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Use your iDevice as an extra display for your Mac

182 points| bauerpl | 11 years ago |duetdisplay.com | reply

112 comments

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[+] drinchev|11 years ago|reply
I wonder how they achieve "Zero lag". I've been using similar software ( AirDisplay [1] ) and the lagging is awful.

You have to be certified hardware manufacturer if you want to use the USB connection to transmit any data between the iPad and your Mac [2]. So my bet is they either use WiFi ( which can roughly get 60fps on retina resolution ) or Bluetooth 4. In both cases I think the refresh rate would not satisfy in a lot of cases, e.g. playing a YouTube video through their software on the iPad.

1: https://avatron.com/applications/air-display/ 2: https://avatron.com/support/faq-air-display/#toggle-id-13

EDIT:

I've found more information on their facebook page [3]

> To setup, download and open duet on your Mac (for free) and on iOS.

> Connect your device using a lightning or 30 pin cable. Done.

> No need to worry about firewall settings, Wi-Fi speed or your 802.11n network.

> Duet is secure, simple, and allows you to use your iOS and OS X devices in harmony.

So I guess I was wrong with my bets. Maybe they got a hardware manufacturer license from Apple. Anyway launch is on 16th, so let's see.

3: https://www.facebook.com/duetdisplay/info?tab=page_info

[+] supercoder|11 years ago|reply
My guess would be they're just using the shared documents area .

There's a number of libraries on the desktop that let you access an API to write to the shared documents area. I'd guess they'd just be piping a mp4 feed to this and the iOS would just be reading from there.

[+] iancarroll|11 years ago|reply
There's a working download link in the footer, not sure why.
[+] alexggordon|11 years ago|reply
I've been beta testing duet for about a month now. As a person that travels a lot, it's awesome. The developers have done an incredible job, and have been very responsive in fixing the bugs I've reported to them.

However, a couple of things to note. Firstly, this is lag free, but still not something you should play videos on. I'm not sure what the framerate is, but I'd be surprised if it's over 30fps. I believe this is probably a result of using USB.

Secondly, I never thought I'd say this, but retina is not your friend. On the new iPads, the OS X menu bar is maybe a centimeter tall. Obviously, you can change the resolution, but I like hi-res, and you just see so little when you bump it up (keep in mind the new iPad is only 1024 by 768).

The app is the best it can be, but what I'd emphasize is that most people should really get a second monitor, if that's what they're looking for. I understand you could save some money, but iPads just don't offer enough real estate.

Again, kudos to the devs for doing a great job on the app though.

[+] cooleyandy|11 years ago|reply
This app would be pretty useful when the new bigger iPad comes out.
[+] shurcooL|11 years ago|reply
This isn't the first app that lets you do this, is it? It might be better (or worse) in performance, but the functionality has already been made available in the past, right? Just want to check.

Also, this is neat but I wish it were integrated into OS X + iOS as part of AirPlay. I love AirPlay and want to see it expand to cover all possible permutations (iOS -> OS X screen/audio/both sharing, as well as OS X -> iOS screen/audio/both sharing). That would go well under the Continuity moniker and is something Apple can do well thanks to their control.

Hopefully it's one of the minor new features in next Apple OS updates.

[+] jakejake|11 years ago|reply
I've used an app called Air Display to do the same thing for quite a while, but instead of USB it connects over WiFi - which is convenient, but the refresh rate is slow. I used it mainly to have my chat client on a 3rd screen.
[+] leehro|11 years ago|reply
This is really interesting technically, a couple tidbits I dug up looking in the mac app bundle:

1. There are a couple of OpenGL shaders in the bundle for converting the screen image to HDTV color space/format (420v.fgsh) and some kind of passthrough.

2. They appear to be using x264 to encode the screen with defaults of 1280x720, 1000kbit, superfast preset. (Defaults.plist)

So on the mac side, they're definitely capturing the screen and sending a streaming video. Not surprising, but the curious part is how they manage to get the iPad to stream in that data over USB. I suppose something like HTTP Live Streaming[1] could work. Place small files into the device's Documents area, and they get streamed. It would be awesome if something else was going on here - like a named pipe.

1. https://developer.apple.com/streaming/

[+] spdustin|11 years ago|reply
My guess is it's using Apple's version of RNDIS ... iPad becomes a network peer of the Mac and streams video over that network.

