[opendtv] Re: The New Mac Mini is All About Movies
- From: "Donald Koeleman" <donald.koeleman@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Tue, 25 Jan 2005 14:29:09 +0100
http://www.slate.com/id/2112548/
You Can't Be Too Thin
The skinny new audio format that will replace MP3s-and revolutionize
Internet radio.
By Paul Boutin
Posted Friday, Jan. 21, 2005, at 4:44 PM PT
It's a given that fat broadband lines are the future of online media. But
right now, for Internet radio, the future is about slimming down-creating
skinny little streams of data that don't eat up too much bandwidth. The key
is a new and better audio compression format called aacPlus, or sometimes
HE-AAC, which has been chosen by the industry committee that standardized
MP3 13 years ago (the Motion Picture Experts Group). If you've tried to
listen to online stations, you know they sound grainy if they're streamed at
any less than 128 kilobits per second-maybe 96 kbps if you're not fussy.
That makes a broadband connection a must. But aacPlus sounds nearly as good
as a CD, even when it's compressed enough to play through a dialup line.
Don't take my word for it-see the results of the European Broadcasting
Union's listener tests, in which aacPlus was deemed the "clear winner" at a
dialup-friendly 48 kbps.
AacPlus has been around for a while-it's what XM satellite radio has used
from the outset-but recently it's been gaining ground. Future digital music
players will support the format just as surely as they do MP3, but you don't
have to wait-you can listen to it right now. Install the free Winamp player,
which added aacPlus support a few months ago. Then click through the
channels on the Tuner2 Web site, which all stream aacPlus sound at 48 kbps
or less. I've spent a week comparing them to the higher bandwidth stations
served by the big three of Net radio-Yahoo, AOL, and MSN-and only Yahoo's 96
kbps premium subscription channels sound as good. For a tour, skip Tuner2's
glut of techno stations and instead try Groove Salad for laid-back
electro-lounge music, Radio Paradise for classic rock, and Sky.FM's Mostly
Classical channel. (If you're on a Mac or other non-Windows computer,
install the free VLC player instead of Winamp.)
It seems crazy until you try it, but Mostly Classical proves that aacPlus
can sound great at 24 kbps. At 48 kbps, it's almost as crisp as a CD. At 128
kbps, it can deliver 5.1 channel surround sound. AacPlus works by combining
three technologies, each of which shrinks the size of an audio signal. The
first is AAC, the Advanced Audio Coding technique that Apple licensed from
Dolby for iTunes. AAC analyzes the sound and throws away any data it knows
human ears won't be able to hear, which is a lot. Then, aacPlus adds
Spectral Band Replication, which strips out all of the music's high
frequencies and replaces them with a tiny bit of analytical data. AacPlus
players reconstruct the highs as a mathematical function of what's left. As
a final space-saving trick, aacPlus tracks are recorded in parametric
stereo. Instead of a left and a right channel, one channel is the sum of the
left and right signals (L+R), and the other is their difference (L-R). This
takes up less bandwidth, and the player can easily flip the two channels
back to the original left and right. (Bonus trivia: This is how FM stereo
broadcasts work.)
Why bother with all this trickery when cheap broadband is spreading
everywhere? There are two good reasons. For station owners, lower bandwidth
means lower costs. Webcasters spend most of their money paying for network
traffic. A station that serves MP3 streams to a thousand listeners at a time
can run up a $4,000 monthly bill. Downsizing from 128 kbps to 24 knocks that
down to around $1,000. The result: More sites will be able to afford to
serve more channels to more listeners, creating a sort of anti-Clear Channel
effect. To get an idea just how much variety is already out there on Net
radio, spend a few minutes randomly searching Shoutcast's 8,000-channel
directory. You can hunt down obscure genres like Ghanaian hilife, listen to
alternative newscasters on Radio Chomsky, and check what's playing on nine
dozen '80s channels instead of one. Most of these stations broadcast in MP3
format. Imagine what'll happen when the cost of Webcasting goes down by a
factor of two, three, or four as aacPlus players become the norm.
Just as important, low-bandwidth stations can reach us in places where we
can't get a 128 kbps connection. Today that includes homes with dial-up
lines, offices where co-workers share a DSL or T1 connection, and the
not-so-speedy Wi-Fi link to my roof. But there's a huge audience looming on
the horizon: cellular subscribers. Gadget makers plan to build aacPlus
players into 3G phones, PDAs, laptops with cellular modems, maybe even car
systems, which could one day tune in to cellular towers instead of
satellites, and stream music that actually sounds good straight from the
Net. Drivers get excited about 130 channels, but imagine how psyched they'll
be with 13,000. Soon, I'll be able to listen to Groove Salad without being
stuck at my desk.
Paul Boutin is a Silicon Valley writer who spent 15 years as a software
engineer and manager.
Photograph on Slate's home page © Royalty-Free/Corbis.
----- Original Message -----
From: "Rob Koenen (ieee)" <rob.koenen@xxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Monday, January 24, 2005 11:15 PM
Subject: [opendtv] Re: The New Mac Mini is All About Movies
John:
> > > Are you misusing words again, or is AAC now (your
> > > "example") an open standard?
Rob:
> > Is your question really whether MPEG Advanced Audio Coding is
> > an open standard?
Tom:
> It is to my knowledge.
Rob:
Then this is a no-brainer ... also see
http://www.marketwire.com/mw/release_html_b1?release_id=79499
Rob
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