
Lightning video adapters feature Apple Secure Boot, run Darwin kernel - rahuldottech
https://twitter.com/nyan_satan/status/1155148789977636864
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bri3d
Previous discussion of XNU/Secure Boot on Lightning video adapters (2013) :
[https://news.ycombinator.com/item?id=5307781](https://news.ycombinator.com/item?id=5307781)
.

This thread has some new information and maybe people will start playing with
these more eventually.

~~~
citrusui
For more context, check out this comment on the Panic Blog:
[https://panic.com/blog/the-lightning-digital-av-adapter-
surp...](https://panic.com/blog/the-lightning-digital-av-adapter-
surprise/#comment-16841)

~~~
stefan_
Don't drink the kool-aid. An adapter that destructively compresses the signal
is an unexpected and unmitigated disaster, not some cool quirk of Lightning
that makes "the host not care what is hanging off it".

The real reason this abomination exists is because as recently as 2018, Apple
is selling products with a connector that has the equivalent bandwidth of USB
2, not even close to transporting a single 1080p video signal.

~~~
bscphil
Yes - this is really quite astonishing. I imagine any video professional would
be horrified to learn that their _CABLES_ were recompressing their video.
There's never an acceptable reason for that it's really amazing I haven't
heard about it before.

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faissaloo
Why on earth would you need a kernel in your adapter

~~~
bri3d
There are kernels running in almost every piece of peripheral hardware you
own. If you have a modern WiFi chipset, LTE baseband, or GPU it's certainly
running an RTOS kernel. Once you switch to a packet-based protocol with
multiple concurrent tasks (decode, packet receive, link negotiation, etc.), it
just makes sense - either you're implementing timeslicing / scheduling on your
own or you can let someone else do it.

The issue that causes poor video quality isn't that Apple chose to run XNU or
use an SoC for their adapter, it's that they chose to use H.264 at a low
bitrate due to hardware support constraints rather than another encoding
scheme which could offer less lossy video.

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throwaway3627
That's some cool enginerding discovered by gindrenigne. AvE, bigclivedotcom
and EEVblog would be proud!

