Re: the cold hard facts about mp3 sound quality
- From: Keith <k_gubitz@xxxxxxxxx>
- Date: Sat, 02 Jun 2007 18:17:51 GMT
On Fri, 01 Jun 2007 14:59:09 GMT, really real <reallyreal@xxxxxxx>
wrote:
From yesterday's New York Times, the newspaper that publishes all the
news that figures.
Where?s the Other Half of Your Music File? By WILSON ROTHMAN
CHANCES are that even if you have taken the plunge and started building
a digital music collection, you have never had to tangle with the word
?bitrate.? That may be about to change.
The Apple iTunes store, the largest seller of music downloads, began
selling tracks from EMI Music yesterday without any restrictions on
copying, for a slightly higher price than usual, $1.29 instead of 99
cents. To sweeten the deal, those tracks have better sound, with a
bitrate of 256 kilobits per second (kbps), up from the standard 128
kbps. Apple has gone so far as to say that this results ?in audio
quality indistinguishable from the original recording.?
So what exactly is a bitrate? Simply put, it is a measure of the amount
of data used to represent each second of music. A higher number means
that more sonic information can be used to recreate the sound. To
careful listeners, or those with good audio equipment, more data can
make a big difference.
Last fall, Dr. Naresh Patel, a physician in Fort Wayne, Ind., moved into
a home he designed with his wife, Valerie. It has a home theater,
complete with projector, surround-sound speakers and a high-end
amplification system. The sonic centerpiece is two Bowers & Wilkins
loudspeakers that cost Dr. Patel $12,000 ?with a discount.?
It was all working beautifully until Dr. Patel connected his iPod to the
system. Sitting down in the theater?s sweet spot to enjoy his music, he
was instead appalled.
?I couldn?t believe what I heard,? he said. ?You don?t need a trained
ear to hear the complete lack of so many things: imaging, the width and
the depth of the sound stage. It almost sounded monaural, like listening
to music in mono. The clarity, silkiness, the musicality of the music,
if you will, was not there.?
The problem was compression ? the process of removing audio data to fit
the music into a smaller file. Compressed audio making audiophiles
crinkle their noses is not surprising, nor is it new. It has its roots
in the debate of the 1980s, pitting the digital CD against the beloved
analog vinyl record. The degradation of CD quality into something even
more limited is simply proof to many fervent music listeners that
Armageddon is indeed at hand.
But several factors are making the debate over sound quality and
bitrates more relevant now. Digital storage is cheaper than ever,
download speeds are increasingly fast and digital music files have taken
the place of CDs in many home theaters and cars. Many people are
specifically asking for higher-quality downloads, and Apple and other
online retailers are eager to deliver them ? for a higher price, of
course. (The price of complete albums from iTunes in the higher-quality
format will remain the same.)
Barney Wragg, who oversees EMI?s global digital music efforts, said
there had been a shift in the music marketplace. ?What was an entirely
PC, MP3-player experience has changed; now people are wiring music via
iPods into their stereos in their home and their car,? he said. ?That?s
what is driving the demand for increased fidelity. When I connect an
iPod directly into the hi-fi in my car, I really notice the difference.?
Apart from bitrate, the sound quality of digital music is also affected
by its format, which is determined by the software used to compress it,
known as a codec. MP3 is one of the older techniques for compressing
audio and is not widely used by online stores. Apple has chosen a newer
format called Advanced Audio Coding (AAC), which plays on iPods and some
other devices. Most other online stores use the similarly modern Windows
Media Audio, or WMA, which does not play on iPods.
All three of these formats are ?lossy,? meaning the encoding software
surgically trims out audio information that is not easy to hear, because
it is covered up by other sound or is situated at the highest and lowest
ranges of human hearing. The Norah Jones track ?Come Away With Me? is
33.4 megabytes when stored in an uncompressed format; the lossy
compression methods bring that down to 6.1 megabytes at 256 kbps, or 3.1
megabytes at 128 kbps, regardless of the codec used. (When turning your
CDs into song files on your PC, you can choose the bitrate you want in
the settings of iTunes or Windows Media Player.)
