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The Lightning Digital AV Adapter Surprise

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Re: The Lightning Digital AV Adapter Surprise

#61

Post by jfb »

makomk wrote: post #57
cabel wrote: post #11

Earlier quoted context omitted.

In this case, AirPlay is our easier-to-understand way of saying "the results you're getting are exactly the same as when you stream iOS video using AirPlay". (Which is really weird for a video-out dongle! Especially since the former, non-Lightning one did proper video out.) I've tweaked the post to make it clearer that AirPlay isn't _necessarily_ the _exact_ mechanism being used! It could just be H.264 or MPEG or wha…

It's not that weird at all, in a sense. With this mystery cleared up, all the evidence is basically consistent with "Lightning" being just USB 2.0 over a proprietary connector plus some proprietary authentication chips in the cables. There is literally nothing it does that could not be done with a standard micro USB 2.0 connector.

Lightning is much, much, much more sophisticated than the brain-damage that is USB [1].

[1] http://brockerhoff.net/blog/2012/09/23/boom-pins/

Re: The Lightning Digital AV Adapter Surprise

#62

Post by nirvana »

The 30 pin dock had 30 pins so it could put video out directly and things like that.

Lightening is a SERIAL FORMAT with 9pins. So it streams audio and video out in an encoded form.

The AV adapter, need to take that audio and video and turn it into a standardized AV format for the AV plugs.

Now, rather than a lot of odd incompatibilities because Apple added new features to new devices that older docks don't support, we have a common communication format in lightening that should be much more robust going forward.

Apple can add whatever protocols it needs over the serial connection to support future tech, rather than the old way of redefining what some of those 30 pins meant from period to period-- remember the 30 pin connecter started out in a time when there was firewire taking up some of those pins!

People like to ascribe nefarious purposes to Apple or claim apple is "rippng them off" because a small computer that does digital AV conversion costs $30... and they dont' realize that the 30 pin connector didnt' do any conversion of formats was just bringing the signals out to a standard connector. This one actually has to do work, which is why it has a SoC on it.

Re: The Lightning Digital AV Adapter Surprise

#63

Post by nirvana »

DannyBee wrote: post #36
czhiddy wrote: post #33

Earlier quoted context omitted.

The form factor of Lightning is top notch - all of the USB-variants seem terribly designed after using it. Too bad Lighting isn't free-to-license like Firewire was. That said, the design for this AV adapter is puzzling. I wonder what the hardware limitation was that prevented straight digital video out. (# of pins?)

There are definitely not enough pins to do straight pin for pin HDMI through lightning. Of course, if you are going to go to the trouble to do what they did, you may as well bitstream it through the adapter, ...

The answer is that lightening is a general purpose next generation serial format.

This allows them to support different formats in the future, for instance, say when HDMI isn't popular.

The 30 pin connector didn't have HDMI on it at the time it was created and they have repurposed pins over the years regularly.

Here they can have a much less complicated solution-- a standardised serial bus over which they can stream any future protocol they want to support.

It's a lot more future proof.

Re: The Lightning Digital AV Adapter Surprise

#64

Post by mbell »

kalleboo wrote: post #35
mbell wrote: post #22

Earlier quoted context omitted.

> Mostly I'd love to know exactly what this chip/system does, so if anyone here with far more advanced hardware knowledge than any of us have feels up to hacking around, that'd be amazing! :) Its converting an encoded steam to HDMI output. There aren't enough pins on a lightning connector to directly output HDMI and even if it could, you still need a transceiver somewhere (not particularly trivial in terms of space o…

> There aren't enough pins on a lightning connector to directly output HDMI and even if it could, you still need a transceiver somewhere (not particularly trivial in terms of space or power to stuff in the phone). MicroUSB+MHL accomplishes the same thing quite well on the current crop of Android phones. Why Apple chose the method they did is still quite odd.

MHL is an option but it only fixes the number of pins issue. It has the same problem as HDMI out: you need a transceiver capable of multi-Gbit data rates. You also have to get the video output to the transceiver. Its not the easiest thing to do inside a phone, its really not the easiest thing to do when your next phone release is focused on 'thinner and lighter'.

Apple already made a strong commitment to AirPlay, so they already had a focus on building a fast, smooth, low power encoder that could encode the entire screen. Once encoded, the stream is probably only a few Mbit/s, a data rate that can easily be transmitted with single ended protocols like SPI. Almost all SoCs already have multiple SPI buses so no need to change any hardware.

Their solution may seem inelegant to some, but I think it is great. They managed to support a feature with almost zero hardware costs on the core device (depending on how you assign the lightning connector). A feature that I'm willing to bet only a very small % of all users will ever use. That is a big win, not having to dump extra hardware into a device that only 5% of all users will ever activate does great things for your margin and design flexibility.

