The Official AVS 'Mobile DTV' (M-DTV) Topic! - Page 2

Yes even more opportunity/temptation to trash HDTV PQ ... And just what we need, more idiots on the road watching TV while driving.

Thank you for the update. I am looking forward to this. I will optimistically say it would be neat to see devices for this by Christmas 2009, but as a practical matter I am thinking Christmas 2010.

As I understand it, mobile TV sacrifices definition for more error correction. Could this technology help viewers "on the fringe" who suffer from pixels and dropouts? Could a person hook up his laptop or other mobile tv device to his outdoor antenna and expect better reception than that of a "non-mobile tv?"

YES.....but they may be sending out some sort of 24/7 Mini-News broadcast rather than the main program....
Or a PPV Blu-Ray Viewing Service....we'll just have to wait and see how this evolves....

The bold parts of the quotes below are what concern me.



The first quoted part sure seems to describe an independent channel for the mobile signal(s), which is the way I hope this system is deployed. Since ATSC signals can be broadcast on adjacent channels without the problems of NTSC, it should be easy to add channels to any given broadcast market that were not feasible in the analog era.

The second quoted part is incorrect, in my opinion. Reducing bandwidth of any current DTV services to make room for mobile TV signals will certainly have an adverse impact on legacy equipment. The picture quality will be reduced. At best, advances in ATSC/MPEG encoding that could have been used to improve existing signals might be used for mobile TV signals instead.

Thanks for the updates, Ken.

I will be trying something of an experiment. I took a Zenith DTT901 converter box and put it in my work vehicle today. I know that ATSC doesn't work in motion, but I am in the car most of the work day and I was wondering if this will work for TV audio while I am parked for lunch. Our local stations have news broadcasts from 11AM to 12:30 PM and I usually take my lunch break sometime during that time period. My DTT901 was sitting in my detched garage and wouldn't get much use this winter anyway, so I decided to Velcro it to a location in the car to keep it from shifting around. For power, I had a spare 12 volt DC to 120 volt AC inverter that doesn't get used very often. So that just plugged into a a spare cigarette lighter jack. For audio, I took an MP3 adapter that has RCA jacks and connected directly to the auxiliary input on my in dash AM/FM stereo. The antenna is the questionable part for my right now. I am going to try a spare FM antenna first that is probably just a 1/4 wavelength of wire that terminates to an F connector. My normal work area is less than 20 miles from the transmitters at Shoreview MN. Anyway, what do you guys here think? Will this be an exercise in futility trying to get TV audio while parked? Also, are there any other antennas that I should be trying? The channels that I will be trying to listen to are:

4.1 (32) = 578-584 mHz
5.1 (35) = 596-602 mHz
9.1 (09) = 186-192 mHz
11.1 (11) = 198-204 mHz

Judging from the frequency ranges, I suppose ideally if I had an antenna resonant at about 195 mHz and 590 mHz, thus a 1/4 wave antenna cut to about 196 mHz would be 3/4 wave at 590 mHz. I will try my random wire antenna Monday, but if that doesn't work I will do some more experimenting. Also, I tried looking at the FCC records to determine if each of those are using horizontal polarity, but I couldn't tell from the FCC Database.

Reminds me of when I mounted my Heathkit FM Stereo Tuner in my car when I was commuting to college
back in the late-60's, incl a quick disconnect for home use. Stereo was nearly useless when mobile.

ATSC will work (sorta) when mobile, but it's going to die as you pick up speed and fergetit
when you're on the freeway. It will also suffer from building/overpass signal blockages
and multipath dropouts (multiple antennas help).

Factory AM/FM receiver in my '98 Volvo Wagon has separate amplified FM Antennas
in each rear-side window...like folded dipoles...but both Horiz & Vert Polarization.
[A Vee, like RabbitEars, would also provide Horiz & Vert Polarization Diversity.]
When one antenna is in a null, it is likely the other is still receiving a signal.
But it probably doesn't implement an optimized Maximal Ratio Combiner (MRC),
instead using a simple switch to swap antennas when it detects poor quality.

