Israeli start up Amimon appears to be on the verge of scoring a major win with its WHDI chip sets which claim to be able to send multiple HD signals around a home using MIMO antenna and a 40 MHz wide OFDM carrier, which appears to have come out of the work of 802.11n wi-fi technology.
The company first showed its face in 2006, and demonstrated its chips at the 2007 Consumer Electronics Show. It finally got Motorola to buy shares in the company in March last year, and then signed TV maker Sharp to use the chips in it’s TV sets, and now appears to have lined up Sony and Samsung, along with Hitachi, to include the technology in a standard for multi-room audio, video and control connectivity.
The key behind the Amimon approach is that it begins with barely compressed video, using a lossless compression standard that only halves the signal requirement for wireless transmission when compared to uncompressed video, around 1.5 Gbps for a 1080p signal. It then decides to divide the data stream into those bits which are more important for quality video rendering, and those which are less important, making the distinction, for instance between the (important) luminance bits and the less important chrominance bits, in a bit mapped piece of video. It refers to them as most significant bits and least significant bits.
So it gets away from the traditional approach for taking a video source, putting it through a lossy compression system (which has no idea of the state of the network that it will travel across) then coding the communication channel for modulation and then reversing each step in the chain (See diagram).
Instead WHDI uses a technique called Joint Source-Channel Coding which first prioritizes video components, then applies two separate error correction schemes to the outcome, encoding the most significant bits of the
important components by better error correcting code which means it ends up transmitting that part at a lower rate, then sends the less important video components at a higher rate with a less powerful FEC. The system then opts to send the less vital information across the noisier frequency and uses space-time coding for better protection of the important components. The same type of quality distinction is made in some video codecs such as that used in the Qualcomm mobile TV system, MediaFLO.
A space’time code is a method used in MIMO systems which relies on sending multiple, redundant copies of data in the hope that at least some of them may survive the physical path. The Amimon system requires at least 4 sending antennas. The whole thing is carried on a number OFDM carriers not unlike 802.11n wi-fi and should be able to borrow from the component base for wi-fi.
Much of this ability to break up the importance of video quality bits is already contained in the JPEG2000 compression standard. This uses multiple resolutions or waves of each vertical and horizontal line, and the level of decode resolution that is required can be placed in a important video stream and others in the less important one. It is said that only around 20% of the information needs to be guaranteed to arrive when using JPEG2000 and errors in the other 80% of the code stream will have little visual impact. Perhaps that’s where Amimon got its ideas from.
Now that Amimon has convinced some of the biggest names in the digital home world, this could become a breakthrough technology and by the sound of how rapidly it will be converted into a standard, it looks like these mega-corporations are really behind the system. The group’s intention is to complete the new standard in 2008.
The claim is that WHDI allows secure, encrypted HD video delivery in multiple streams through multiple rooms which can deal with obstructions, such as people and furniture, and maintain superb video quality with less than one-millisecond latency. The latency aspect is important to retain lip and other sound synchronization with video, and Amimon says that other candidates for HD wireless around the home fail on this point, in part due to the latency introduced by decoding compressed video. It also says that other systems fail to automatically adapt to wireless signals when they vary in how much payload they can deliver.
Sony, Samsung and Motorola getting behind a single initiative would mean the support of the world’s two leading flat TV screen builders, along with the dominant US supplier of cable set tops, and result in a coordinated strike on the richest and most developed HDTV market in the world. But this deal doesn’t sound like a slam dunk. Sony and Samsung have been involved in multiple similar technologies, including Wireless HD, which looks out about 3 years to when 60 GHz technologies might be ‘chip ready’ to offer something similar. Back in November 2006 a slew of six of the world’s biggest consumer electronics companies, made up of Sony, Panasonic, Samsung, Toshiba, NEC and LG Electronics formed the WirelessHD special interest group, around technology supplied from SiBEAM.
So for Sony and Samsung at least, this appears to be a reversal, perhaps brought about because a realistically priced chip for WirelessHD is still some years away.
The other two wireless approaches to sending video around a home come from Ruckus Wireless, which uses 802.11 technology and software which manages packet resends when data is lost, and the UltraWideBand efforts of both Pulse~Link, and the WiMedia Alliance.
Tzero and Sigma have both used the WiMedia UWB to push HD video, with Tzero agreeing to step out of the business, after concerns and a court case over Tzero using Pulse~Link patents in its design. Sigma may go the same way, but both focused on multiple compressed HD streams, using perhaps 100 Mbps, and let’s face it, HD being sent around a home uncompressed, feels a little wasteful of spectrum to us right now.
Pulse~Link has been looking for three years for a breakthrough deal with someone, ideally one of the big three which have signed up with Amimon, and have been unable to close out any such deal. Pulse~Link is understood to be working on JPEG2000 encoding for video distribution around a home and is looking at modern FEC systems that can cope with unequal error protection. All this makes us wonder if perhaps Amimon has only solved half the problem. Instead of using 5 GHz unlicensed spectrum for delivery, which could become crowded and interference prone, what about dropping all of its ideas for unequal error protection and the video coding split, and MIMO, and lay them on top of a pulse based UltraWideBand, which has more native carrier capacity, in some kind of unholy alliance with Pulse~Link. But then again, if it has the eyes of Sony and Samsung, then perhaps it doesn’t need any help here.
The only other entrant is Ruckus Wireless, which is a relatively small operation, and which tends to sell devices which have to be subsidized by telcos as IPTV operators, because they are so expensive.
The objective of this special interest group is to take the existing WHDI technology and enhance it to work on such LCD and plasma HDTVs, multimedia projectors, A/V receivers, DVD and BD players, set-top boxes, game consoles (which will give the PS3 a huge edge), and PCs. The group hopes to get a wide variety of chips manufacturers joining the eco-system and will tightly establish compliance so that all the chips are interoperable.
Earlier this month Israeli start-up Celeno showed, a modified 802.11 baseband chip optimized for video it claims can deliver just 34Mbps at the application layer over more than 120 feet, which means that using MPEG compression it could handle multiple HD streams, also using MIMO , beamforming and switching, targeted at $20 to $30 a chip and it looked like it might give Amimon a run for its money. However now that it has Sony, Motorola and Samsung on its side that threat appears to have gone away.
“The development of the new standard will ensure that when consumers purchase CE devices and take them home, they will enjoy a fast, easy and hassle-free wireless connection that delivers the highest quality,” said Dr. Yoav Nissan-Cohen, chairman and CEO of AMIMON. “The WHDI standard’s objective is to enable an enriched customer experience with multi-vendor interoperability.”
Amimon reckons that its chips can cope with a higher signal to noise ratio than competing systems, that other systems are prone to losing Frames, and that the process of re-encoding can sometimes cause existing visual artifacts to get worse, and that they require hardware encode and decode at each end, adding to cost, delay, and more complex and less robust systems and latency, with all the audio problems this creates.