versions of the movie “Enemy of the State” from the iTunes Store:
Note that all of the specifications are identical between the two movies right down to the bit-rate and length, with the only difference being the copyright notice.
The result is that most existing iTunes “library titles” fall short of the quality that one would expect from a DVD. Even 16:9 movies come in at a non-anamorphic resolution of 640 x 352, rather than in a proper 480-pixel-tall presentation. Whether Apple plans to upgrade this older content or not is uncertain, but until this happens, the iTunes Store’s movies aren’t really DVD-quality.
On the other hand, when it comes to “New Releases,” Apple is now starting to use anamorphic encoding for standard-definition videos. In fact, it appears that even “New Release” titles available prior to the rental announcement are being quietly upgraded to anamorphic resolutions. For example, the following shows the specs on a copy of “Ratatouille” purchased in November:
The same movie re-purchased this weekend shows that it is now encoded using the new anamorphic quality settings:
Further, as we’ve already noted above, a rental of the same title reveals that it is essentially the same movie:
Note that the anamorphic resolution still falls short of 480-pixel resolution, because Ratatouille uses a 2.35:1 aspect ratio. As mentioned above, even actual commercial DVDs do not provide a full 480-line viewable image for 2.35:1 videos as the black letterboxing bars form part of the vertical resolution. For comparison, “Blades of Glory” is a 16:9 movie, and therefore shows a full 854 x 480 anamorphic resolution, with an actual resolution of 640 x 480. Apple’s file still falls short of a DVD’s quality, but the presentation is pretty close, lacking only 80 pixels worth of actual detail in width.
This content update is similar in many ways to what happened in September 2006 when the fifth-generation iPod was upgraded to support 640 x 480 videos. At that time, Apple basically revisited their entire video library and upgraded all of the content to 640 x 480—some sloppily with transcoding, but soon thereafter with true re-transfers into higher-quality files. Previous owners of the older 320 x 240 versions, however, did not receive any form of upgrade option, so it seems unlikely that this would be offered this time around either.
It is uncertain how far back Apple will go in terms of re-encoding older titles into the new anamorphic formats. The current changes may be simply to bring all “New Releases” in line in terms of the quality. It should also be noted that although the fifth-generation iPod does not provide support for movie rentals, since it has not received a firmware upgrade to support the new FairPlay 3 DRM, the upgraded purchased content remains fully compatible with the fifth-generation iPod, since despite the anamorphic encoding, this content remains in an “actual” maximum resolution of 640 x 480.
“Standard-Definition” Movie Rental Quality on Apple TV
While movies purchased or rented on a computer with iTunes can be transferred to an Apple TV, the Apple TV also offers the option to rent movies directly. Significantly, you currently can’t transfer movies you rent directly from the Apple TV back into your iTunes library.
Put simply, if you rent a movie on the Apple TV, it stays on that Apple TV until you delete it or it expires. This is in contrast to other types of purchased content such as TV Shows, which automatically sync back to your iTunes library.
For high-definition content, which can’t be displayed on an iPod, this might make some sense. Apple only makes HD content available for rental if you’re using an Apple TV. Since this type of content cannot be rented from iTunes itself, it’s also reasonable that it cannot be transferred back to your iTunes library. When renting a high-definition movie, it is clearly identified as high-definition (possibly also with Dolby Digital 5.1 sound), and you’re explicitly told that you will only be able to watch it on the Apple TV:
The confusion exists only because you can also rent standard-definition content directly on the Apple TV. Such videos are described as being in “Apple TV Widescreen Format” during the rental process, while the Apple TV reminds you that this content can only be played on the Apple TV itself:
By comparison, video content that you purchase (ie, TV Shows) is described as being in the “iTunes” format and clearly indicates that it will also play on iPods and iPhones:
So, does this restriction on transferring Apple TV rented content into iTunes mean that this content is of a higher quality than a movie rented directly via the iTunes application? Does this mean that if you plan to watch a movie on your Apple TV you should rent it directly on the Apple TV?
We wanted to answer this question, and decided to take a look at the rental content on the Apple TV itself. Since there’s no method for transferring rented content from an Apple TV into iTunes, we basically had to crack one open and plug the hard drive into a computer so that we could see what Quicktime would have to say about it. The results were somewhat surprising.
The following is a comparison of two rented copies of “Spider-Man 3”—one copy downloaded from within the iTunes application and the other one downloaded in “Apple TV Widescreen Format” directly on the Apple TV itself:
Other than the DRM headers, which would likely be different based on the rental times alone, the two files are essentially identical, both in terms of resolution, bitrate, overall length, and the actual size of the files themselves. In other words, the Apple TV Widescreen Format and the iTunes Format are, at least for now, going to produce identical results.
We performed the same comparison with several other standard-definition movies, both older “Library Titles” and “New Releases,” and the results were the same. Although one movie’s resolution might differ from another movie’s based on aspect ratio and whether the movies were old or new releases, in every case any given movie we downloaded into iTunes was identical to the version of the same movie downloaded directly onto the Apple TV.
Notably, the movies copied from the Apple TV manually would not actually play in iTunes, but the error message was the same as the one received when manually copying a rented movie from one iTunes library to another—simply that the movie was authorized to play on another computer or device. It appears that this is due to the way the FairPlay 3 DRM works rather than any inherent incompatibility with the movie format itself.
High-Definition Movies on Apple TV
So what about high-definition movies? Well, as Apple’s specifications for the Apple TV clearly show, the maximum actual resolution of the device itself is 1280 x 720, which basically provides 720p HD output. Regardless of whether the device itself is set to 720p, 1080i, or 1080p, the maximum output resolution remains 720p, making higher-resolution settings largely irrelevant at this time.
The movies themselves are more or less what you would expect from a high-definition 720p rental:
A 16:9 movie is encoded in full 1280 x 720, whereas a 2.35:1 “Cinemascope” movie comes in at around 1280 x 534 (as noted above), since the maximum horizontal resolution (ie, width) is still 1280 pixels. As discussed earlier, this is no different in principle from the way high-definition optical discs are currently handling Cinemascope content, and unlikely to be of any practical concern on a 16:9 TV, since the black bars will form a part of the picture anyway. The only users who are likely to notice any difference in quality between a 720p 16:9 and 2.35:1 movie are viewers who prefer to zoom (and thereby crop) their higher-aspect ratio movies, or home theatre enthusiasts with 2.35:1 projectors, and even in this case, the lower-resolution experience will be the same with HD-DVD or Blu-Ray discs, albeit at 1080p versus 720p. In other words, the Blu-Ray or HD-DVD disc’s content will be unmistakably better, but not because Apple is handling encoding in a fundamentally different way than HD optical disc makers.
Summary of Video Formats
The following table summarizes the resolutions and bitrates of the various types of content currently available from the iTunes Store in the three most common aspect ratios:
Conclusions
As of right now, it’s fairly obvious that Apple distributes its video content in only two general formats—“standard-definition” and “high-definition.” Because the company is dealing with the challenges of converting a back catalog of titles for viewing on higher-quality displays, “standard-definition quality” will vary with the title; for the time being, it’s safe to assume that the quality of any given standard-definition movie will be the same regardless of whether and how it is downloaded from Apple TV or iTunes.
The restriction on transferring standard-definition purchases from the Apple TV into the iTunes library appears to be a purely artificial one at this time.
