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(Left) Apple Lightening Digital AV. (Right) Inside, an ARM processor. Now, how can this chip be used for something useful.... (via panic)


The secret behind the inner-workings of Apple’s Lightning Digital AV adapter has been compromised. The folks over at Panic Blog made a discovery this past weekend that revealed the tiny adapter for what it really is: an incredibly small, ARM equipped computer that decodes video out signals from iOS devices to an HDMI format for viewing on larger screens.


The device isn’t one of the highest rated Apple accessories available on the market, though it does manage to do what it is designed for. Unfortunately, the quality of the video isn’t as great as would be expected - Lightning is incapable of transmitting raw HDMI video, but rather outputs an H264 format video, which is then decoded and converted to HDMI format by the adapter. Like many critics of the adapter, the Panic Bloggers underwent a little experiment to try to figure out why the device would not allow a full 1080p resolution output.


The first thing the Panic bloggers did was compare the old dock connector with the new adapter. By turning on “Video Mirroring,” it was found that the old connector was outputting 1080p resolution. However, the Lighting adapter was found to be limited to a 1600x900 aspect ratio. Strange. Next, they did a much simpler quality test by hooking up an iOS device to an HDTV and staring at the screen. Immediately it was noticed that the Lighting adapter’s video signal wasn’t very clean, either - garbled image artifacts appeared around the edges of text. All of this was eerily similar to the type of video quality loss experienced when using Apple’s Airplay device for streaming. After putting two and two together, it was decided that the adapter would be taken apart to find out what was really going on inside. Lo and behold, a secret ARM chip loaded with 2GB of ram was found.


An anonymous Apple engineer eventually came out and explained that the adapter’s SoC kernel is in fact running software based on XNU. The adapter boots into a daemon upon receiving incoming data, decode that data, and outputs it through the A/V connections. Though quality isn’t as great as it can be, the engineer explains that the adapter’s functionality was feasible for the time it was released. The video quality issues are being worked on now. The unknown engineer then went on to point out that, the advantage of the adapter is its ability to output from a Lighting port to any device on the planet, regardless of the video out bus.


Though true HD quality is still lacking in the device, be sure to look out for an upgraded version soon now that the beans have been spilled. And as the folks over at Panic Blog explain, it’s hard to complain about the adapter’s quality and price now that we know it’s essentially a super miniaturized iOS device.