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Special - ATRAC Developer's Interview

ATRAC: Answering Today's Needs

-What was behind the development of ATRAC3plus?

Inoue : We developed ATRAC3plus at a time when it seemed we had to answer a variety of demands - including both low bit rates and high bit rates.

Toyama : The ATRAC3 specification was originally developed to achieve a sound quality equivalent to the MiniDisc at 132kbps, so there was a limit to what kind of quality we could expect at a lower bit rate. But we applied technologies to solve the various obstacles we had faced in the past and focussed on crafting a new sound that would satisfy changing demands. ATRAC3plus is the result. In subjective evaluation tests conducted by third parties in 2003, it was confirmed that ATRAC3plus at 64kbps offers sound quality equivalent to MP3 at 128kbps.

Inoue : The demand for low bit rates started to coincide with the capacity increase of hard disk drives and other storage media, which meant, for some people, that a high compression ratio was not the most important criterion, as long as they could record with high quality.

Suzuki : Yes. Users who put more emphasis on sound quality than on the number of tracks.

Inoue : The answer for them is ATRAC3plus at 256kbps. CDs are 1,411kbps, so we are talking about 1/5 the size, but audio quality is almost as good as the original CD.

Toyama : In recent subjective evaluation tests, we proved that it's almost impossible to tell the difference in sound quality between ATRAC3plus at 256kbps and CDs at 1,411kbps.

 


ATRAC: Our Ears Did the Talking!

-You were talking about crafting the sound, but how do you go about optimizing or tuning?

Suzuki : Sound is subjective. Something about a particular sound may really grab your attention, yet someone else won't even notice it. When that happens, you get friends of like mind together and make that someone feel bad! (laughter)

Toyama : For example, people who play instruments tend to pay attention to the sound of each instrument, but your average person enjoys music as an overall experience. Everyone listens to music differently, so it's dangerous for just one person to do the tuning. I've played a variety of instruments, so when I listen to music I pay attention to how they sound, and the quality of vocals as well.

Suzuki : I'm the opposite. I listen to the whole thing. I belong to the generation that grew up with Walkman - music accompanies my activities. I don't notice the parts, but take in the whole song. As you can see, even within our team, we listen to music differently. But we don't give priority to one type of listening. It's important to find the best balance - that's our approach. So whenever I make progress in crafting sound, I get Tsuji and Inoue to join me in the listening room for several hours to get their opinions.

-What exactly is involved in this process of tuning?

Suzuki : We repeatedly encode and decode. In other words, we process the signal, compress it, reconstitute it and then listen to it again. Usually we use headphones, but when doing an overall check we pipe it through speakers in the listening room.

-Is there a difference between listening on headphones and listening through speakers?

Suzuki : Oh, completely different. To check details of the sound, headphones are the thing. But speakers are essential when you want to check the ambiance, harmonious sound, balance, and so on. You may think you've achieved a really beautiful sound, only to find that in an open listening space, that's not the case.

Tsuji : And because our constant tweaking is affected by our surroundings, we can't work in an open-plan layout to do our tuning. Our workspace isn't very large, but it's divided up with high partitions.

Suzuki : When tuning, we use a database of sound sources created especially for evaluation. For example, Mariah Carey is extremely tricky because the instruments and the vocals range over a very wide spectrum. And we can't make an encoder by just targeting a particular band. I've been listening to Mariah for 8 years - tens of thousands of times. Now I don't need to listen to the original sound source: just listening to the decoded sound I can tell whether it's good or not. I think her songs are indelibly impressed on my memory.