Digital Home DesignLine Blog
Wireless network supports uncompressed video in a compressed world
Maurice Wright
7/24/2008 9:10 AM EDT
Read about the recent development in "Consumer giants rally around Wi-Fi variant" by Rick Merritt of EE Times. Apparently Amimon is making the license fees to use WHDI technology affordable, and the supporters will help develop a new version of the standard that offers a robust content-protection layer that would protect content from any source to any destination.
Now I'm all for wireless video. In a prior job I wrote about the subject quite a lot and Google will find those links if you are interested. I was definitely guilty of flip flopping a couple of times as to whether I thought a wireless link could ever provide whole-house video distribution. These days I'm back on the side that says we will need a wired backbone. But that's not the point of this post. Moreover, even if the WHDI technology is viable, the timeline claimed by Amimon and its supporters is way to aggressive. Again, however, that's not my beef here.
The problem with the WHDI movement is that the concept is fundamentally flawed. The group is pursuing a technology that transmits uncompressed video around the home. They are taking on a far bigger challenge than they should need to. Amimon claims it can transmit an uncompressed 1080p stream " a 3-Gbps stream " around the home.
Why transmit uncompressed video and what do I see wrong with the situation? I don't think there's any reason to try and transmit an uncompressed stream. On its technology page, Amimon lists two reasons for uncompressed transmission. One involves content-protection technology. The content owners have long been happy with the secure HDMI link that moves uncompressed video a short distance between set-top- box and TV. Presumably WHDI would use similar technology and avoid scrutiny from the content community. In reality, the content owners have also endorsed content-protection over compressed links using DTCP (Digital Transmission Content Protection). There is no content-security-centric reason to move uncompressed streams.
Amimon also claims that uncompressed is the only answer because of the sheer number of different video codecs in use. This argument caries a bit more weight. But codec ICs are quickly evolving to support virtually every possible coding scheme. And there is a short list that will handle most any source. Moreover every TV today includes a decoder IC for ATSC HDTV and that's the primary stream of interest.
The problem with an uncompressed stream is simple. Even if WHDI can move one 1080p stream around a home, what about the second, the third, and the fourth? The situation becomes untenable quickly. Indeed, even a wired network can't support whole-house transmission of multiple 1080p streams. The industry needs to refocus on compressed video transmission " whether the network technology comes from Amimon, the 802.11 group, or some other technology base.
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Santhoff
7/30/2008 4:16 AM EDT
The 60 GHz guys and Amimon can claim uncompressed is the way to go but the content coming into my home be it CATV, satellite, DVD, Blu-Ray, UTube, Netflix download, etc is all compressed. Why would I want to take content already compressed, decompress it and send it over an uncompressed link??? It's already compressed why not decompress it at the display I already have a FREE MPEG decoder there? I could send DOZENS of compressed video in the bandwidth of one uncompressed stream.
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MichaelHT
7/30/2008 5:17 AM EDT
I'm with a video compression IC maker, specializing in encoders, and the impression I get in talking to the TV makers and other CE companies is that the word "compression" is evil to the U.S. consumer, and the decision to go uncompressed is as much a marketing reason as a technical one. Never mind that, as Mr. Santhoff just said above, the whole Hollywood and broadcasting industries compress the content just to get it there to the home.
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DuckD
7/30/2008 12:52 PM EDT
whatever, the decompress function is always needed , either in Display side or in settop box side.
two things need to consider:
(1) weather the HD encoder technology still in the dynamic change phase ? if so, Display without encoder will have long life span.
(2) for UWB signal transmission in the home multipath situation, what's the benfits to reduce the BW of the UWB signal in the wireless channel?
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Bowho
7/30/2008 1:35 PM EDT
Amimon claimed that their technology could transmit uncompressed 1080p stream, which is 3 Gbps, over 40 MHz channel at 5GH band. This translates to a spectrual efficiency of 75 bits/s/Hz. Anyone who with a bit communication theory concept would know such technology simply doesn't exist. What Amimon could possiblly do is to deploy a so called Joint Source and Channel Coding (JSCC) technology that compresses the video in a different way that could be "smarter" than standard compression solutions. But it is indeed a compression. So, Amimon's claim of uncompressed video is just a marketing tactic (surprisingly enough, many CE companies are willing to join in such tactic to help confusing consumers). Ironically, if Amimon's solution truely has any merit, it would be lie in its proprietary compression technology, not the wireless technology.
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Rick Merritt
7/30/2008 3:29 PM EDT
To me the bigger question is whether any somewhat or non-compliant version of WiFi for video can gain real traction. Anyone remember Magis?
