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Here's how Apple's Lightning-to-HDMI digital AV adapter probably works
Last week, we shared how the folks at Panic had pulled apart one of Apple's Lightning to HDMI digital AV adapters in an attempt to figure out why it didn't seem to output true 1080p HD video. To their surprise, they found that it contained a tiny computer featuring an ARM processor and 256 MB of memory. They had some thoughts on how the accessory might be working its magic, namely that it could be using AirPlay in some way, but now someone claiming to be an Apple engineer has come forward with what's said to be the official explanation of how it works. Posting to Slashdot, the anonymous individual claims that AirPlay isn't actually being used at all, and that contrary to some speculation the adapter's processor doesn't run a stripped-down version of iOS: What happens here is that we use the same hardware to encode an output stream on the fly and fire it down the Lightning cable straight into the ARM SoC the guys at Panic discovered. Airplay itself (the network protocol) is NOT involved in this process. The encoded data is transferred as packetized data across the Lightning bus, where it is decoded by the ARM SoC and pushed out over HDMI. This setup is apparently future-proof according to the poster, since it's entirely software-driven. Apple engineers are apparently aware that the current implementation leaves something to be desired since it introduces lag and compression artifacts, but the adapter's firmware is supposedly upgradeable and improvements will evidently be made to the compression in future iOS updates. The information coming from this anonymous source lines up pretty closely with what we've been told by David Stanfill, founder of AirParrot and Reflector developer Napkin Studio. Stanfill, who has extensive experience with AirPlay, told us that he "[doesn't] believe that the AirPlay itself is being used here, [but] it certainly seems like the underlying hardware that powers AirPlay mirroring is being used for the AV Lightning adapter." Stanfill concurs that this "also explains the limited resolution support -- keeping costs down and performance up means the higher h264 levels needed to support more pixels likely aren't supported by the SoC employed in the adapter." "This does not seem very forward thinking on the part of Apple," Stanfill added. "If the lightning cable is their solution for the foreseeable future, don't hold your breath on putting that retina iPad full-resolution on your 4K TV in a few years. At least not without heavy MPEG artifacts."
Panic digs into the Lightning digital AV adapter, finds a surprise
The folks at Coda and Unison developer Panic Inc. have a good old fashioned mystery on their hands, and it all revolves around Apple's digital AV adapter for iPhone 5 and iPad mini with Lightning connectors. As they tell it, the Coda crew was recently trying out the accessory for capturing video from iOS devices when they noticed something wasn't quite right -- namely that the maximum resolution capable using the adapter wasn't full 1080p and the video signal didn't seem as pristine as it should have been. This lead Panic to wonder if the adapter wasn't sending a "pure," direct signal via HDMI. Lo and behold, when they literally cracked open the US$49 accessory, they found that it seems to contain what amounts to a dedicated, ARM-based system on a chip (SoC) with 256 MB of RAM. They believe the SoC could be performing something akin to AirPlay streaming from the attached device to the HDMI connector, resulting in the compression artifacts and other quality issues including input lag. Of course, they can't be entirely sure this is what's happening, but all available evidence points in that direction. Why take this approach versus the direct output provided by the 30-pin digital AV adapter? Panic thinks it may have something to do with the Lightning connector not having enough pins to provide true video output, or that Apple wanted to shift as much hardware outside of the iPhone 5 and iPad mini as possible to keep production costs (and weight, and battery drain) down to a minimum. Either way, it certainly is an unusual find and one that anyone planning to output video from newer iOS devices will want to bear in mind.
Apple's new Digital AV Adapter: what it will and won't do
Apple introduced the iPad 2 today and along with it rolled out a few new accessories to accompany its new tablet. One new cable to hit the retail shelves is the Digital AV adapter, which can be used to pipe content from your iOS device to your TV. Not just iPad 2-specific, the adapter is compatible with the iPhone 4, the original iPad and the 4th generation iPod touch (although it is somewhat limited on those devices, see below). One side of the adapter plugs into the 30-pin connector on your iOS device while the other connects to an HDMI cable attached to your HDTV. Right next to the HDMI plug is a second 30-pin connector that lets you charge your iOS device while you are connected to your TV. When you purchase the adapter, don't forget to have a spare HDMI cable as the adapter is packaged alone in its box. Before you grab one of these adapters, take note that there is a major difference in functionality between the iPad 2 and the older iOS devices. The iPad 2 is the only device that supports mirroring and 1080p HD. With the second generation tablet, you can send your apps, presentations, websites and more to your HDTV in full HD. The only exception is movies, which are streamed at 720p. The iPhone 4, iPod touch 4th gen and iPad will only push over 720p-quality slideshows and movies. The adapter will also send over digital audio to TVs that support this feature. The Digital AV adapter will be available for US$40 from the Apple online store and in Apple retail stores when the iPad 2 becomes available on March 11.
Apple's Digital AV Adapter also works with iPhone 4, fourth-gen iPod touch, and first-gen iPad
In case you're wondering whether Apple's forthcoming Digital AV Adapter is worth your $39, you might be pleased to know that said HDMI dongle is also compatible with the latest crop of iOS devices before the iPad 2. This includes the iPhone 4, fourth-generation iPod touch, and even the first-generation iPad. Alas, both movies and slideshows will be capped at 720p output from these older devices, whereas the iPad 2 goes a little further with screen mirroring of up to 1080p -- we're guessing the beastly dual-core A5 chip is what makes the magic happen here, though movie output's also limited to 720p. And hey, we're only a few months away from finding out if the next iPhone will also get some 1080p love, so no pressure on buying this dongle just yet.
