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HDMI To Go
MIPS Makes Media Mobile (Kevin Morris)
My setup bears the tell-tale tattoos of early-adopter syndrome. Each signal source plumbed into the cable jungle on the back of the receiver has no fewer than five separate strands – three for component video and two for analog audio. An S/PDIF might add to the bundle with optional digital audio. One input source – the homebrew HTPC has a pasta-like plethora of cables coming out of the sound and video cards – some of which run through a special converter box that switches VGA to Component Video. Fifty expensive component cable-feet away is the now old-school flat-screen monitor.
For those of us who design mobile devices, HDMI is probably best known as the “one cable that replaces that whole mess” in our home A/V systems. In our mobile-design work life, HDMI hasn’t been coming up that often… yet. Fast forward a few nm, however, and it’s easy to visualize walking up to my 1080p flat screen, plugging my smartphone in with an HDMI cable, and watching the HD video clip I captured when I spotted Sasquatch strolling through the supermarket parking lot. For that to happen, however, somebody needs to tackle the problem of putting HDMI capability into our mobile devices – which is exactly what MIPS has just announced. The company says that about a billion pieces of HDMI equipment should be out there by the year 2010, and MIPS aims to have a piece of that market – particularly the mobile piece.
The MIPS marriage with Chipidea has yielded a sudden stream of differentiating technologies. MIPS’s IP offering has dominated the digital living room, and the addition of Chipidea has complemented that offering with the analog counterparts in a way that makes the combination much more than the sum of its parts. More like a product, in fact. In this case, the product is a 65nm HDMI (High-Definition Multimedia Interface) solution aimed at low-power, portable transmit applications. MIPS is going after digital still cameras, camcorders, portable media players, game consoles, and – the big one – mobile phones. They also feel the IP will find a place on the receive end in HDTVs, A/V receivers, and set-top boxes.
Since HDMI is mostly a standard for cables and connectors, the analog/PHY component of HDMI IP is crucial. The folks who brought us HDMI saw a need for a single cable/connector standard that would replace the expensive and confusing mess that’s hanging out behind my media center with a single, very-high-bandwidth cable. HDMI is not designed around a particular digital standard. Instead, HDMI is designed to carry the full, uncompressed video and multi-channel audio resulting from a vast array of compression and transmission standards. Specifically, HDMI defines electrical and mechanical requirements for cables plus electrical signaling specifications. Three connectors (types A, B, and C) are defined with either 19 or 29 pins. Type A is the normal “home style” connector we see most today with 19 pins. Type B is a higher- resolution version with 29 pins that isn’t often seen yet, and type C is a “mini” connector intended for use with mobile devices.
The cabling standards for HDMI primarily address the data throughput that can be achieved. HDMI specifies performance standards that cables must meet, so there is no specific length or materials requirement. The Category 1 standard supports normal definition or high-definition TV, and Category 2 supports resolutions or bit-rates higher than HDTV (like the increasingly popular high-end 120Hz 1080p).
On the electrical front, the standard specifies a TMDS (Transition-minimized differential signaling) channel that carries the actual audio and video (plus some additional) data. Video data (which accounts for the majority of the bandwidth, of course) is transmitted first, and audio and auxiliary data are transmitted during the blanking intervals in the video. The format itself can support video up to 1080p at 120Hz, with audio up to 8 uncompressed channels at up to 192 kHz. There is also a consumer electronics control (CEC) channel that is designed to carry control information between participating components.
On the home front, chipsets that support HDMI burn lots of power and support lots of channels. For portable device use, power, price, and footprint are at a premium, so MIPS produced a focused IP offering that meets the foreseeable performance and feature needs of the mobile market without overblowing the solution and missing people’s power budgets. The MIPS solution includes a PHY (taking advantage of the transceiver expertise of their Chipidea buddies) and a digital controller for both transmit and receive applications.
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