The Rising Technical Standard (2): MHL



Along with the mature high-definition video display technology, people have higher expectations on audio/video experience today. For consumer electronics (CE) devices and home entertainment products, supporting HD audio/video transmission has become an essential requirement. However, while the tendency of mobile devices’ form factor is smaller and smaller, making a product design embedded HD signal transmission interface has become challenging than ever. Also, the high power consumption of HD signal transmission is also a key element that impact the standby time of mobile devices. With these above situation and the increasing needs of mobile audio /video streaming, the latest mobile HD connectivity technical standard – MHL (Mobile High-Definition Link) is therefore released.

MHL is promoted by the MHL™ Consortium, comprised of five well-known corporations: Nokia, Samsung, Sony, Toshiba and Silicon Image. Currently, it has more than 60 adopter members. Due to the focus of the needs of HD audio /video streaming on portable products, the MHL™ Consortium developed this technology to transfer HDMI signal through an existing micro USB port. As the picture indicated below, we can simply see how this technology works: audio /video content on mobile devices can be transferred to HDTV immediately through a single cable.

clip_image004MHL technology needs only five pins to support up to 1080p uncompressed HD video transmission with 7.1 channel surround sound, while also supports HDCP. In addition, mobile device can use MHL for power charging and increase the standby time. It also allows TV remote control to control the mobile device for audio /video content transmission and display. These kind of simple applied scenarios allow consumer products such as cell phones, TVs and notebooks to gradually adopt the MHL technology. For instance, Samsung, Toshiba and HTC have released their cell phones, TVs or tablet devices respectively that adopt MHL technology within this year.

As we have observed, the increasing demand for HD audio/video transmission is easily recognized. For mobile device vendors, the biggest niche to adopt MHL technology is that they only need a single micro USB interface, and then they can have all MHL features including battery charging and HDMI signal transmission support. No additional space will be required for individual micro USB and HDMI interfaces. Therefore, this well-integrated interface technology has been regarded as a killer application.

As MHL’s Qualified Test Laboratories (QTL), Allion provides certification testing services to help vendor go deep into MHL technology. For more details about MHL and its compelling features, please refer to MHL official website at