Codecs do vary in quality. Mr. Wragg of EMI said that as a rule of
thumb, an MP3 at 320 kbps is roughly the same as an AAC file at 256
kbps. ?The difference between WMA and AAC is more difficult to say,? he
added. ?Each has a slightly different way of getting compression. But in
double-blind tests they perform pretty similarly ? bitrate for bitrate
they sound similar, but some prefer one over the other.?
Until now, online retailers have dealt in 128 Kbps tracks ? most
retailers, that is. Two years ago, a group of audiophiles created
MusicGiants, a digital download store that specializes in ?lossless?
files that are compressed in a way that does not discard any audio
information, resulting in tracks that average 25 megabytes in size.
MusicGiants now has more than 500,000 songs from most major labels.
Scott Bahneman, chief executive of MusicGiants, said that comparing
lossless tracks and compressed tracks was like comparing photos taken
with a high-end digital camera and those taken with a camera phone.
?Every bit counts when you?re trying to get sound quality, resolution or
anything else,? he said. The site?s core audience is the type of person
who spends large sums of money on home theater equipment, and wants
music stored as digital files rather than on CD.
Mr. Bahneman said his company planned to offer better-than-CD-quality
music in files originally created for the DVD-Audio and Super Audio CD
disc formats, which did not catch on with consumers. Each song will be
250 megabytes, about the same size as one episode of a sitcom on iTunes,
but without the video. These ?Super HD? files will have a bitrate of up
to 11,000 kbps (that is, 11 megabits per second), and will be sold by
the album rather than the track, at $20 each. Mr. Bahneman said that
with the latest broadband services and huge hard drives, downloading and
storing high-resolution audio files should not be a big hurdle.
MusicGiants? giant files are unlikely to appeal to the masses. Most
people agree that on run-of-the-mill headphones, car speakers and
compact sound systems, it is not easy to tell a low bitrate from a high
one, because what is lost in compression is also lost in the
reproduction of sound through those kind of speakers.
To test the effect of different bitrates, I borrowed a sound system that
was not an audiophile?s wildest dream, but was certainly higher quality
than the gear owned by most music buyers: a Harman Kardon AVR 147
receiver ($449) and two JBL L880 speakers ($1,400 a pair), connected to
an iPod via the Harman Kardon Bridge adapter ($70).
This unscientific study involved three people (including myself) who
listen to music daily in a variety of formats, from FM radio to CD. I
loaded an iPod with 11 versions of ?Come Away With Me,? spanning various
qualities of MP3 and AAC from 64 kbps to 320 kbps, as well as one in
Apple?s lossless format. Sitting in the sweet spot, we each listened to
the different versions, played in random sequence, trying to determine
if each subsequent version was higher or lower in quality. It was a
straightforward test, and the result was surprising.
The difference between 64 and 128 kbps was stark. All three of us picked
up on it. As bitrates climbed above 128 kbps, however, our guesses
became increasingly haphazard; none of us could determine the difference
between 320 kbps and lossless. One unexpected result was that we all
thought low-bitrate AAC files sounded better than low-bitrate MP3s.
Still, even if poorer-quality tracks do not sound so terrible to all
listeners, the difference between 128 kbps and 256 kbps is real. Many
people will spend extra money for better-quality merchandise, perhaps in
anticipation of a future sound-system upgrade. You may not buy all of
your downloaded tracks a second time at higher quality, but you may
decide that from now on $1.29 is a fair price to pay for an improved track.
Dr. Patel said he had mixed feelings. He said he would always prefer CD
quality to compressed audio, even at 320 kbps. Will the higher-quality
downloads from iTunes matter? ?I?ll take the best of what I can get,? he
said, ?but I?m not terribly excited because it?s not that much of an
improvement.?
I told ya, I told ya!
Now if that Doctor started spinning vinyl he would be spouting a new
story, CD's suck too!
.
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- From: really real
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