[opendtv] Re: PR: Enhanced AC-3 Audio Specifications Serve Mu ltiple Applications
- From: "jmwillkie@xxxxxxx" <jmwillkie@xxxxxxx>
- To: Keith Jack <Keith_Jack@xxxxxxxxxxxx>, opendtv@xxxxxxxxxxxxx,opendtv-bounce@xxxxxxxxxxxxx
- Date: Thu, 8 Apr 2004 14:05:27 -0700 (PDT)
Well, because you don't want the streams to be mixed in the encoder or
upstream. The idea is to do the mixing based on viewer preferences. As for
the rest, you'll have to ask a Dolby engineer.
Once DTV starts generating revenues, broadcasters will want to have
redundancy in AC-3 encoders. Brute force is sometimes the only way to
insure redundancy.
Back to the point, in a dual-encoder/dual-decoder environment, one can use
one Music + Effects channel and combine it with any number of monolingual
center (or dual audio) tracks for individual languages. The savings, per
language service, over your scenario is over 300K bits per second. On the
receiver side, aside from having dual decoders, the max bit rate for the
combined streams is 576K, versus 448K for singl-stream audio.
John Willkie
Keith Jack <Keith_Jack@xxxxxxxxxxxx> writes:
>Why not just design the Dolby decoder to handle two or three input
streams,
>mix the results and output it? Using two decoders seems rather brute
force.
>
>
>-- Keith
>
>
>> -----Original Message-----
>> From: John Shutt [mailto:shuttj@xxxxxxxxx]
>> Sent: Thursday, April 08, 2004 11:52 AM
>> To: opendtv@xxxxxxxxxxxxx
>> Subject: [opendtv] Re: PR: Enhanced AC-3 Audio Specifications
>> Serve Multiple Applications
>>
>>
>> Mark,
>>
>> Then I stand corrected. It was always my understanding of
>> the Urban Myth that the STB box manufacturers didn't want to
>> spend the extra money for a second Dolby Decoder. If Dolby
>> offered to allow the second decoder for no extra license fee,
>> then I am at a loss as to why STB manufacturers did not build
>> in the functionality from day one.
>>
>> The real fault lies with the ATSC in not making dual decoders
>> a MUST rather than a MAY, as you allude to.
>>
>> The real, real fault lies in adopting a standard that is
>> still evolving, yet must maintain backwards compatibility to day one.
>>
>> The only people that will ever use dual audio stream mixing,
>> directed channel change, or any of the other "goodies" stuck
>> onto the standard after the first generation boxes were
>> deployed will be closed system providers like USDTV who can
>> have their boxes custom built to their specs.
>>
>> Cheers,
>>
>> John Shutt
>>
>> ----- Original Message -----
>> From: "Mark Schubin" <tvmark@xxxxxxxxxxxxx>
>>
>> > We are in complete agreement about the problems of single-stream
>> > decoders
>> in ATSC receivers, but I think
>> > you might be off-base in blaming Dolby. They fought for mandatory
>> dual-stream, and, I think, were willing
>> > to allow the second decoder fee-free. My understanding is
>> that, when
>> > they
>> couldn't get the mandatory
>> > dual-stream status, they did decide to charge for the
>> second but much
>> > less
>> than for the first.
>> >
>> > TTFN,
>> > Mark
>>
>>
>>
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