The sad and complex state of video out on smartphones

Have you ever you wanted to connect your smartphone or tablet to an HDTV? I tried to do exactly that and discovered that this is a much more complex problem than I could imagine.

My goal was to be able to use my smartphone and tablet as a source for playing video to the TV in our country house. I also had this crazy idea that I would be able to use my phone as a fully fledged computer with an external display and a Bluetooth keyboard.

As I started reading up on the options I got more and more frustrated at how badly documented it all was. So I turned that frustration into this blog post. If you read the comment sections of sites like Engadget you’ll see there is a lot of confusion around this issue. Hopefully this post will clear that up.

Let’s start by reviewing the different solutions available to output video from a smartphone.

SlimPort (http://www.slimportconnect.com/)

SlimPort is a proprietary solution based on DisplayPort made by Analogix, a semiconductor company. SlimPort allows you to output uncompressed 1080p @ 60 hz through “any 5-wire port”, i.e micro USB, typically the only port on all Android devices for the past few years.

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There are SlimPort adapters for all kinds of displays: HDMI, DisplayPort, VGA and so on.

SlimPort claims to be very power efficient meaning it can show content without external power going to the adapter. I could see this being pretty useful if you’re using the phone to show presentations to customers for example, but in most situations you’re likely to want to charge the adapter anyway to not drain the battery. 

Supposedly SlimPort should be able to draw power and even charge your device while showing content but there’s no information available on which displays support this.

As of now the only notable devices that do support it include some devices made by LG such as the Nexus 4 and Nexus 7 2013 edition.

SlimPort is an implementation of the DisplayPort MyDP standard but there doesn’t seem to be any MyDP branded products available.

The SlimPort branding is somewhat unfortunate. Something like “DisplayPort Mobile” would maybe have been better to emphasize its relation to DisplayPort.

MHL (http://www.meetmhl.com/)

The MHL (“Mobile High-Definition Link”) specification is made by a consortium of companies with Samsung and Sony being the most notable. It’s well supported on the device side and almost every single new modern smartphone from HTC, Sony, Samsung and LG supports it.

Just as with SlimPort, MHL connects through a device’s micro USB port and outputs a nice clean uncompressed signal over HDMI. MHL only supports HDMI so don’t expect to see MHL to VGA or DisplayPort adapters (but you can of course get a separate HDMI to VGA adapter) . 

MHL can draw power and even charge your device from your display, but only on displays that supports MHL. TV:s that do support MHL even allow you to control playback on your smartphone through your TV’s remote just as if it was a Blu-Ray or DVD player although I have yet to see this in practice.

Since most people will be using their MHL-enabled smartphone without an MHL enabled TV, most MHL adapters come with a micro USB port so that the phone can be charged while plugged in. Unlike SlimPort, MHL adapters require power and will not display anything unless it can draw power from the TV or is powered via a charger.

There’s two versions of MHL: 1.0 and 2.0. MHL 2.0 supports 1080p @ 60 hz (full HD) while MHL 1.0 maxes out at 1080i @ 30hz.  2.0 is backwards compatible with 1.0, but if you have a MHL 2.0 compatible device (e.g. the Galaxy S4) you should of course make sure you buy a MHL adapter that supports MHL 2.0.

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So far so good, right? 

There’s only one problem. MHL does not define how the pins on the device side should be configured. So in theory every manufacturer can come up with their own version of MHL and still be MHL compatible. 

That being said, all devices initially supported a standard 5-pin setup. Samsung adopted this standard when they launched their first MHL compatible device, the Galaxy S2, but then changed to their own 11-pin setup on the Galaxy S3, S4 and Note II (and will most likely keep that configuration for all upcoming devices). While Samsung have legitimate reasons for the 11-pin setup [1], the sort of confusion and bad will this has created in the eyes of consumers outweighs the benefits. This whole debacle has been well documented at http://www.galaxymhl.com/.

This means that today there are “MHL adapters” and “Samsung MHL adapters” that only work with some Samsung phones. What is the point of a standard such as MHL if you can’t rely on MHL adapters and devices being compatible with each other? It would have been much better for Samsung to completely drop the MHL branding and just called it “Samsung video out” or something similar.

imageOn the display side, MHL is fairly well supported. A completely unscientific check in a few Swedish electronic’s stores show that roughly 1/4 of all TVs support MHL, including plenty of sub €500 TVs. Finding out exactly which TV:s support MHL require a bit of detective work. If you are in the market for a new TV, I’d recommend you take a few extra minutes to confirm that it supports MHL.

MHL is also supposed to support full surround sound, but since it’s impossible to find out which phones support this specific feature it becomes more of an academic discussion.

Mini HDMI

Some phones also have a separate mini HDMI port (notably some Sony phones). There’s not much more to comment on that other than that it’s a dying breed of phones. Since both SlimPort and MHL allow HDMI over micro USB there should be no need for a separate mini HDMI port.

iOS

Apple are happy to sell you their own proprietary $49 "Lightning AV Adapter" that connects to your lightning port on a newer iOS device and converts it into 1080p through HDMI.  There is no mention by Apple if it’s 30hz or 60hz.

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Presumably to simplify the device SoC, the adapter does a lot of processing. This means that the adapter consumes a lot of power (the adapter has its own CPU and 2 GB of RAM). 

