MHL as we know it was first released in mid-2010, developed by a consortium of companies looking to create a small form-factor connection for video and audio output on mobile devices such as smartphones and tablets.
Now an industry standard, MHL uses an adaptation of HDMI data in order to offer as many AV features in common with commercially available displays and hi-fi receivers as possible, but requiring as few as 5 pins to achieve a link.
The MHL standard only defines the method of pushing HDMI data around - it doesn't define a specific plug or socket type. This means that MHL can be enabled on virtually any data port, which can lead to some confusion. A USB connector in one device might be MHL compatible, but the same socket in another device may not be.
Knowing if your device is MHL compatible will require a check of the product manual, and then some investigation to see what connector type it needs. It could require a brand-specific adapter only available from the original manufacturer.
By far the most prevalent implementations of MHL have come from Samsung, who have regularly enabled MHL on their smartphones, tablets and phablets. We'll talk more about Samsung's MHL shortly, as that's the only type of MHL that Cable Chick stocks at time of writing.
There are three versions of the MHL standard, and two distinct sets of features. The older versions, 1 and 2, have fairly straight-forward HDMI specs like 1080p video, 8-channel audio and CEC remote control abilities. The very latest standard, version 3, bumps this up considerably to cater for 4K Ultra HD and more.
MHL can take what's being displayed on your mobile device and pipe it through a home theatre system or directly to a TV. Everything from your home screen to video files, music, internet and games can show up on the connected display. It's very handy when you need to make an impromptu presentation, carry around a slideshow, or want to take your TV shows with you on holiday. As long as you have access to a HDMI-ready display and sometimes a USB wall charger to run the adapter, mirroring video and audio can be as easy as plug and play.
Check out our handy chart for a run-down on the major features available from MHL.
The main limitation of any data standard is bandwidth, and the thin little cables that MHL-enabled sockets usually use put a big limit on how long an MHL or connected HDMI cable can be. Three to five metres may be the most you can get out of an MHL link at 1080p. 4K could shorten this to just one or two metres.
Samsung became synonymous with MHL early on by being one of the first-to-market; not just with an MHL implementation, but with a popular device - the Galaxy S2.
Using its data/charge Micro USB 5-Pin socket, the S2 was compatible with MHL adapters for direct connection to TVs, projectors, monitors or even home theatre receivers.
Because the video output abilities offered by MHL were, at the time, superior to what was offered by the iPhone, it became popular for business and travel. This led to a bit of a market flood of MHL cables, many of which were only good for the Galaxy S2.
Because there are no standards to define or limit the socket type used for MHL data, Samsung were able to change the data/charge port on their Galaxy S3 and S4 to an 11-pin Micro USB.
This change allowed for USB On-the-Go and MHL to be used simultaneously, but had the side effect of rendering all the Galaxy S2 MHL adapters worthless for use with newer devices.
The good news was that it was only a movement of the pins, so 11-Pin to 5-Pin adapters were developed to offer a cheaper solution than buying a whole new MHL cable. Another benefit of the change was that later-model S3 and S4 compatible MHL cables didn't require external power to work, and many more Samsung devices like the Note 2 and Tab 3 used the same MHL adapter.
MHL version 3 will still only require 5 pins, even though the new specification allows for Ultra HD 4K @ 30Hz. At the time of writing, there are no products on the market which capitalise on the new MHL v3 features. Our smartphones are another limiting factor, as outputting 4K takes a lot of processing power, so there could be a wait before we see MHL 3 in the wild.
Right now, the latest feature to hit the MHL scene are the passive cables which, instead of requiring external power, are actually capable of charging the source device while they mirror video and audio. The charging features requires that you have a receiver or display with a special MHL-enabled HDMI socket, but they're becoming more and more common. The image below illustrates what to look for in your user guide. Even if you don't have an MHL-ready HDMI socket on your telly, a passive cable can still be used, but may run down the battery.
Samsung aren't the only ones in the MHL game, and more are joining all the time. LG, Onkyo, Roku and HTC have all used MHL, or intend to soon. Without a standard plug, there's no guarantee that they'll be compatible with the Samsung adapters currently available, so be sure to research ahead of time to avoid disappointment.
With Samsung neglecting to include MHL support on its latest devices, such as the Galaxy S6, and with the JellyBean 4.2.2 Android update also breaking MHL compatibility, there is a distinct feeling of abandonment for the standard since this blog 'went to print' in September of 2014.
It's possible that USB 3.1 Type-C will replace MHL in the future, or wireless solutions like Chromecast or Miracast will become the standard. Only time will tell. At any rate, it's more important than ever to check that your device and its operating system can work with MHL before purchasing an adapter.
MHL is a bit of a mess. If you have further questions or comments to help make this blog better - contact us!