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An analysis of 1080p TV shows recently added to iTunes has revealedthat Apple is using more advanced compression techniques to keepfile sizes from becoming unwieldy. Apple announced on Wednesday that it was adding high-definition 1080p television content to theiTunes Store. The upgraded videos will be supported by the new Apple TV and the third-generation iPad , which packs more pixels than a 1080p television. After comparing relative file sizes and video quality of the 720pand 1080p versions of iTunes content, ArsTechnica reported on Thursday that 1080p versions (1,920 x 1,080 pixels) were on average just1.5 times larger than their 720p counterparts (1,280 x 720 pixels),despite having 2.25 times the number of pixels. The report noted that the limited increase in file size is likelydue to Apple's support support for the High profile for compressionof H.264 videos. New High profile decompression algorithms onApple's devices, including the Apple TV, iPad and iPhone, representan improvement over the Main or Baseline profiles utilized in olderdevices. Based on the tech specs for recent devices, Apple appears to haveintroduced the High profile for H.264 video via its A5 chip. Thethird-generation iPad, iPhone 4S, and the iPad 2 all support adecoder level of 4.1, which sets a maximum bitrate of 62.5Mbps forthe High profile, while the new Apple TV, which sports a single-core A5 processor , has a maximum level of 4.0 (25Mbps). By comparison, theA4-equipped iPhone 4 and Apple TV support H.264 video with a Mainprofile at level 3.1 (14Mbps). Report author Iljitsch van Beijnum went on to note that, in somecases, the 1080p version of iTunes TV shows was "pretty muchindistinguishable" from the 720p version, though some shows andscenes did show noticeable improvement with the higher resolution.For instance, van Beijnum found that an episode of The Big Bang Theory didn't always show improvements with the 1080p version, though aside-by-side comparison of one particular frame did reveal improvedclarity and detail. The 1080p file size for the episode was 856MB,compared to 743MB for the 720p version. We are high quality suppliers, our products such as China Vickers Pump , China Hydraulic Pump Spare Parts for oversee buyer. To know more, please visits Rexroth Pumps.
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