Spaceway uses digital regenerative switching, so it is not at all like typical geosync comm satellites. But you are right, there is nothing about MPEG-4 on the satellite, it could very well be switching MPEG-2 coded video or even IP (its original mission).
The funny thing is that MPEG-4 streams are carried within the same 188-byte packet MPEG-2 transport stream that normal MPEG-2 live video streams use.
It has not been proven to me (and my job includes me looking at this) that MPEG-4 AVC (H.264) encoders can do a better job today at the same bitrate as the highest quality MPEG-2 encoders (i.e. the ones that cost $50,000).
I expect that, like MPEG-2, we will see MPEG-4 encoders doing a better job over time, and I suspect that eventually the best MPEG-4 encoders will be doing a similar quality to the best MPEG-2 encoders at half the bitrate. But that is in the future, especially for HD!
The launch was from 154 degrees W, but my understanding from the Hughes Network Systems site is that the geosynchronous orbital slot will be 103 degrees W. Sorry, these will be North American birds only.
The "killer technology" on the Spaceway birds are their ability to form tight "spot beams" using Ka band (~20 Ghz) downlink signals.
The spot beams are formed using a 1500 element phased array. The array can form as many as 780 downlink spot beams and 112 uplink spot beams across the US. Compare this with a typical Ku-band (~12 GHz) satellite which has a single beam over the entire US.
Spaceway uses digital regenerative switching of up to 10 Gbps, as opposed to the analog transponders of most geosynchronous communications satellites (despite the fact that most of those transponders are used with digital services these days).
Spaceway was originally supposed to provide satellite point-to-point and point-to-multipoint IP connectivity, but that was dropped in favor of providing massive localized HDTV capacity using spot beams.
Unfortunately, Ka band is more sensitive to rain fade outages than Ku band.
New research show greater releases of methane from hydropower:
In a study to be published in Mitigation and Adaptation Strategies for Global Change, Fearnside estimates that in 1990 the greenhouse effect of emissions from the Curuá-Una dam in Pará, Brazil, was more than three-and-a-half times what would have been produced by generating the same amount of electricity from oil.
And it isn't just from the initial load of dead biomass:
Seasonal changes in water depth mean there is a continuous supply of decaying material.
This again shows the risk of non-dense energy sources. Who knows what goes in and out of a massive hydroelectric reservoir. How can you effectively monitor that? What about a massive tidal power installation? Thousands of wind power generators? Square miles of photovoltaic cells?
On the other hand, we know what goes into and out of a nuclear power plant, because the fuel and waste are so dense, and the small amount of gas produced is easilly recovered and monitored.
8-VSB was developed by Zenith and adopted by the "Grand Alliance" in 1994. During this period, 8-VSB was tested with COFDM, and found to be "technically superior." ATSC standardized 8-VSB in 1996, after two years of experience with the modulation technique. DVB-T using COFDM was not adopted until 1997.
COFDM requires more power than 8-VSB for similar coverage, and power bills are a major cost for broadcasters. The higher power would also cause greater interference to legacy analog channels. COFDM may also be less resiliant to impulse noise from appliances than 8-VSB.
On the other hand, COFDM was "out of the box" more resiliant to multi-path problems than 8-VSB, but the newest 8-VSB receiver chips can handle these problems.
In 1999 (after 50 DTV stations were on the air with ATSC/8-VSB), there was a big row by Sinclair Broadcasting about whether the US should switch in whole or part to COFDM, but it was decided that there was already too much investment in 8-VSB equipment.
There is plenty of DVB-S equipment in the US, on the other hand. I operate some myself. Plus there is a rumor that a large US DBS provider will adopt DVB-S2 next year for its near-optimal coding performance.
With regards to NTSC versus PAL, NTSC was developed in 1940, with NTSC-compatible color standards in 1953, but PAL/SECAM didn't come along until 1967.
So you might want to ask why DVB-T and PAL when there were ATSC and NTSC standards already in existance? Euro-centrism?
Nuclear power is the environmental answer because it is the most dense source of energy.
Tidal generators and wind power require huge amount of dispersed equipment. The environmental damage they cause will be spread over a wide area. We already know that wind power actively kills flying animals. I suspect that tidal generators will also be damaging to sea life.
