This week has to be one of the best moments to warm a pixelnazi's heart ... not because of the new big Retina displays, or the launch of 1080p iTunes and AppleTV, but because of the rare surge of pixel gazing happening around the internet.
You may have heard of the ArsTechnica "smackdown" article already:
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| iTunes left, BluRay right — the perennial red-to-black sensitivity curve strikes again: in the left image, see the early quantization in the top-right edges of the red circle |
But soon after, MacObserver posted a followup, not to dispute that BluRay was better, but taking issue with ArsTechnica's assertion that the difference was marginal and not very noticeable:
In this case, the saturation is noticeably different, and this immediately makes the comparison less accurate in terms of human perception as well as for technical reasons — a pure codec+parameter comparison becomes invalid, as any codec will take different priorities at different parts of the colourspace. Indeed, a saturation shift would also ring alarm bells in terms of the entire colourspace changing, so be wary of irregularities in the hue, brightness and the entire transfer function as well.
One thing we should mention now is that articles like these are going to be very tricky to judge on Windows computers. The second image comparison on the MacObserver article looks totally black:
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| This will be even more crazy-dark if you're reading this on Windows |
ArsTechnica has another good article on what is arguably the more important MPEG upgrade in the new AppleTV, and the other iOS devices in their latest generation:
In the same way that MPEG-2 digital TV decoders are classified as "MP@ML" Main Profile at Main Level for standard definition and "MP@HL" Main Profile at High Level for high definition, there is a step up in capability as the MPEG-4 decoders move from 720p to 1080p standards in the iOS devices.
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| Compare "MP" Main Profile with "HiP" High Profile (courtesy Wikipedia) |
So the new devices support 8×8 transforms, quantization scaling matrices, and separate Cb and Cr QP control. While the iPhone 4S and iPad 3rd gen support "HiP@4.1L", the 1080p AppleTV only supports "HiP@4.0L" — this means a 25Mbps limit on the bitstream you can feed an AppleTV, but a theoretical 62.5Mbps limit to the iPhone 4S and new^3 iPad.
With the whole universe now 1080p compatible, we'll move on to bigger things next time.
UPDATE: Some more microscopic pixel gazing here:
