[opendtv] Re: Mobile TV: $2 Billion in Ad Buys
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sat, 19 Apr 2008 19:01:08 -0400
John Shutt wrote:
> If I correctly understand DVB-H when applied to a DVB-T stream, DVB-H in
> and of itself doesn't incur a bitrate penalty to the DVB-T transport
> stream.
Doesn't it? I at first thought so but it seemed that Bert had been
studying this and claimed AVSB had similar spectral efficiency. And I
thought the spectral efficiency was the measure of the number of data
bits delivered after subtracting the overhead for FEC, synchronization,
etc. (actual delivered data payload b/s/Hz)
-------------------------------------------------------
So I don't know the correct answer but it seems you can't both be right
unless I am misunderstanding at least one of you.
- Tom
----- Original Message ----- From: "John Willkie"
<johnwillkie@xxxxxxxxxxxxx>
If I have been able to read through the interlineations, we are in
general
agreement.
1) two-way is better that one way, and
2) mobile tv will work better if it's not just mobile video and
3) A-VSB seems to use a big overhead.
Yup, we are in violent agreement.
(my criticisms have ALWAYS been of mobile video, not mobile TV)
Judging by the number of DVD systems sold by OEM auto manufacturers, I'd
say mobile video entertainment is the only segment of the mobile video
market that has actually made money, since the profit is made at the
time of sale.
Without doing a spreadsheet on it, devoting 11% of your transport
stream to
serve mobile audiences seems much better than the hit in going to DVB
with
receiver/confusion issues (there being only one ATSC/DVB set on the
market
-- at least that I've seen).
With the exception of occasionally messing with Bert, I fully appreciate
it is long past the point where DVB-T is a viable alternative to ATSC in
the US. The point of no return in my opinion was the FCC tuner mandate.
However, I'd rather have had the choice of sacrificing 11% of my
transport stream to make the other 89% receivable by all devices mobile
and fixed, rather than sacrificing 11% of my transport stream to make
less than 5% of the total potential bitrate receivable by portable
devices only, and not receivable at all by legacy home devices.
I believe Bob Miller's infamous demo was at around 17 Mbps. The demo is
still up at www.viacel.com/bob.wmv. That reception, while far from
perfect, was more than adequate for backseat viewing, and was receivable
by all fixed receivers as well. No either/or choice of bitrate allocation.
If I correctly understand DVB-H when applied to a DVB-T stream, DVB-H in
and of itself doesn't incur a bitrate penalty to the DVB-T transport
stream. It just provides a predictible time slice to offer related
program data packets, so the receiver can turn on and off at regular
intervals, saving battery power. DVB-H as implemented here in the US is
slightly different, as the video resolutions are geared to handheld
screens, and the carrier frequency is well outside of the US television
band. (And I think the channel is narrower than 6 MHz as well.)
The other DVB-T solution for mobile reception was HM-COFDM, but that was
fairly rigid in the amount of robust vs. high capacity bitrates
available, but the bitrate hit vs. the number of robust bits transmitted
is lower than any of the ATSC proposals I've seen.
The DVB HM-COFDM demo at the 2000 NAB delivered 4.5 Mbps of robust
mobile data, and about 13.5 Mbps for the main service, in a 6 MHz
channel. If your baseline is 19.4 Mbps, That's about 1.4 Mbps of lost
payload (7%) and in return you deliver 4.5 Mbps (23%) to mobile devices
AND to legacy fixed devices. (All DVB-T chipsets support HM COFDM modes
so legacy fixed receivers can tune the robust bits.)
However, all of that is a moot point for the US, so we're counting on
your work on the ATSC committes to deliver us the best possible M/H
standard.
While I was at the convention, I asked about HD Radio. As one
example, the
folks at C.Crane -- with two HD radio sets, none on display -- said
they had
sold very, very few. This in the second year of a very aggressive
push to
HD Radio units in advertising channels.
Strange. Our listener is very happy with his HD radio. Seriously, HD
radio is at the same point that ATSC was 5 years ago. We're on a first
name basis with our listeners.
HD radio is not going to take off until it is commonly offered in OEM
car radios, which should happen in the next 1 to 2 years. (I'm sure
availability in OEM radios was a big factor in the penetration of
satellite radio.) After that, HD Radio will have all the success of AM
Stereo...
John
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Tom Barry trbarry@xxxxxxxxxxx
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