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ExMagis
7/30/2008 11:13 PM EDT
Check out this company, Amedia Networks. Although in relatively lower profile, they have indeed made real progresses in pursuing wireless video solution. Take look of their website at www.amedia-networks.com
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MichaelHT
7/31/2008 4:32 AM EDT
The most interesting article to be written is about the irony of how compression got to be such a bad word to consumers when the source of all content, Hollywood and the broadcasting industry, relies on it to give consumers their content. It's of course vague to just say "compression", there's all kinds, but if manufacturers that are actually using compression for wireless HD are trying hard to conceal this for marketing reasons, that is a VERY interesting and untold story. I have a feeling it comes down to misinformation and lack of education where HDTVs and CD players are sold: the retail channel. There are still MANY "professional" retail salespeople who claim anything played on a turntable sounds better than the "compressed digital garbage" on iPods, etc.
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Noam Geri
7/31/2008 5:02 PM EDT
As co-founder and VP Marketing of AMIMON, one of the companies behind WHDI, I would like to offer my perspective to the question of compressed vs. uncompressed:
Most sources are indeed distributed to the home in compressed format. The video source device (e.g. DVD player, STB) typically decodes the content and then provides the decoded content to the display in uncompressed format (e.g HDMI).
There are many reasons why the connection between sources to displays rely on delivery of uncompressed video. These include copy protection issues, proliferation of codecs, graphic overlays and support for legacy devices. Furthermore, many important sources are generated locally in uncompressed format such as gaming and PC graphics.
The result is the world we live in: a world where content is distributed to the home compressed or generated in the home uncompressed, and delivered from the decoding device to the display uncompressed. The migration from wired connections to wireless will not change this paradigm, which is why the top CE companies have decided to create a new standard for wireless uncompressed HDTV based on AMIMONs WHDI technology.
For an in depth analysis of compressed vs. uncompressed please visit: http://www.amimon.com/PDF/Compressed_or_Uncompressed.pdf
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mgwright
8/5/2008 8:35 PM EDT
I appreciate all of the thoughtful comments. Rick is certainly correct in pointing out that non-standard approaches could be a probalem in any scenario. And as several of you point out, the video sources are compressed.
But I'd also like to emphasize my main point. Even if a technology could move one uncompressed HD stream, that isn't going to address the wishes of consumers. Indeed I can see the need to support five or six streams. No technology -- wireless of wired -- is going to do that in any other manner than a point-to-point connection. But inherently, consumer want a network scenario. The stream simply has to be compressed. The industry should start there and then figure out the technology solution.
Maury Wright
Site Editor
Digital Home
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MattFell
8/6/2008 1:32 PM EDT
Its likely the solution is a mix of compressed and non-compressed wireless home video. Certainly compression can result in transcoding degradation, but if the downstream codec is ran at a much higher bitrate than the upstream codecs, (say 5x) then transcoding artifacts can be minimized to the point of being imperceptible. Also lower-efficiency codecs can introduce novel coding techniques that reduce latency, which would partially address the latency issue. Regarding gaming, there are psychophysical limits beyond which latency is a factor, but as long as these limits are not violated, then latency is manageable. On the other hand, a system that provides for no compression may be perfectly acceptable in a household in which their is only one TV, or in which the other TVs use wired connections. Ultimately I see possibilities for both uncompressed video, and mildly-compressed video for use-cases where there are more than one wireless video distribution stream in the home.
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crutschow
9/10/2008 4:17 PM EDT
MP3, at the compression rates typically used for downloads, can generally be detected as not sounding as good as uncompressed (CD) audio in blind listening tests on a high quality audio system. That may be one of the reasons that "compression" has a bad reputation.
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aboutjack
5/25/2009 10:43 PM EDT
As a cable replacement technology WHDI is exactly on the right path with its uncompressed approach. An HDMI cable is a passive connector. Period. How/why should a replacement for that cable function with compression? As for those quibbling about the bandwidth limitations on multiple simultaneous such connections, just how many different signals does an HDMI cable carry, please? Oh... one, that's right.
I'm actively developing a client project using a WHDI-based video component system and love the simplicity and ease of implementing a direct unit-to-unit wireless HDMI link with this technology.
One more time, in unison: WHDI is an HDMI cable replacement technology. One cable. One signal.
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UmeshShah
7/2/2009 3:50 PM EDT
Why can't someone come up with a hybrid wired(backbone)/wireless combined with Mesh network to achieve support of uncompressed 3-6 streams among devices? I recall that recently Powerline group has reached multiple gbps over powerline (use this as a backbone) and then overlay 802.11n with Mesh network!
Something tells me that it should be possible.
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