But I don't believe that API is public, so I can't know for sure...

[+] jscheel|11 years ago|reply
I know this is nit-picky, but Duet is not "the first app that allows you to use your iDevice as an extra display". It's not even the second. There's an opportunity here for better copy to differentiate themselves.

Also, I've always thought this would reduce the life of your ipad. Has anyone noticed this?

[+] memeplex|11 years ago|reply
you chopped off this part "...iDevice as an extra display for your Mac using the Lightning or 30-pin cable"
[+] knd775|11 years ago|reply
How? Like the display burning out or something? Maybe something battery related?
[+] Doctor_Fegg|11 years ago|reply
Best part of this: "All iPads."

My iPad 1 is pretty much a paperweight these days (I know, I know, never buy the first version of anything Apple). This could be a great new use for it.

[+] happyscrappy|11 years ago|reply
Seriously. I was going to give away my first gen ipad but due to being so outdated it seemed more of an imposition than a gift.
[+] blaze33|11 years ago|reply
> the first app that allows you to use your iDevice as an extra display for your Mac

I stumbled upon iDisplay.com the other day. Can't recommend anything though, I'm not an apple user, I was looking for ways to replicate my android phone display in my desktop Linux.

[+] teddythetwig|11 years ago|reply
Did you find anything worth using for your use case?
[+] Kluny|11 years ago|reply
Here's the bit I was looking for: http://www.duetdisplay.com/#compatibility

Compatible with all iPads, nice! I have an old iPad 1 lying around that runs very few of the apps I would like to use with it (Office suite and VLC, mostly), so I've been looking for a way to repurpose it, and this might be it.

[+] metanoia|11 years ago|reply
Looks like they changed it to "All iPad hardware with iOS 6 and above". Which means no iPad 1. :(
[+] ripitrust|11 years ago|reply
OK Guys After I installed and launched this MacOS app , it drastically slowed down my chrome and increased the chrome cpu usage. I am guessing something wrong with the duet app display driver.

so if anyone having the same problem like mine, please go to finder, search for "duetdisplay.kext" kernal extension, delete it and reboot your Mac. It should go back to normal.

[+] sathomasga|11 years ago|reply
Well, the app is obviously working for some folks, but in my case it's junk. 13" MBA 2012 OS X 10.10.1 connecting with iPad Mini Retina or iPhone 5s (both iOS 8.1.2) using genuine Apple Lightning cable and direction connection (i.e. no USB hub). Most of the time the iOS app never gets beyond the "Connect to Mac" stage, even though the screen flashes on the Mac indicating new display hardware is available. Sometimes the iOS app gets to the "Launching Duet…" and hangs. Rarely, the iOS app actually becomes a display; however, when that happens my mouse is frozen (in a "stuttering" sort of way). Waste of good money for me.
[+] tluyben2|11 years ago|reply
I have been testing this as well; it is really great for travelling. I put my air 2 on high res and find myself hardly using my normal screen anymore. There are a few bugs but those will be gone soon I reckon; the creators respond fast to mail.
[+] petercooper|11 years ago|reply
Duet is the first app that allows you to use your iDevice as an extra display for your Mac.

What am I missing about this sentence that seems to make "the first" false in the face of things like Air Display?

[+] hboon|11 years ago|reply
It's tethered using lightning cable.
[+] mark_l_watson|11 years ago|reply
Wrong. I have been using my iPad as an extra display for my MacBook Air for about 2 1/2 years using the AirDisplay (getairdisplay.com).

It is odd that this company would place a large lie as the first readable text.

[+] sigjuice|11 years ago|reply
You did not read the whole sentence.

Duet is the first app that allows you to use your iDevice as an extra display for your Mac using the Lightning or 30-pin cable.

This app uses a cable. All the other apps use wifi.

[+] elyrly|11 years ago|reply
I'm happy this application made its way onto Hacker News. First heard it from a founding team member and thought the use-case is immense.
[+] RBerenguel|11 years ago|reply
I've occasionally used AirDisplay when doing minor HTML/CSS stuff (browser on iPad, emacs with impatient-mode on Mac) and it's useful, nice, but when doing heavier lifting lag kills it. I'll definitely be getting it tomorrow, and look forward seeing if I get to use it more or "as often as I did."