[opendtv] Re: New Philips HDD/DVD recorder

And, multiple language audio services weren't all that common a decade ago
(in the U.S.), but they are rather common now, and seem to be more common as
time goes on.

Add to Mark's bit-budget (for single decoders) descriptive video.  Perhaps
one service will work, but more likely you'll need one with main program
audio mixed in at the same level as descriptive video, and another with
descriptive video at a lower level than main program audio.

With dual decoders, the 'viewer' who uses this type of service could mix the
audio level at home, dynamically.  

A good friend of mine could use this service.  Due to diabetes, he lost his
sight about four years ago.  He still has his 4dtv sat unit and cable
subscription, and he still 'watches' tv.  He just never gets the sight gags
and things that are not referred to in the audio track.

My friend is also English-Spanish bilingual ... he would have no little
problem listening to the main program in English and descriptive video in
Espanol.

A small subset of viewers would benefit from descriptive video, but it would
be a way to distinguish program offerings.  Without dual decoders,
broadcasters are unlikely to offer descriptive video without being forced to
do so; the bit budget is just too much, and the penalty is multiplied by the
number of virtual channels.  So, it would be less of a problem for Fox or
CBS, but more significant for PBS stations, which generally offer multiple
channels in their transport streams.

John Willkie

-----Mensaje original-----
De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
nombre de Mark Schubin
Enviado el: Thursday, December 27, 2007 2:39 PM
Para: opendtv@xxxxxxxxxxxxx
Asunto: [opendtv] Re: New Philips HDD/DVD recorder

A 5.1-channel audio package might take 384 kbps (I prefer 448).  Mono 
audio might be 64 kbps.

So, a 5.1-channel VI package (audio for the visually impaired) takes 384 
kbps, and a 5.1-channel undescribed CM (complete mix) package takes 384 
kbps.  Together, they take 768 kbps out of the channel.  On the other 
hand, a mono description (VI) added to a 5.1-channel complete mix (CM) 
is just 448 kbps, a savings of 320 kbps.

Now consider other viewers.  A 5.1-channel music & effects package (ME) 
might take 384 kbps, which, combined with a 64 kbps English-language 
dialogue (D) channel comes to 448 kbps, worse than just the CM.  But add 
Spanish 5.1, and the two CMs would take 768 kbps; 2D+ME is just 512 
kbps.  Add French to that (as you might want to do in Miami, where the 
three languages are commonly spoken), and it's 3CM at 1.2 Mbps versus 
3D+ME at 576 kbps.  Add more languages, and the bit-rate advantage 
increases for the dual decoders.

Or try a science show with multiple commentary channels.

But broadcasters cannot do it, even though it's perfectly okay in the 
standard, because (unless things have changed recently) not a single 
dual-stream audio decoder has been sold.

TTFN,
Mark


 
 
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