Another example is hydroelectric. Dams are now causing more greenhouse warming due to their emmissions of methane than they save in reduced CO2 emmissions.
Nuclear power is, of course, a dangerous thing if not done carefully. But most non-dense sources of energy are, by their non-dense nature, inherently environmentally damaging.
You are correct that we can feed all the people on the earth if given the will - it is a matter of universal acceptance of capitalism. Hundreds of millions of people have now been brought out of absolute poverty in China and India because of free market reforms since the 1980's.
The real political push for digital TV is that the band can be more fully occupied, allowing a "repack" of channels to free up UHF channels 52 and higher for other uses.
DVB-T for digital terrestrial television broadcasting is a totally different modulation standard than DVB-S, the satellite broadcasting standard.
DVB-T is based on COFDM modulation, which a lot of people think is inherently better than 8-VSB, the modulation scheme for ATSC. But in truth, the newest receivers for ATSC that can handle multiple reflected signals (ghosts) do just about as good a job.
DVB-S is based on single carrier phase-shift modulation, generally QPSK. The new DVB-S2 offers a high quality 8PSK modulation mode as well for higher bandwidth.
There are a handful of US TV stations which have stopped transmitting an analog signal (NTSC), and are digital (ATSC) only. In urban areas, most viewers are on cable or DBS local-into-local anyway, so by only having one broadcast signal, they are saving a big power bill by turning off the analog service.
The satellite (DBS) providers do have "local-into-local" service for local broadcast stations, but often it requires the purchase of a special dish for a "side satellite".
Re:My HDTV Trivails
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Voom No More
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· Score: 2, Informative
Regarding modulation, the most recent demodulator chipsets for 8-VSB now perform just as well as COFDM receive chipsets. They can handle multiple ghosts, pre-ghosts, etc.
But only a small percentage of Americans depend on over-the-air transmission of any kind, most are on cable or satellite, so I don't think you can blame the current state of US HDTV on 8-VSB. I'm not sure HD has caught on anywhere on the planet, including COFDM modulation countries!
HD's problem has been one of inertia and technological mismatch. People have to spend a lot of money to get into HDTV, and while it looks cool, most people haven't been drawn to it (unlike, say, an iPod, which it seems like everyone NEEDS to have, and can be picked up for a few hundred dollars).
The tech mismatch is that over-the-air reception generally needs another box, cable and DBS systems receive HD differently as well. The technical end of getting HD into your set is beyond most people's "technological knowledge or care level".
Moreover, HD content has lagged because of the market lag...chicken and egg.
On the other hand, HD sets are now finally starting to really sell. Look out for the DirectTV offerings on their Ka-band spot-beam satellites. They'll have a lot of virgin bandwidth for HD. Voom got out there about one year too early for the HD set market.
This is yet another in a long line of non-economists saying stupid and ignorant things about development economics.
People in developing countries who use GPL have priced-in the potential costs of loss of their IP rights versus the potential savings from using GPL products or advantages to using GPL products.
Of course, in many developing countries, the concept of IP rights may not even exist...which can be part of the reason they are still "developing".
As someone who has programmed neural networks on massively parallel computers (10s of thousands of nodes), let me say that lack of parallelism is a minor point when PCs are running at speeds 100s of thousands of times faster than neurons.
What artificial neural networks lack is the millions of years of evolution. If you look at brain, it is not a "random learning network," but almost every part is highly specialized and structured.
Artificial neural networks have been a failure as an "end product," but on the other hand the study has taught a generation of neurophysiologists about parallel computation and signal processing techniques so they can understand better how parts of brain work. In that sense, the study has been a success...
I need a small, cheap ($200), and programmable reasonable quality audio record and playback system. I haven't yet seen any references on the Net to someone getting the gumstix + audiostix to work. Do you know of one?
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The good news about Spaceway is that it uses Ka-band, which has a higher gain for the same sized dish.
But Ka is more sensitive to rain fade than Ku...
Sorry, no clue there! I don't do board-level RF design. I just buy LNBs from DawnCo...
19 Mpbs is the standard (ATSC) for US digital terrestrial HD broadcasts. But trust me, HD looks a lot better at 270 Mbps (HDCAM) rates...
Spaceway uses digital regenerative switching, so it is not at all like typical geosync comm satellites. But you are right, there is nothing about MPEG-4 on the satellite, it could very well be switching MPEG-2 coded video or even IP (its original mission).
