Mirroring your mobile device to a TV with MHL or SlimPort technology

Ever wanted to mirror your smartphone screen to your big screen HDTV or other display?

Some smartphones come equipped with MHL or SlimPort, and if yours does, then you are in business. There are some subtle differences between the two however. In this article I'd like to take a deeper look at both the MHL and SlimPort technologies.

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What is MHL?

MHL stands for Mobile High-Definition Link and was developed by the MHL Consortium. The Consortium is made up of various companies which include Nokia, Samsung, Silicon Image, Sony and Toshiba. The latest MHL spec (more on the differences between 1.0 and 2.0 later) supports up to 1080p/60 high-definition video and 7.1 surround sound audio. In addition, the connected device can be charged while connected in some cases.

Before we go on, let's break down what 1080p/60 is. The first part of it, 1080, is taken from 1,920 x 1,080 (the resolution of a high definition display). The cool cats call it 1080 for short. Ya dig? Now, in some cases you might see 1080i or 1080p in reference to displays and resolution. The 'p' stands for progressive scan, and the 'i' stands for interlaced. Each frame of an image on the screen is created in one pass (from top to bottom) for progressive scan, and in two passes for interlaced. Every other line is filled with each pass for the latter technology. The process takes twice the amount of time as progressive, as probably expected. Finally, the '60' in 1080p/60 is in reference to the number of frames per second.

Features of MHL technology

Let's take a brief look at some of the main features of MHL. As mentioned above, the device can (but not always, more on that in a minute) be powered by the television while connected. For MHL 1.0 we're looking at 5 V DC/500 mA, and for MHL 2.0, 5 V DC/900 mA. The mobile device (smartphone or tablet) is connected to the TV set with just one single thin cable. With the built-in Remote Control Protocol (RCP) function of MHL, the connected device can be controlled by the TV's remote.

Again, as mentioned above the technology supports 1080p uncompressed HD video and 8 channel uncompressed audio.

MHL also supports HDCP (High-bandwidth Digital Content Protection), which was developed by Intel Corporation. This is a form of digital copy protection that prevents the copying of digital video and audio while travelling across connections.
There are different types of connectors that will work with MHL. First you have the standard 5-pin micro-USB-to-HDMI adapters which were most popular in the earlier days of MHL. While the physical connection being made is between USB and HDMI it is MHL exclusively that is communicating over the cable. There are also straight up MHL cables which allow consumers to connect an MHL-enabled device directly to an MHL compatible TV. Now commonly there is the 11-pin Samsung Micro-USB-to-HDMI adapter. This newer design supports both USB and MHL simultaneously.

Earlier this year in mid-March Samsung released the Galaxy S4 to support the latest version of MHL, version 2.0. This is the first MHL 2.0 spec device.
MHL 1.0, while it has the claim to "power the connected device," in practice it often slowly drains it instead. MHL 2.0 adapters do not require the extra charging input, although it does help power the device quicker if used. Output from 30hz for MHL 1.0 was ramped up to 60Hz/60fps in the new spec. Allegedly 3D content can now be mirrored too.

What is SlimPort technology?

View attachment 2570 SlimPort technology is not new but it is now being included in newer mobile gadgets and in general it serves the same overall purpose of MHL, to mirror the device to a bigger screen. The first device in the mobile realm to kickoff with SlimPort is Google's Nexus 4. When the new Nexus was first released, many people were fully expecting MHL to be one of the features, but SlimPort technology eased the pain when they saw that MHL wasn't compatible with the phone.

As mentioned, when pitting SlimPort vs MHL (expecially MHL version 2.0) there is very little difference, but many find SlimPort to be much more user friendly for wired mirroring. While MHL does work with a non-MHL supported TV set, it isn't without problems according to many who have tested it. In general, the biggest issue is that the mobile device doesn't get "powered by the TV" as advertised. A second cable, for power, is often required to get things to work.

SlimPort cables also support a wider selection of connections. In general they can connect to DisplayPort, HDMI, DVI, and VGA making almost any "display" fair game for the mirroring process. According to the SlimPort web site, "with DisplayPort, you'll experience an advanced digital link for sending audio and video to your display with high resolutions, up to 4K x 2K at 60Hz."

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