[opendtv] Re: PR: Enhanced AC-3 Audio Specifications Serve Multiple Applications
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 8 Apr 2004 09:33:55 -0400
E-AC-3 is not compatible with existing receivers, and as such, will only be
used in the robust portion of the E-VSB bitstream. This is simply Dolby's
attempt to keep their exclusive lock on the audio codec of ATSC and the
resulting royalties.
It was Dolby that refused to grant a license for an unlimited number of
decoders in an ATSC box, which led all STB manufacturers to only include one
AC-3 decoder, thus rendering useless almost all of the flexibility built
into the ATSC standard for audio, including the ability to mix a second
language dialog channel with a generic music channel, or the ability to mix
voice overs inside the STB instead of at the studio.
The robust portion of the E-VSB signal is very cramped for bits, and there
are more efficient coding schemes available than AC-3. Given that the robust
portion of E-VSB is really aimed at the small screen portable receiver, more
compromise can be reasonably made in the audio codec.
I was very impressed with the newest audio codecs from Ibiquity Digital for
use with "HD Radio." Very good near-CD quality stereo audio at 96 Kbps,
and very decent Analog FM quality stereo audio at 64 Kbps. I was even more
impressed by the improvements made to the AM IBOC codecs at 32 Kbps. Any of
which are more than adequate for 2" speakers.
Wake up ATSC! Make sure that when you specify an audio codec for E-VSB, it
is the best available, not just the one offered by the double-D. But then
it won't matter, as no broadcaster will adopt E-VSB anyway.
Cheers,
John Shutt
----- Original Message -----
From: "Craig Birkmaier" <craig@xxxxxxxxx>
> Enhanced AC-3 Audio Specifications Serve Multiple Applications
>
> WASHINGTON, D.C., April 7, 2004 - The <http://www.atsc.org/>Advanced
> Television Systems Committee (ATSC) has published two new Candidate
> Standards that document enhancements to the AC-3 digital audio
> compression standard and specify its use in the DTV Standard. The new
> specifications will provide improved performance and flexibility.
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