[opendtv] Mediaflo Technology
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 9 Nov 2006 09:05:00 -0400
At 6:32 PM -0800 11/8/06, John Willkie wrote:
IIRC, they're offering 16-20 linear video (each with two audio)
program services, plus 'clip channels' and a handful of audio and
data services in a multiplex that occupies a 6-mhz channel using 22
or so MBPS per mux.
John is confusing some elements of the system design here. If you
want to fully understand how Flo works, and how it compares with
DVB-H and ISDB, the following Qualcomm whitepaper may be informative:
http://www.qualcomm.com/mediaflo/news/pdf/flo_tech_overview.pdf
The link to this whitepaper and other resources can be found here:
http://www.qualcomm.com/mediaflo/news/resources.shtml
When you work through all the details you will fine the following system specs.
Overall efficiency ~1 bps/Hz
OFDM using 4K symbol mode
A total of 20 channels each with ~ 300 kbps (statistically multiplexed).
Layered modulation combining a base layer that supports 320 x 240 @15
fps with an enhancement layer that brings the frame rate up to 24 or
30 fps. Uses MPEG-4 with streams optimized for an average of 360 kpbs.
The channels will be used as follows:
14 live streaming national interest
5 live streaming local interest
50 national and 15 local services that will deliver ~20 minutes of
content per day to receiver cache.
The system will also deliver IP data services.
By comparison, the whitepaper claims that DVB-H can deliver 9
channels in 6 MHz.
In strong signal areas, the frame rate is 24 or 30 per second;
otherwise, it's 12 to 15 per second. But, remember that those video
channels at best are half the resolution of NTSC, but with image
sharpening technology.
Really? The effective resolution of NTSC is 320 x 240 at 60 fields
per second. With good de-interlacing, I would suggest that these
streams will come close to equaling NTSC quality, however, that is
irrelevant since we are talking about displays in handsets. Apple
started the iTunes video service at this resolution, and the stuff
looks fine when output to an interlaced TV. But the LPTV guys could
deliver something like 640 x 480 @ 60P which would be significantly
higher quality than NTSC, perhaps with a 320 x 240 base layer.
Remember: people don't watch technology, and they tend to seek
quality when it is available and has a wide variety of content.
(This includes the betamax argument, since it wasn't widely
available and had limited variety of content.)
This argument must be tempered with reality. People are consuming
vast amounts of video content via the Internet, most of which is less
than NTSC quality. It is all driven by applications and competition.
Mobile Tv does not need to equal the family room viewing experience.
Regards
Craig
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