Mobile High-Definition Link or MHL is an industry standard for a mobile audio/video interface that allows consumers to connect portable consumer electronics devices to high-definition televisions (HDTVs) and audio receivers.
MHL was developed by the MHL Consortium, a consortium made up of leading companies such as Nokia, Samsung, Silicon Image, Sony and Toshiba.
The MHL current standard supports up to 4K (Ultra HD) high-definition (HD) video and 7.1 surround sound audio, including TrueHD and DTS-HD, while simultaneously charging the connected device.
MHL specification version 1.0 was released in June 2010. Later on the standard was further developed with the release of the MHL 2.0 specifications.
The first mass market smartphone, equipped with a MHL connector was the Samsung Galaxy SII and it was released in 2011.
MHL has the following features:
Transmission of 1080p uncompressed HD video
Transmission of 8 channel uncompressed audio (e.g. 7.1 surround sound)
Charges the device’s battery via the MHL cable - up to 500mA for MHL 1.0 and up to 900mA for MHL 2.0
High-bandwidth Digital Content Protection (HDCP) support
Remote Control Protocol (RCP) support allows you to use the TV the remote control to operate the MHL mobile device through the TV’s Consumer Electronics Control (CEC) function (must be supported by the TV).
Connector agnostic, requiring as few as five pins
With phones the MHL link is mostly setup on the Micro USB port, which is used for charging and data transmission on most of today’s mobile phones.
The most widely used adapter is the 5-pin Micro-USB-to-HDMI adapter. Initially, these required a separate power source to operate, but the current MHL standard allows for a passive converter without the need of an extra power source.
Samsung developed their own 11-pin MHL microUSB connector, so recent devices, such as the Samsung Galaxy S III, Galaxy Note II and Galaxy S4, require a proprietary 11-pin Micro-USB-to-HDMI adapter. The good thing is that if you already have a 5-pin Micro-USB-to-HDMI adapter, you would only need a new tip to use it with these smartphones.
In August 2013 the MHL Consortium announced the latest generation MHL 3.0 specifications.
MHL 3.0 comes with the following improvements:
Supports 4K (Ultra HD) 2160p30 video thanks to doubling of the bandwidth by using a bi-directional channel
Enhanced 7.1 surround sound with Dolby® TrueHD and DTS-HD
Power charging up to 10W
Backward compatible with MHL 1 and MHL 2
Latest HDCP 2.2 support
Improved Remote Control Protocol (RCP) with support for peripherals such as a touch screen, keyboard and mouse, which can be used to control the device over the MHL connection, allowing for instance to interact with your smartphone via your cars touch-enabled infotainment screen.