Unfortunately, the adapter compresses the data yielding artifacts when shown on an HDTV. There’s also a lot of criticism online about how it’s actually 720p and just scales the picture to 1080p. It’s clear that this adapter is a “hack” from Apple. While it does the job, Apple was forced to make a few compromises on video quality to make it happen.  

These are all fair compromises but it’s unfortunate that Apple are not open about them. When checking the Apple store it’s easy to believe their adapter will allow you to stream a true 1080p video to your HDTV.  Generally, the consumer perception of HDMI is that it outputs a true pixel-by-pixel representation of the source material and Apple has not made it clear that this is not the case.

Another problem with the AV adapter is that if you are using iTunes then iTunes will block you from showing any purchased content through HDMI due to HDCP protection.

Just like SlimPort, the adapter cannot draw power from the display. Fortunately, the adapter comes with a secondary lightning port so that it can be charged simultaneously. But even without being charged it can still show video.

A note on Android and video out

The Android OS allows apps to be scaled to any resolution. This means that Android apps unlike iOS apps take full advantage of any screen size.

This also applies to TV:s and apps are automatically scaled to fit on 16:9 on a 50” TV. In a word processing app where you want as much screen space as possible this is very useful.

But sometimes it becomes a problem. There are lots of use cases when you want to show an app on a TV or projector the way it actually looks on your phone, just like on iOS. For example when you’re at a trade show and want to show off an app on a large display.

This would be very simple to fix by just having a setting that allows you to output video at the same aspect ratio as the phone. Google if you’re reading this, please make this as a setting in Android.

[Edit: There’s an app for that! Requires root and Android 4.2 though]

Summary

It’s insanely confusing that there are no less than three different solutions that all allow a micro USB port to act as a video out port. If you compare the pictures above of the different adapters you will see they all look identical except for the branding.

I’ve seen some tech journalists write that a device supports “video out over micro USB”. What does that even mean? SlimPort? MHL 1.0? MHL 2.0? A new proprietary standard? Sigh. Tech journalists take note and always ask manufacturers exactly how video out is handled.

To add even more to the confusion there’s even a risk that consumers will start equating micro USB with video out. For example, no Motorola devices support either SlimPort or MHL including the Moto X.

It’s also hard to get an overview of what displays and smartphones support MHL. Even the MHL Consortium’s own site is not updated. For example, the LG G2 is supposed to support MHL but is not listed as a supported device on MHL’s website.

That being said, MHL is definitely the market leader and has a lot of traction both on the device and display side. Consumers that are in the market for a new TV or display should definitely make sure its MHL-compatible.

So what does this all mean? Well, despite all the standards it looks like we are back on square one. Consumers will still have to look at what video out option their phone supports and buy an appropriate adapter.

Here’s a quick cheat sheet:

  • If you have a newer “lightning” iOS device (iPhone 5, iPad 4, iPad Mini or iPod Touch 5th gen), get the "Lightning AV Adapter" from Apple
  • If you have an older iOS device, get the old version
  • If you have a Nexus 4 or Nexus 7 get a SlimPort adapter
  • If you have an MHL-supported phone such as the Galaxy S2, HTC One or Xperia Z get a standard MHL adapter
  • If you have a Samsung Galaxy S3 or Note II get a Samsung MHL 1.0 adapter
  • If you have a Samsung Galaxy S4 get the Samsung MHL 2.0 adapter 

Other random questions that are already answered above but that I asked myself before writing this article

If video out is important to me, what device should I get?

Any device that support MHL 2.0 (e.g. the Galaxy S4) or any SlimPort supported device (e.g. Nexus 4). If you don’t care about video quality you could also go for any newer iOS device.

Which one is best of SlimPort and MHL?

Honestly - they are pretty equal. SlimPort is fighting hard to show the value over MHL and it certainly has a few advantages, check the video below for example. Unfortunately for them, MHL now also supports 1080p @ 60 hz.

Why are you writing about video out? Shouldn’t you be writing about wifi or anything else that you usually write about?

Let’s just say there was a rainy day where my wife was sick and I really wanted to connect my shiny new Nexus 7 to my TV and for some obscure reason I ended up spending way, way too much time figuring out how to do that instead of just doing what a normal human being would have done and went to a store and just bought a cable.

Is this another one of those cases where Apple wins because it ignores the standard and creates a proprietary solution “that just works”?

The easiest way to view it is as if each smartphone manufacturer have their own proprietary standard.

MHL and SlimPort both have a lot of advantages over Apple’s solution such as being able to draw power from the TV and output full 1080p @ 60 hz uncompressed. That being said, you can’t beat the simplicity of Apple where there’s exactly one adapter, albeit subpar, that works with all their iOS devices.

Is this a case of Apple screwing customers by coming up with their own standard?

No. Remember that when Apple made the decision to support video mirroring neither SlimPort or MHL had any traction in the market. Choosing MHL would have meant that they couldn’t output full HD and SlimPort was still an untested solution that no one else supported.

If Apple would adopt a standard for video out, which one would they choose? 

Most likely SlimPort. It’s more power efficient than MHL and can output a video stream without external power, just like their current adapter. Apple is also betting hard on DisplayPort already. Reading online it also seems like SlimPort comes without licensing fees which of course make it a cheaper solution.

[1] The 11-pin setup used by Samsung allows the adapter to draw power from the device, removing the need to power the adapter. It also allows the micro USB port to act as USB host. Acting as a USB host lets users plug in a USB mouse or a USB keyboard.

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