The funny thing is that MPEG-4 streams are carried within the same 188-byte packet MPEG-2 transport stream that normal MPEG-2 live video streams use.
It has not been proven to me (and my job includes me looking at this) that MPEG-4 AVC (H.264) encoders can do a better job today at the same bitrate as the highest quality MPEG-2 encoders (i.e. the ones that cost $50,000).
I expect that, like MPEG-2, we will see MPEG-4 encoders doing a better job over time, and I suspect that eventually the best MPEG-4 encoders will be doing a similar quality to the best MPEG-2 encoders at half the bitrate. But that is in the future, especially for HD!
The launch was from 154 degrees W, but my understanding from the Hughes Network Systems site is that the geosynchronous orbital slot will be 103 degrees W. Sorry, these will be North American birds only.
The "killer technology" on the Spaceway birds are their ability to form tight "spot beams" using Ka band (~20 Ghz) downlink signals.
The spot beams are formed using a 1500 element phased array. The array can form as many as 780 downlink spot beams and 112 uplink spot beams across the US. Compare this with a typical Ku-band (~12 GHz) satellite which has a single beam over the entire US.
Spaceway uses digital regenerative switching of up to 10 Gbps, as opposed to the analog transponders of most geosynchronous communications satellites (despite the fact that most of those transponders are used with digital services these days).
Spaceway was originally supposed to provide satellite point-to-point and point-to-multipoint IP connectivity, but that was dropped in favor of providing massive localized HDTV capacity using spot beams.
Unfortunately, Ka band is more sensitive to rain fade outages than Ku band.
My money is on nanomechanical quantum computing. Forget all this ultracold gas vapor stuff, it is like vaccuum tubes...
New research show greater releases of methane from hydropower:
In a study to be published in Mitigation and Adaptation Strategies for Global Change, Fearnside estimates that in 1990 the greenhouse effect of emissions from the Curuá-Una dam in Pará, Brazil, was more than three-and-a-half times what would have been produced by generating the same amount of electricity from oil.
And it isn't just from the initial load of dead biomass:
Seasonal changes in water depth mean there is a continuous supply of decaying material.
This again shows the risk of non-dense energy sources. Who knows what goes in and out of a massive hydroelectric reservoir. How can you effectively monitor that? What about a massive tidal power installation? Thousands of wind power generators? Square miles of photovoltaic cells?
On the other hand, we know what goes into and out of a nuclear power plant, because the fuel and waste are so dense, and the small amount of gas produced is easilly recovered and monitored.
8-VSB was developed by Zenith and adopted by the "Grand Alliance" in 1994. During this period, 8-VSB was tested with COFDM, and found to be "technically superior." ATSC standardized 8-VSB in 1996, after two years of experience with the modulation technique. DVB-T using COFDM was not adopted until 1997.
COFDM requires more power than 8-VSB for similar coverage, and power bills are a major cost for broadcasters. The higher power would also cause greater interference to legacy analog channels. COFDM may also be less resiliant to impulse noise from appliances than 8-VSB.
On the other hand, COFDM was "out of the box" more resiliant to multi-path problems than 8-VSB, but the newest 8-VSB receiver chips can handle these problems.
In 1999 (after 50 DTV stations were on the air with ATSC/8-VSB), there was a big row by Sinclair Broadcasting about whether the US should switch in whole or part to COFDM, but it was decided that there was already too much investment in 8-VSB equipment.
There is plenty of DVB-S equipment in the US, on the other hand. I operate some myself. Plus there is a rumor that a large US DBS provider will adopt DVB-S2 next year for its near-optimal coding performance.
With regards to NTSC versus PAL, NTSC was developed in 1940, with NTSC-compatible color standards in 1953, but PAL/SECAM didn't come along until 1967.
So you might want to ask why DVB-T and PAL when there were ATSC and NTSC standards already in existance? Euro-centrism?
Moreover, Thorium can be bred into fertile material, and there is much more Thorium than Uranium.
But maybe fission is a stopgap measure - until fusion is developed.
Nuclear power is the environmental answer because it is the most dense source of energy.
Tidal generators and wind power require huge amount of dispersed equipment. The environmental damage they cause will be spread over a wide area. We already know that wind power actively kills flying animals. I suspect that tidal generators will also be damaging to sea life.