You might find the fol. ATSC Mobile Test of interest:
http://lrts.gel.ulaval.ca/publicatio...ication_12.pdf

In Brazil's SET-ABERT Test Report, they found that ATSC had only a small amount of degradation
when a "typical" signal (with multipath) was also subject to Doppler in the range of 1-5 Hz and
suffered 8-15 dB SNR degradation for 25 Hz Doppler shift:
See Sec 6 starting pg 213: http://www.set.com.br/artigos/testing.pdf

Australia's FACTS Test Summary (see VU 33 & 34) shows Doppler shift is much higher on UHF:
http://happy.emu.id.au/lab/lectures/...e/dtfsmpte.ppt

and a theoretical paper:
http://itl.knu.ac.kr/member/moon/consumer_Nov_2003.pdf

================================================
New ATSC-M/H waveforms tolerate high Doppler shifts & lower SNRs with improved Error Correction.

I now have two days experience with this. What I have learned so far is that the "random length" wire antenna did not work very well for me. LAst night I switched to a rigid multi-band scanner antenna. I have it inside the vehicle horizontally. I seems to work great on Channels 4 & 5. These are the channels of greatest interest to me since there are newscasts from 11 AM to noon and then noon to 12:30PM. As far as set-up, menus, and channel numbers, that is not a problem for me. I set it up ahead of time, so all I really have to do is use the up down button for channel selection. For example, when I finished listening to Channel 4 this afternoon I tuned it back to Channel 5 and when I turn it on tomorrow between 11 AM and noon I should be all set. I may still do some more antenna experimenting. In as much as I am pretty happy with audio reception on 4 & 5, if I could get an antenna that also receives well on 9 & 11, that would be icing on the cake. For the amateur radio operators here, you might notice that 9 & 11 are actually pretty close to the amateur 220 mHz band. The trouble is, it is actually lower in frequency, thus requiring a long antenna. Perhaps the easiest would be to get a 1/4 wave 2 meter antenna and cut it for 195 mHz.

I just read this paper that said that the ATSC M/H payload data rate is 312 kb/s and the total data rate with minimum FEC is 917 kb/s. Could anyone tell me the payload/total data rate for the current standard system for both HD and SD so I'll have something to compare with? Thanks!

http://wwwcms.grassvalley.com/docs/W...DT-4107M-1.pdf

Unfortunately, that paper doesn't describe the possible rates very well. As it turns out, there are many other M/H payload rates.

The main ATSC data/payload rate is 19.39 Mbps. There are eight possible MDRL (Main Data Rate Loss) rates. They are:

0.917 Mbps
1.834 Mbps
2.750 Mbps
3.667 Mbps
4.584 Mbps
5.501 Mbps
6.418 Mbps
7.334 Mbps

Depending on which MDRL rate is used and how much FEC is used at that MDRL, the M/H payload rate can range from 2.528 Mbps down to 0.154 Mbps.

All of the possible combinations are shown in Table 6.1 and Table 6.2 of the specification.

http://www.atsc.org/standards/a153/A...ansmission.pdf

Ron

Thanks dr1394. Also I was wondering what percentage of mbps are for payload and what percentage of mbps are for error correction with HD (non-mobile) TV. I think I read that for every 188 bytes of payload there are 20 bytes for error correction with HDTV. Is that right?

The symbol rate of ATSC 8VSB is 684/286 * 4500000 = 10.76... Msymbols/s. Note that the use of an integer multiple of 4.5 MHz was used so that 8VSB interferes less with NTSC. Each symbol carries 3 bits (8 levels), so the raw data rate is 32.28... Mbps. A 2/3 rate Viterbi/Trellis convolutional code is used along with the 20 byte Reed-Solomon code for error correction. There's also some synchronization data that takes 312/313 of the payload.

The final payload rate is 2 * 188/208 * 312/313 * 684/286 * 4500000 = 19.392658... Mbps.

Ron

NIT: The low-rate RS-CRC is primarily a parity check for ERROR DETECTION, after the
Trellis/Convolutional Code does its ERROR CORRECTION job.

http://www.broadcastingcable.com/art...hp?rssid=20102

- Trip

No, that's silly. You don't need 20 bytes just to detect errors. That can be done
with a 16-bit CRC. Reed-Solomon is an error correcting code.

http://en.wikipedia.org/wiki/Reed%E2...ror_correction

Ron

Last night, I shoved a 6" twist tie into the coax port of my DTT901 and was picking up the five stations below with green dots beside them:

Not even a blip on the VHFs, though.


That's one of the (many) problems with VHF. Nobody wants to futz with huge antennas. And certainly not for mobile.

