[opendtv] Re: From Broadcast Engineering - WRAL tests mobile DTV
- From: "Bob Miller" <robmxa@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 8 Aug 2008 06:26:01 -0400
This is getting more confusing. According to John you need 9 mb/s for
two services regardless of whether you are using 1/2 on one and 1/4 on
the other?
The article says they are using a total of 4.5 mb/s with one service
at 1/2 using .6 mb/s and the other service at 1/4 using .3 mb/s. Mark
says the efficiencies are 18% for 1/4 and 36% for 1/2. If .3 mb/s is
18% efficient then 100% is 1.67 mb/s and if .6 mb/s is 36% efficient
then 100% would be 1.67 mb/s for a total of 3.34 mb/s.
3.34 mb/s is 1.16 mb/s shy of 4.5 mb/s and if John is right and you
need 9 mb/s for two services it is 5.66 mb/s shy.
If John is right then for .9 mb/s of programming you need 9 mb/s of bandwidth.
I don't think I ever thought it would be that bad.
If Tom is right as to the article they needed or at least 4.5 mb/s to
transmit .9 mbps or a 20% total efficiency.
If John is right they would need 9 mb/s for the two services totaling
.9 mb/s for an efficiency of 10%,
What am I getting wrong? What don't I understand? Was I wildly
optimistic last year?
Bob Miller
On Fri, Aug 8, 2008 at 2:10 AM, John Willkie <johnwillkie@xxxxxxxxxxxxx> wrote:
> You cannot draw conclusions until the standard has been released. However,
> I believe that public prints have put the o/h at close to 4.5 mb/seconds for
> one service, and IIRC, 9 for 2 services. Maybe the term isn't exactly
> services, but I can only refer to things which have been mentioned publicly.
>
> John Willkie
>
> -----Mensaje original-----
> De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
> nombre de Bob Miller
> Enviado el: Thursday, August 07, 2008 9:09 AM
> Para: opendtv@xxxxxxxxxxxxx
> Asunto: [opendtv] Re: From Broadcast Engineering - WRAL tests mobile DTV
>
> That is what I would like to know. How far was I off last year when in
> technical ignorance but from a good source I put out numbers on what
> one 8-VSB mobile modulation would cost in bits. What are the numbers?
> What is the overhead and what is the % of bits that are real at what
> robustness levels?
>
> Anybody care to compare to DVB-T or H or CDMB-T or is it a big secret
> because it is so bad.
>
> Bob Miller
>
> On Thu, Aug 7, 2008 at 11:24 AM, <dan.grimes@xxxxxxxx> wrote:
>>
>> What is the reason for only getting one 600 Kb/s and one 300Kb/s channel
> out
>> of 4.5 Mb/s? Are the rest of the bits required for overhead or did they
>> just not fill all the M/H channels possible in the 4.5 Mb/s subchannel
>> bandwidth?
>>
>> Dan
>>
>>
>>
>> Tom Barry <trbarry@xxxxxxxxxxx>
>> Sent by: opendtv-bounce@xxxxxxxxxxxxx
>>
>> 08/06/2008 08:41 PM
>>
>> Please respond to
>> opendtv@xxxxxxxxxxxxx
>> To
>> opendtv <opendtv@xxxxxxxxxxxxx>
>> cc
>> Subject
>> [opendtv] From Broadcast Engineering - WRAL tests mobile DTV
>>
>>
>>
>>
>> Supposedly from Broadcast Engineering though I copied it from AVS
>> <http://www.avsforum.com/avs-vb/showthread.php?t=1056025>. I'm not sure
>> I understand it correctly but it looks like they got a total of 900
>> kbps (2 channels, 300+600) after error correction overhead from using a
>> total of 4.5 mbps of the channel bandwidth.
>>
>> - Tom
>>
>> ---------------------------------------------------
>> From Broadcast Engineering - WRAL tests mobile DTV
>> Broadcast Engineering Mobile TV Update
>>
>> WRAL tests mobile DTV
>>
>> Users in Raleigh-Durham reported reliable signal reception in most parts
>> of the station's existing coverage area.
>>
>> WRAL-DT, the CBS affiliate in Raleigh-Durham, NC, owned by Capitol
>> Broadcasting Company (CBC), conducted a series of mobile DTV tests last
>> week using the Mobile-Pedestrian-Handheld (MPH) system promoted by
>> Harris Broadcast and others. Hosted by CBC's New Media Group, the tests
>> featured seven handsets given to station executives living in different
>> parts of the state. Users reported reliable signal reception in most
>> parts of the station's existing coverage area.
>>
>> To kick off the July 21-25 trial, the station hosted a reception last
>> Tuesday in which about 50 participants were driven in a bus around the
>> area with prototype LG Electronics mobile handsets that featured
>> MPH-compatible reception chips inside. Signal reception of two channels
>> (half rate at 600kb/s and one-quarter rate at 300kb/s) using about
>> 4.5Mb/s (including turbo coding) of the station's 19.4Mb/s on-air DTV
>> stream was reportedly strong everywhere they went during the 10-minute
>> ride - even at 70 miles per hour.
>>
>> The goal of the service, according to John Harris, WRAL's director of
>> programming, is to extend the reach of the station's television channel,
>> and make it available everywhere our viewers are. The initial plan is to
>> simulcast the on-air DTV signal. WRAL-TV broadcasts CBS network and its
>> own local programming in the 1080i HDTV format as well as in SD digital.
>>
>> "We're excited about the possibilities," John Harris, WRAL's director of
>> programming, told Broadcast Engineering. "The priority is to offer
>> WRAL's TV signal in another way, in another place. I took one [handset]
>> east of the station and I just kept driving until the signal dropped
>> out. I got pretty far before that happened, so I can see the potential
>> of this service."
>>
>> LG Electronics, Zenith Electronics and Harris, all proponents of the MPH
>> scheme, helped out with the field trials. WRAL-DT uses a Harris Sigma
>> CVD UHF transmitter, with an MPH module, for the weeklong test.
>>
>> In a statement, James F. Goodmon, CEO of CBC, said "mobile DTV
>> broadcasting enables WRAL to better serve our viewers, communities, and
>> advertisers by providing a strong combination of anywhere access,
>> two-way communication, and mobility."
>>
>> In 1996, Harris worked with WRAL-DT as one of the first DTV stations in
>> the country. Two years later, when John Glenn made his historic return
>> to space, Harris worked with WRAL to conduct the first live HDTV
>> broadcast of a space shuttle launch to audiences nationwide. Now, the
>> station is the first to promote mobile DTV service in the state of North
>> Carolina. WRAL predicts that more than 200 million portable devices will
>> be sold in 2008, although few if any will have the necessary MPH
>> reception chips inside.
>>
>> WRAL-TV and Capitol Broadcasting Company are part of the Open Mobile
>> Video Coalition (www.openmobilevideo.com), a nationwide group of
>> broadcasters driving the deployment of mobile digital broadcast
>> television. Commercial deployments are forecast for 2009. The group
>> hopes to have an established standard available to broadcasters by the
>> February 2009 analog shutoff date.
>> --
>> Tom Barry trbarry@xxxxxxxxxxx
>>
>>
>>
>>
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