Improved H.264 Compression Holds Down File Sizes on 1080p iTunes Store Content

Ars Technica takes a look at the new 1080p content available on the iTunes Store, showing how a "High" compression profile for H.264-encoded content on the iPhone 4S and new iPad and Apple TV are minimizing the increase in file size needed to move from 720p to 1080p.

itunes 720p 1080p comparison
Comparison of 720p (left) and 1080p (right) video quality in iTunes Store content

In a survey of several titles now available in 1080p on the iTunes Store, the report found that file sizes generally increased by 15-25% over their respective 720p versions, despite the number of pixels more than doubling to reach the higher standard.

The reason that the 1080p versions of the iTunes Store videos can be a good deal better without doubling the file size—or worse—can be found in the tech specs of the new AppleTV and the new iPad. The AppleTV now supports H.264 compression for 1920x1080 resolution video at 30 frames per second using High or Main Profile up to level 4.0, the iPad and the iPhone 4S the same up to level 4.1. The profile indicates what kind of decompression algorithms the H.264 decoder has on board—the "High" profile obviously has some tricks up its sleeve that the "Main" or "Baseline" profiles known to previous devices don't support. The level value indicates how many blocks or bits per second a device can handle.

The report also offers a comparison of video quality between the 720p and 1080p formats on the iTunes Store, noting that the increase in image quality for 1080p content is minor in many cases, but more significant in brighter scenes.

Top Rated Comments

studentmac Avatar
158 months ago
Howaaaarrrd!!!
Score: 34 Votes (Like | Disagree)
theMaccer Avatar
158 months ago
Pic of Penny would be much better.
Score: 18 Votes (Like | Disagree)
SB27 Avatar
158 months ago
The Hidden Side of Apple Value

The press mainly focuses on the hardware, sales figures, etc. What people miss about the value that Apple is delivering to customers can be found in this story. At every turn and in every nook and cranny of the Apple ecosytem, their engineers are finding ways to deliver better bang for the buck. Video compression is just one of thousands of ways that Apple thinks completely differently about the user experience than anyone else. This is why they are a $500B company.

I was also struck while watching the keynote for the iPad by the amount of energy and focus put into iLife and iWork. That stuff is simply amazing for only $4.99 a copy (and with mostly free upgrades).

Yes, we are trapped in a closed Apple ecosytem. I like to think of myself as "happily trapped" given the sheer amount of energy, dollars, focus and excellence being delivered in every aspect of their ecosystem.

I will put the pom-poms down now, but this story prompted a visceral reaction and I felt it was worth noting.
Score: 17 Votes (Like | Disagree)
Mr. Retrofire Avatar
158 months ago
At every turn and in every nook and cranny of the Apple ecosytem, their engineers are finding ways to deliver better bang for the buck. Video compression is just one of thousands of ways that Apple thinks completely differently about the user experience than anyone else.
Not really. Apple use(d) their own H.264-encoder, which produces larger files with worse quality, compared to the open source x264-encoder (the command line version). The picture below shows how efficient the x264-encoder is (just an example):



They should work together with the x264-developers (http://www.videolan.org/developers/x264.html). They know the best settings and encoding strategies [1]. x264 is the H.264-encoder with the best visual quality. Warner Brothers use the x264-encoder to encode commercial BDs.

More info:
Seventh MPEG-4 AVC/H.264 Video Codecs Comparison (http://compression.ru/video/codec_comparison/h264_2011/)

Btw:
Apples uses still BZIP2 and ZLIB, which use 10-20 year old compression algorithms (BWT & deflate), to compress the file system, disk images, installer packages, software downloads (Mac App Store), software updates and so on. The newer LZMA and LZMA2 algorithms are not only faster (decompression), the resulting files require also 30 percent less disk space (faster file transfers (downloads)). Apple does not like & use good compression algorithms.


[1]
http://doom9.org/
http://doom10.org/
http://mewiki.project357.com/wiki/X264_Settings
Score: 9 Votes (Like | Disagree)
Deadman64 Avatar
158 months ago
I downloaded 1080P versions of my movies from iTunes and played them on my system (have a 1st gen aTV with a Crystal HD card for 1080P/DTS content on my 60" Pioneer Elite). Truthfully, I saw little difference between the 1080P and 720P iTunes versions, yet a major difference between my 1080P handbraked encodes and direct Blu-Ray movies.

I think that would be a good comparison.

1080P iTunes/Apple TV vs. a 1080P Blu-Ray.
Score: 9 Votes (Like | Disagree)
luke.mac1 Avatar
158 months ago
noting that the increase in image quality for 1080p content is minor in many cases, but more significant in brighter scenes.

So what they're saying is that the difference between 720p and 1080p in the iTunes store is almost negligible? I mean you can see the difference there on the scaled up image, but I imagine you can't really see it on a small screen. Maybe it will be better on a 27" imac or 50" HDTV.
I still think they should offer a larger, higher quality file size for people who wish to download it... maybe something to select in the preferences section of iTunes...
Score: 8 Votes (Like | Disagree)

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