Mobile DTV demo this spring

Only broadcasters can deliver this kind of TV

Published Jan. 25, 2010

By Steve Behrens

http://www.current.org/dtv/dtv1002mobile.shtml

Another DTV transition is coming soon, and advocates think it will be a hit with Americans. If broadcasters are lucky, it'll also be a hit with the FCC.

With the commission's Broadband Plan brigade making noises about the rationality and economic payoff of moving TV to wired delivery systems and satellite--freeing up more spectrum for consumers' mobile devices--here's a kind of TV that only broadcasting can transmit: TV received in a moving car.

"You cannot overstate the importance of mobile to broadcasting," said Mark Richer, president of the Advanced Television Systems Committee, at the NETA Conference this month in Las Vegas. Richer's committee put together the DTV standard in 2006 and last October wrapped up the Mobile DTV standard. "The ramifications of going to Mobile are far greater than for the switch to digital."

Washington policymakers will get an eyeful in March or April when the Open Mobile Video Coalition stages a "consumer showcase" on eight stations, including two pubTV channels --Howard University's WHUT and MHz Networks' WNVT in suburban Virginia.

The coalition includes more than 20 commercial TV station groups, including Fox, NBC, Univision, Ion and Sinclair, plus PBS, CPB and APTS.

PBS Chief Engineer Jim Kutzner, active in the Open Mobile Video Coalition promoting the technology, noted at NETA that it's the first time in his career that a new TV standard will move to lower specs. The image is composed of just 416 pixels by 240 lines. But you don't need high-def for the kids in the back seat of a Dodge Caravan.

Participants in the Mobile DTV test in D.C. will try watching on an array of new receiving devices--many of which debuted this month at the Consumer Electronics Show--such as Dell Inspiron Mini 10 netbook computers, Samsung Moment phones, LG mobile TV sets and Valups' Tivit portable receivers that feed portable monitors via Wi-Fi.

Stations will use Harris and Rohde & Schwarz equipment to add the signal to their DTV transmissions.

The showcase isn't a test of the technology, Richer said, but a test of what consumers think of it.

What will viewers get? Public TV leaders at NETA predicted Mobile DTV will be used for simulcasts of live TV as well as weather alerts, datacasts of traffic maps and sports scores, radio with pictures and interactive brainstorms yet to come, CPB is backing a PBS experiment with a 24-hour children's TV service.

Though commercial broadcasters are mum about their business plans, said CPB Senior Vice President Mark Erstling, they agree that kidvid is Mobile DTV's "killer app."

There's even hope that Mobile DTV will seduce 18-to-24-year-old "millenials" to watch news and public affairs TV, said Lonna Thompson, general counsel of the Association of Public Television Stations, speaking at the NETA Conference. A survey indicated their level of interest would double, she said, because they'd no longer be "tethered" to a set in the living room.

Mobile DTV may be able to do a tolerable imitation of cable: Planners say broadcasters in D.C. will air at least 20 different Mobile channels during the tryout this spring.

It can also do a limited imitation of video-on-demand by "clipcasting"--constantly downloading, in advance, an array of popular videos to be stored in users' receivers--though it won't let users choose among every video on the Web.

Where it may shine is fulfilling past visions of interactive TV that cable has failed to realize. If the mobile receiver is a cell phone, it can provide a return path for ordering pizzas, voting on American Idol or whatever users want to click

"There will be great businesses built in Mobile DTV," predicted Andy Russell, senior v.p, PBS Ventures, at the NETA Conference. "We think the possibilities are enormous with this new platform." Researchers predict Mobile will generate $1 billion a year in ad sales, with interactivity sweetening the profitability. He anticipates commercial broadcasters' ad sales will rise further when they work out ways to hyperlocalize service, promoting services geographically close to viewers.

There are even revenue enticements for public TV. The FCC regards datacasting as an "ancillary and supplementary" nonbroadcast service, for which public TV stations can earn revenues, said Thompson. The commission would require that the station pay it a 5 percent fee on any such revenues, she said. The station also must maintain a broadcast signal using 4.7 mbps of its bitstream, Kutzner said.

One possibility is that cell carriers will lease capacity on broadcast signals to haul video. Compared to the way some phone companies transmit video, one circuit per viewer, it's an economic winner, said Kutzner. Some cell companies spend $4 an hour per video user for transmission while Mobile DTV in a large market, reaching many viewers at once, would spend 1 cent per viewer\\

Mobile DTV has been under discussion for a decade and OMVC was formed in 2007 and ATSC's standard-setting work began in June 2008. Mobile wasn't dreamt up to help broadcasters keep spectrum, but "it's fortunate we were so far down the road," Kutzner told Current. "It's a very good illustration" of broadcasting's capabilities.

