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Interview: MHL's Dr. Judy Chen Discusses The MHL 3.0 Specification

Interview: MHL's Dr. Judy Chen Discusses The MHL 3.0 Specification

The MHL (mobile high-definition link) is a way to connect devices like smartphones and tablets to high-definition displays. MHL connections can be found on a number of devices and displays. The latest specification, MHL 3.0, from the MHL Consortium can handle the emerging 4K displays.

To find out about the latest specification, I talked with the MHL Consortium's President, Dr. Judy Chen.

Wong: Please briefly tell us about the MHL 3.0 specification.

Chen: On August 20, MHL announced its latest MHL 3.0 specification to address the latest consumer trends for connecting a mobile device to displays, marking major advancements in the areas of audio and video transmission over an MHL link. With double the bandwidth compared to the previous specification, MHL 3.0 delivers 4K (Ultra HD) resolution and a wider color gamut to create a more brilliant visual experience, solidifying MHL’s growing presence in the living room.


Wong: What’s new with MHL 3.0 versus previous specifications?

Chen: All of the features listed below are new or enhanced features:

  • 4K (Ultra HD): Support of 4K formats up to 2160p30
  • Simultaneous high-speed data channel
  • Improved Remote Control Protocol (RCP) with support for peripherals such as a touch screen, keyboard and mouse
  • Power charging up to 10W
  • Backward compatible with MHL 1 and MHL 2
  • Latest HDCP 2.2 content protection
  • Enhanced 7.1 surround sound with Dolby Tried and DTS-HD
  • Support for simultaneous multiple displays
  • Connector agnostic – uses as few as five pins


Wong: How does your technology work over just five pins?

Chen: Two of the five pins provide charging supply and ground. The charging pin Voltage Bus (VBUS) provides up to 10W of power in MHL 3.0 to charge an MHL source, for example a smartphone or tablet.

One of the key innovations of MHL is that it uses only a pair of pins to carry video, audio content along with the pixel clock using TMDS. Before transmission to the physical pins, the signals are encrypted with HDCP protocol.

The last but not least, one pin is dedicated to transport bi-directional data which includes EDID, HDCP synchronization, reading and writing register settings and sharing device capabilities


Wong: When do you expect the first products to come out with MHL 3.0?

Chen: Release dates are completely up to each manufacturer’s product life cycle but our expectation is that products will appear some time in 2014.


Wong: You mentioned that MHL 3.0 can support multiple monitors, how do you do that?

Chen: Yes, we support multiple monitors, which is new to our specification. A single MHL 3.0 link can support multiple video streams and those independent streams that can be split out to multiple displays (including MHL) via an accessory such as a dock or a dongle.


Wong: Can I use my existing MHL products with MHL 3.0 products once they arrive?

Chen: Yes, all MHL 3.0 devices will be backward compatible to devices supporting the MHL 2.x and MHL 1.x specification.

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