Apple’s Lightning Digital AV Adapter

Recently, Panic noticed the odd output resolution and MPEG-like artifacts with the new Lightning digital AV adapter and decided to take a hacksaw to it. They found an ARM processor inside.

Lightning digital AV adapter

image credit: Panic blog

Shortly after, they received an anonymous comment that explains it all:

The reason why this adapter exists is because Lightning is simply not capable of streaming a “raw” HDMI signal across the cable. Lightning is a serial bus. There is no clever wire multiplexing involved. […] 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.

This system essentially allows us to output to any device on the planet, irregardless of the endpoint bus (HDMI, DisplayPort, and any future inventions) by simply producing the relevant adapter that plugs into the Lightning port. Since the iOS device doesn’t care about the hardware hanging off the other end, you don’t need a new iPad or iPhone when a new A/V connector hits the market.

While I understand what they are trying to achieve, I think it’s sad that this new Lightning system can no longer carry the uncompressed HDMI output. Maybe they could have streamed the raw video output in a format close to what HDMI expects, then have the adapter add headers and trailers to the data, but that would still be tricky since the system needs to stop sending frames while the adapter is doing its work. And what about HDCP?

Just one of the many tradeoffs that engineers need to make.

Advertisements

6 comments on “Apple’s Lightning Digital AV Adapter

  1. Dnstje Appel says:

    At the older 30pin HDMi connector, there was no HDCP at all, since my capture card in my pc just show the image from the ipad/iphone screen. I didnt have to activate hdcp (glitch in card) so I was good to go.

  2. Hey Darell. I’m trying to extend the cable on the digital av adapter. Need it to connect my iPhone 5 to my car stereo. Any ideas on what I would need to achieve this?

    • darell tan says:

      a HDMI extension cable perhaps? There would probably be Lightning extension cables sold by third parties, but Apple doesn’t carry such a product.

      • C Rod says:

        If I wanted to cut the wire on the adapter and extend it by adding cable would it be possible? I want the adapter hidden in my dashboard. Looking to hide all the clutter and just have one cable running to my phone from the dash.

        • darell tan says:

          It would probably work reliably only up to a certain length, but personally I wouldn’t risk it. If they were using differential signaling, the cable could be extended further, otherwise it would just introduce loss and it will not work reliably any more.

          I suppose you could try lengthening it and if that doesn’t work out, you could just join the two halves back together.

  3. ast says:

    Irregardless is, of course, not a word.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s