"When [Mobile receivers are] in the consumers' hands, the government won't have the nerve to take them away," said Erstling.

No FCC action is required to approve Mobile DTV, advocates said, because it fits within the DTV standard defined by the Advanced Television Systems Committee.

While wired broadband may be the rational choice to deliver TV to the multitudes in their homes, broadcasting is a rational option for delivering it to receivers on the go.

"It is a great way to provide content that is widely used. It is inherently efficient," Richer said at NETA. "We need to . . . leverage those benefits inherent in broadcasting."

No go for low VHF channels

Mobile isn't an option for stations on the lower VHF channels, Kutzner said at NETA. The physics of broadcasting make it impractical because the antennas to receive Mobile on Channels 2 through 6 would be "so large that they wouldn't make any sense." Higher VHF channels through 13 would be less handicapped. But UHF stations generally can provide excellent coverage within 15 miles and good coverage within 40 miles, he said.

The technology has off-the-shelf aspects. It uses the Internet protocol for transmission, mpeg video and iPod audio. To make the Mobile signal receivable in a speeding vehicle, however, the signal must carry a ton of data for forward error correction. The extra data helps the receiver instantly reconstruct content if it doesn't catch all the bits accurately.

Ordinary DTV for fixed receivers already reserves a third of its bitrate for error correction (the whole broadcast DTV channel accommodates 27 mbps, Kutzner said, not the 19.4 mbps we usually hear about).

For Mobile DTV, the transmitter uses, in addition, 66 percent to 84 percent of the Mobile signal's capacity, for error correction, Kutzner told Current.

For broadcasters, Mobile DTV is an add-on to DTV transmissions.

A broadcaster's big commitment is a portion of the TV channel. Of the total 19.4 megabits per second payload in a standard broadcast channel, a Mobile channel would take about 3 mbps, Kutzner said.

Then there's the cost of accessorizing the transmitter--$75,000 to $200,000, Erstling said at NETA.

It's cheaper for stations with newer transmitters; they may need only a software upgrade. Older transmitters would need a new exciter, mobile multiplexer and a post-processor that cost, altogether, $75,000 to $150,000 for one standard-def channel and $10,000 to $20,000 per each additional channel, Kutzner told Current.

For broadcasters interested in learning more, ATSC will hold a day-long seminar on Mobile DTV Feb. 3, 9 a.m. to 4:30 p.m. in Washington, D.C. The committee's website is taking seat reservations at atsc.org/seminars/mobile10.php.

"You cannot overstate the importance of mobile to broadcasting," said
Mark Richer, president of the Advanced Television Systems Committee...

------

Too bad they didn't realize this when designing/adopting the ATSC system.

Garmin Nuvi 1490TV

I see that Europe announced the Garmin Nuvi 1490TV for that market, I suspect that something like this will be available in the United States if ATSC-M/H ever takes off.

garmin -- NaviGadget

Garmin Nuvi 1490TV Supports Digital Broadcast TV

Garmin nuvi 1490TV adds soaps and sports to GPS | GPS Obsessed

The New York Times - February 15, 2010
Local TV for Devices on the Move
By ERIC A. TAUB

Who has time to sit on the couch and watch TV anymore? In the last 10 years, broadcasters have lost 25 percent of their audience. So to win back some viewers, the industry has a plan to grab their attention while they are on the move.

Beginning in April, eight television stations in Washington, D.C., will broadcast a signal for a new class of devices that can show programming, even in a car at high speed. In all, 30 stations in Atlanta, Chicago, Los Angeles, Seattle and Washington have installed the necessary equipment, at a cost of $75,000 to $150,000.
.....
Full story http://www.nytimes.com/2010/02/15/bu.../15mobile.html

I would suspect that if more TV stations start broadcasting to mobile devices, that woudl hopefully lead to stations upgrading their transmitters and antennas to broadcast over a larger range so both mobile devices and home OTA TV viewers can better reception.

There will soon be yet another choice of GPS DTV for the DVB-T crowd:

http://www.mio.com/miocebit2010/Moov...rtainment.html

What devices are avaliable to receive these Mobile DTV streams and display them today.
What stations around the country are actually broadcasting Mobile DTV channels today?

I should fire up TSreader and check for any new parasitic streams from all my locals.