Re: The Lightning Digital AV Adapter Surprise

#66

Post by DannyBee »

nirvana wrote: post #63
DannyBee wrote: post #36

Earlier quoted context omitted.

There are definitely not enough pins to do straight pin for pin HDMI through lightning. Of course, if you are going to go to the trouble to do what they did, you may as well bitstream it through the adapter, ...

The answer is that lightening is a general purpose next generation serial format. This allows them to support different formats in the future, for instance, say when HDMI isn't popular. The 30 pin connector didn't have HDMI on it at the time it was created and they have repurposed pins over the years regularly. Here they can have a much less complicated solution-- a standardised serial bus over which they can stream…

This isn't an answer, and in fact, supports the opposite of your point :)

It would have been just as easy to use micro-usb 3.0, which had plenty of bandwidth, and do the exact same pin or format conversions.

Standardized serial buses that are less complicated already existed. What exactly do you think USB 3.0 is?

If the only reason for lighting was "a general purpose next generation serial format", then it is definitely a horrible idea.

Of course, none of this (except DRM concerns) answers why they'd not bitstream the format and convert it to HDMI signaling instead of doing the weird crap they did here.

Re: The Lightning Digital AV Adapter Surprise

#67

Post by makomk »

jfb wrote: post #61
makomk wrote: post #57

Earlier quoted context omitted.

It's not that weird at all, in a sense. With this mystery cleared up, all the evidence is basically consistent with "Lightning" being just USB 2.0 over a proprietary connector plus some proprietary authentication chips in the cables. There is literally nothing it does that could not be done with a standard micro USB 2.0 connector.

Lightning is much, much, much more sophisticated than the brain-damage that is USB [1]. [1] http://brockerhoff.net/blog/2012/09/23/boom-pins/

Knowing what we know now that blog post is kind of amusing. Apple's Lightning appears to be less sophisticated than the DHL video out over micro-USB connectors it complains about. It's like Apple said "screw trying to get a proper video out, we'll just cram it all down USB 2.0 and lossily compress the hell out of it to get it to fit, then stick an entire ARM SoC in the adapter to decompress it again" - it's the most kludgy solution imaginable. (I have no idea whether Lightning actually uses USB 2.0, but it seems to be in the same ballpark bandwidth-wise.)

Re: The Lightning Digital AV Adapter Surprise

#68

Post by revelation »

coldtea wrote: post #54
seanp2k2 wrote: post #30

One must wonder why they chose to expend significant R&D to make a complicated, power-sucking adapter for use on a mobile device that provides sub-par output and costs quite a bit more than a "dumb" cable. Maybe I'm missing something, but I feel like Lightning is just the next Firewire without all the usefulness that FW had (low latency, dedicated bus that wasn't USB, lots of pro audio gear that worked with it, abili…

> One must wonder why they chose to expend significant R&D to make a complicated, power-sucking adapter for use on a mobile device that provides sub-par output and costs quite a bit more than a "dumb" cable. And people have answered this convincingly. From comments on TFA: = = = = = The reason behind this stupid expensive solution: It seems that the lightning connector is similar to the thunderbolt connector idea. Wi…

The reason you can't just serialize everything instead of using different pin functions is that its both ridiculously complex and the bandwidth is simply not there. Apparently Lightning can't even serialize 1080p, so they have to do lossy compression. This is not a connector, its an active data corruption stick. And then they even try to hide it by horribly upscaling it to 1080p.

Re: The Lightning Digital AV Adapter Surprise

#69

Post by revelation »

nirvana wrote: post #62

The 30 pin dock had 30 pins so it could put video out directly and things like that. Lightening is a SERIAL FORMAT with 9pins. So it streams audio and video out in an encoded form. The AV adapter, need to take that audio and video and turn it into a standardized AV format for the AV plugs. Now, rather than a lot of odd incompatibilities because Apple added new features to new devices that older docks don't support, w…

People don't realize that the 30 pin connector didn't do any conversion of formats because they don't care. They want a connector, and what Apple delivered is a power-sipping SOC that actively throws information away, given the artifacts seen, and then upscales to 1080p because they didn't even have enough throughput to get lossy compressed 1080p through the bus.

So yes you get your 30$ worth of components but it's horribly inferior to a 5$ adapter you can get for every other connector on the planet. It's a rip off alright.

Re: The Lightning Digital AV Adapter Surprise

#70

Post by makomk »

signed0 wrote: post #12

So instead of just going with USB3 like other phone manufacturers and having native HDMI they created their own interface that results in an a picture display with noticeable artifacts.

I'm not sure they even bothered to create their own interface. All the evidence so far is consistent with Lightning being USB 2.0 OTG plus a few extra pins for a lockout chip bundled into a proprietary connector. (More accurately, the usual multiplexed USB 2.0 and TTL serial that smartphones tend to have.)
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