Airplay uses a bunch of hardware h264 encoding technology that we’ve already got access to, so 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.
LIGHTINING TO HDMI FOR MAC SERIAL
Again, it’s just a high speed serial interface. Lightning doesn’t have anything to do with HDMI at all. We did this to specifically shift the complexity of the “adapter” bit into the adapter itself, leaving the host hardware free of any concerns in regards to what was hanging off the other end of the Lightning cable. Contrary to the opinions presented in this thread, we didn’t do this to screw the customer. There is no clever wire multiplexing involved. Lightning is simply not capable of streaming a “raw” HDMI signal across the cable.
He further goes on to explain why the Lightning adapter can’t stream raw HDMI:
There’s a set of kernel modules that handle the low level data transfer and HDMI output, but that’s about it. It boots straight into a daemon designed to accept incoming data from the host device, decode that data stream, and output it through the A/V connectors. The OS on the adapter is so barebones that there are no Unix tools, no launchd for process management: He notes that there’s no AirPlay involved in the entire flow of outputting video, and that the adapter runs a barebones OS, whose only similarity with iOS is the XNU kernel. Today, an anonymous commenter, possibly an Apple engineer, clarified a lot of information about the adapter over at Panic Software’s blog. While it was clear that there was some video decoding being done by the ARM SoC, we didn’t really know the specifics and the exact reason why the adapter wasn’t outputting raw HDMI. Yesterday, we’d told you about the tiny ARM based computer embedded inside every $50 Lightning Digital AV Adapter.
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