[opendtv] Re: New Philips HDD/DVD recorder
- From: "John Willkie" <johnwillkie@xxxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 28 Dec 2007 19:32:03 -0800
Actually, all dialog(ue) is mono, and in the center channel, in AC-3 (unless
down-mixed to stereo). With the caveat that it is possible to put dialogue
(say, for a speaker that is to the left of center in the screen) on one side
or another. However, this is sub-optimal.
As for your scenario, I believe that one cannot do that and be in compliance
with the Dolby AC-3 license. And, if you want a fun time, try dealing with
the Dolby licensing folk. :-) (I've had round or two, and I am a licensee,
but it appears that I don't need a license for what I do, hence no royalty
payments.)
There's an awful lot of flexibility with AC-3, but without dual-audio
decoders, one needs to add entire services instead of mixing and matching.
John Willkie
-----Mensaje original-----
De: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] En
nombre de Albert Manfredi
Enviado el: Friday, December 28, 2007 7:09 PM
Para: opendtv@xxxxxxxxxxxxx
Asunto: [opendtv] Re: New Philips HDD/DVD recorder
Mark Schubin wrote:
> 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.
I would think your second choice is how descriptive service would be
transmitted. No sense duplicating all of the dialogue and background music,
no? (And this applies to each subchannel.)
> 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.
The only problem is that now all dialogue is mono. And, I gather, this isn't
backward compatible with current receivers.
> 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.
In short, multilingual service in full 5.1 for each language is the real
issue here. Because broadcasters can't transmit this efficiently, given that
separate dialogue-only channels would be incompatible with existing
receivers.
Here's a thought.
For multilingual 5.1 to be compatible with existing single-audio-decoder
receivers, one could sell stand-alone audio receivers that take in the
standard English 5.1, store it briefly, mix in a replica of the English
dialogue precisely 180 degrees out of phase, then add in the separate
foreign language D channel(s) as required. This subtracts the English
dialogue without affecting the music and effects. And costs 64 Kb/s for each
foreign language.
Or just offer a mono sound track for all foreign languages, as I believe is
done with analog SAP.
Bert
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