Another example is hydroelectric. Dams are now causing more greenhouse warming due to their emmissions of methane than they save in reduced CO2 emmissions.
Nuclear power is, of course, a dangerous thing if not done carefully. But most non-dense sources of energy are, by their non-dense nature, inherently environmentally damaging.
You are correct that we can feed all the people on the earth if given the will - it is a matter of universal acceptance of capitalism. Hundreds of millions of people have now been brought out of absolute poverty in China and India because of free market reforms since the 1980's.
There has already been a mild turn-around in the hyperactive NGO world view on global trade.
For example, Oxfam recently complained about the EU blocking Chinese textile imports.
Why buy DVDs of Teletubbies when you can get them on VOD from your cable MSO?
The real political push for digital TV is that the band can be more fully occupied, allowing a "repack" of channels to free up UHF channels 52 and higher for other uses.
DVB-T for digital terrestrial television broadcasting is a totally different modulation standard than DVB-S, the satellite broadcasting standard.
DVB-T is based on COFDM modulation, which a lot of people think is inherently better than 8-VSB, the modulation scheme for ATSC. But in truth, the newest receivers for ATSC that can handle multiple reflected signals (ghosts) do just about as good a job.
DVB-S is based on single carrier phase-shift modulation, generally QPSK. The new DVB-S2 offers a high quality 8PSK modulation mode as well for higher bandwidth.
There are a handful of US TV stations which have stopped transmitting an analog signal (NTSC), and are digital (ATSC) only. In urban areas, most viewers are on cable or DBS local-into-local anyway, so by only having one broadcast signal, they are saving a big power bill by turning off the analog service.
The satellite (DBS) providers do have "local-into-local" service for local broadcast stations, but often it requires the purchase of a special dish for a "side satellite".
Regarding modulation, the most recent demodulator chipsets for 8-VSB now perform just as well as COFDM receive chipsets. They can handle multiple ghosts, pre-ghosts, etc.
But only a small percentage of Americans depend on over-the-air transmission of any kind, most are on cable or satellite, so I don't think you can blame the current state of US HDTV on 8-VSB. I'm not sure HD has caught on anywhere on the planet, including COFDM modulation countries!
HD's problem has been one of inertia and technological mismatch. People have to spend a lot of money to get into HDTV, and while it looks cool, most people haven't been drawn to it (unlike, say, an iPod, which it seems like everyone NEEDS to have, and can be picked up for a few hundred dollars).
The tech mismatch is that over-the-air reception generally needs another box, cable and DBS systems receive HD differently as well. The technical end of getting HD into your set is beyond most people's "technological knowledge or care level".
Moreover, HD content has lagged because of the market lag...chicken and egg.
On the other hand, HD sets are now finally starting to really sell. Look out for the DirectTV offerings on their Ka-band spot-beam satellites. They'll have a lot of virgin bandwidth for HD. Voom got out there about one year too early for the HD set market.
another good thing about outsourcing is that the dollar goes so much further in countries like India, so the criminals need to steal less!
I'm not sure that was only funny - it may also be relevant!
This is yet another in a long line of non-economists saying stupid and ignorant things about development economics.
People in developing countries who use GPL have priced-in the potential costs of loss of their IP rights versus the potential savings from using GPL products or advantages to using GPL products.
Of course, in many developing countries, the concept of IP rights may not even exist...which can be part of the reason they are still "developing".
Not just visual cortex, but also lateral geniculate nucleus and probably a half a dozen other visual areas in brain.
As someone who has programmed neural networks on massively parallel computers (10s of thousands of nodes), let me say that lack of parallelism is a minor point when PCs are running at speeds 100s of thousands of times faster than neurons.
What artificial neural networks lack is the millions of years of evolution. If you look at brain, it is not a "random learning network," but almost every part is highly specialized and structured.
Artificial neural networks have been a failure as an "end product," but on the other hand the study has taught a generation of neurophysiologists about parallel computation and signal processing techniques so they can understand better how parts of brain work. In that sense, the study has been a success...
Thee Python jobs can be found here...
I need a small, cheap ($200), and programmable reasonable quality audio record and playback system. I haven't yet seen any references on the Net to someone getting the gumstix + audiostix to work. Do you know of one?